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# Copyright (c) 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
#
from binascii import crc32
import boto
from boto.compat import json
from boto.connection import AWSQueryConnection
from boto.regioninfo import RegionInfo
from boto.exception import JSONResponseError
from boto.dynamodb2 import exceptions
class DynamoDBConnection(AWSQueryConnection):
"""
Amazon DynamoDB
**Overview**
This is the Amazon DynamoDB API Reference. This guide provides
descriptions and samples of the low-level DynamoDB API. For
information about DynamoDB application development, go to the
`Amazon DynamoDB Developer Guide`_.
Instead of making the requests to the low-level DynamoDB API
directly from your application, we recommend that you use the AWS
Software Development Kits (SDKs). The easy-to-use libraries in the
AWS SDKs make it unnecessary to call the low-level DynamoDB API
directly from your application. The libraries take care of request
authentication, serialization, and connection management. For more
information, go to `Using the AWS SDKs with DynamoDB`_ in the
Amazon DynamoDB Developer Guide .
If you decide to code against the low-level DynamoDB API directly,
you will need to write the necessary code to authenticate your
requests. For more information on signing your requests, go to
`Using the DynamoDB API`_ in the Amazon DynamoDB Developer Guide .
The following are short descriptions of each low-level API action,
organized by function.
**Managing Tables**
+ CreateTable - Creates a table with user-specified provisioned
throughput settings. You must designate one attribute as the hash
primary key for the table; you can optionally designate a second
attribute as the range primary key. DynamoDB creates indexes on
these key attributes for fast data access. Optionally, you can
create one or more secondary indexes, which provide fast data
access using non-key attributes.
+ DescribeTable - Returns metadata for a table, such as table
size, status, and index information.
+ UpdateTable - Modifies the provisioned throughput settings for a
table. Optionally, you can modify the provisioned throughput
settings for global secondary indexes on the table.
+ ListTables - Returns a list of all tables associated with the
current AWS account and endpoint.
+ DeleteTable - Deletes a table and all of its indexes.
For conceptual information about managing tables, go to `Working
with Tables`_ in the Amazon DynamoDB Developer Guide .
**Reading Data**
+ GetItem - Returns a set of attributes for the item that has a
given primary key. By default, GetItem performs an eventually
consistent read; however, applications can specify a strongly
consistent read instead.
+ BatchGetItem - Performs multiple GetItem requests for data items
using their primary keys, from one table or multiple tables. The
response from BatchGetItem has a size limit of 16 MB and returns a
maximum of 100 items. Both eventually consistent and strongly
consistent reads can be used.
+ Query - Returns one or more items from a table or a secondary
index. You must provide a specific hash key value. You can narrow
the scope of the query using comparison operators against a range
key value, or on the index key. Query supports either eventual or
strong consistency. A single response has a size limit of 1 MB.
+ Scan - Reads every item in a table; the result set is eventually
consistent. You can limit the number of items returned by
filtering the data attributes, using conditional expressions. Scan
can be used to enable ad-hoc querying of a table against non-key
attributes; however, since this is a full table scan without using
an index, Scan should not be used for any application query use
case that requires predictable performance.
For conceptual information about reading data, go to `Working with
Items`_ and `Query and Scan Operations`_ in the Amazon DynamoDB
Developer Guide .
**Modifying Data**
+ PutItem - Creates a new item, or replaces an existing item with
a new item (including all the attributes). By default, if an item
in the table already exists with the same primary key, the new
item completely replaces the existing item. You can use
conditional operators to replace an item only if its attribute
values match certain conditions, or to insert a new item only if
that item doesn't already exist.
+ UpdateItem - Modifies the attributes of an existing item. You
can also use conditional operators to perform an update only if
the item's attribute values match certain conditions.
+ DeleteItem - Deletes an item in a table by primary key. You can
use conditional operators to perform a delete an item only if the
item's attribute values match certain conditions.
+ BatchWriteItem - Performs multiple PutItem and DeleteItem
requests across multiple tables in a single request. A failure of
any request(s) in the batch will not cause the entire
BatchWriteItem operation to fail. Supports batches of up to 25
items to put or delete, with a maximum total request size of 16
MB.
For conceptual information about modifying data, go to `Working
with Items`_ and `Query and Scan Operations`_ in the Amazon
DynamoDB Developer Guide .
"""
APIVersion = "2012-08-10"
DefaultRegionName = "us-east-1"
DefaultRegionEndpoint = "dynamodb.us-east-1.amazonaws.com"
ServiceName = "DynamoDB"
TargetPrefix = "DynamoDB_20120810"
ResponseError = JSONResponseError
_faults = {
"ProvisionedThroughputExceededException": exceptions.ProvisionedThroughputExceededException,
"LimitExceededException": exceptions.LimitExceededException,
"ConditionalCheckFailedException": exceptions.ConditionalCheckFailedException,
"ResourceInUseException": exceptions.ResourceInUseException,
"ResourceNotFoundException": exceptions.ResourceNotFoundException,
"InternalServerError": exceptions.InternalServerError,
"ItemCollectionSizeLimitExceededException": exceptions.ItemCollectionSizeLimitExceededException,
}
NumberRetries = 10
def __init__(self, **kwargs):
region = kwargs.pop('region', None)
validate_checksums = kwargs.pop('validate_checksums', True)
if not region:
region_name = boto.config.get('DynamoDB', 'region',
self.DefaultRegionName)
for reg in boto.dynamodb2.regions():
if reg.name == region_name:
region = reg
break
# Only set host if it isn't manually overwritten
if 'host' not in kwargs:
kwargs['host'] = region.endpoint
super(DynamoDBConnection, self).__init__(**kwargs)
self.region = region
self._validate_checksums = boto.config.getbool(
'DynamoDB', 'validate_checksums', validate_checksums)
self.throughput_exceeded_events = 0
def _required_auth_capability(self):
return ['hmac-v4']
def batch_get_item(self, request_items, return_consumed_capacity=None):
"""
The BatchGetItem operation returns the attributes of one or
more items from one or more tables. You identify requested
items by primary key.
A single operation can retrieve up to 16 MB of data, which can
contain as many as 100 items. BatchGetItem will return a
partial result if the response size limit is exceeded, the
table's provisioned throughput is exceeded, or an internal
processing failure occurs. If a partial result is returned,
the operation returns a value for UnprocessedKeys . You can
use this value to retry the operation starting with the next
item to get.
For example, if you ask to retrieve 100 items, but each
individual item is 300 KB in size, the system returns 52 items
(so as not to exceed the 16 MB limit). It also returns an
appropriate UnprocessedKeys value so you can get the next page
of results. If desired, your application can include its own
logic to assemble the pages of results into one data set.
If none of the items can be processed due to insufficient
provisioned throughput on all of the tables in the request,
then BatchGetItem will return a
ProvisionedThroughputExceededException . If at least one of
the items is successfully processed, then BatchGetItem
completes successfully, while returning the keys of the unread
items in UnprocessedKeys .
If DynamoDB returns any unprocessed items, you should retry
the batch operation on those items. However, we strongly
recommend that you use an exponential backoff algorithm . If
you retry the batch operation immediately, the underlying read
or write requests can still fail due to throttling on the
individual tables. If you delay the batch operation using
exponential backoff, the individual requests in the batch are
much more likely to succeed.
For more information, go to `Batch Operations and Error
Handling`_ in the Amazon DynamoDB Developer Guide .
By default, BatchGetItem performs eventually consistent reads
on every table in the request. If you want strongly consistent
reads instead, you can set ConsistentRead to `True` for any or
all tables.
In order to minimize response latency, BatchGetItem retrieves
items in parallel.
When designing your application, keep in mind that DynamoDB
does not return attributes in any particular order. To help
parse the response by item, include the primary key values for
the items in your request in the AttributesToGet parameter.
If a requested item does not exist, it is not returned in the
result. Requests for nonexistent items consume the minimum
read capacity units according to the type of read. For more
information, see `Capacity Units Calculations`_ in the Amazon
DynamoDB Developer Guide .
:type request_items: map
:param request_items:
A map of one or more table names and, for each table, the corresponding
primary keys for the items to retrieve. Each table name can be
invoked only once.
Each element in the map consists of the following:
+ Keys - An array of primary key attribute values that define specific
items in the table. For each primary key, you must provide all of
the key attributes. For example, with a hash type primary key, you
only need to specify the hash attribute. For a hash-and-range type
primary key, you must specify both the hash attribute and the range
attribute.
+ AttributesToGet - One or more attributes to be retrieved from the
table. By default, all attributes are returned. If a specified
attribute is not found, it does not appear in the result. Note that
AttributesToGet has no effect on provisioned throughput
consumption. DynamoDB determines capacity units consumed based on
item size, not on the amount of data that is returned to an
application.
+ ConsistentRead - If `True`, a strongly consistent read is used; if
`False` (the default), an eventually consistent read is used.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
"""
params = {'RequestItems': request_items, }
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
return self.make_request(action='BatchGetItem',
body=json.dumps(params))
def batch_write_item(self, request_items, return_consumed_capacity=None,
return_item_collection_metrics=None):
"""
The BatchWriteItem operation puts or deletes multiple items in
one or more tables. A single call to BatchWriteItem can write
up to 16 MB of data, which can comprise as many as 25 put or
delete requests. Individual items to be written can be as
large as 400 KB.
BatchWriteItem cannot update items. To update items, use the
UpdateItem API.
The individual PutItem and DeleteItem operations specified in
BatchWriteItem are atomic; however BatchWriteItem as a whole
is not. If any requested operations fail because the table's
provisioned throughput is exceeded or an internal processing
failure occurs, the failed operations are returned in the
UnprocessedItems response parameter. You can investigate and
optionally resend the requests. Typically, you would call
BatchWriteItem in a loop. Each iteration would check for
unprocessed items and submit a new BatchWriteItem request with
those unprocessed items until all items have been processed.
Note that if none of the items can be processed due to
insufficient provisioned throughput on all of the tables in
the request, then BatchWriteItem will return a
ProvisionedThroughputExceededException .
If DynamoDB returns any unprocessed items, you should retry
the batch operation on those items. However, we strongly
recommend that you use an exponential backoff algorithm . If
you retry the batch operation immediately, the underlying read
or write requests can still fail due to throttling on the
individual tables. If you delay the batch operation using
exponential backoff, the individual requests in the batch are
much more likely to succeed.
For more information, go to `Batch Operations and Error
Handling`_ in the Amazon DynamoDB Developer Guide .
With BatchWriteItem , you can efficiently write or delete
large amounts of data, such as from Amazon Elastic MapReduce
(EMR), or copy data from another database into DynamoDB. In
order to improve performance with these large-scale
operations, BatchWriteItem does not behave in the same way as
individual PutItem and DeleteItem calls would For example, you
cannot specify conditions on individual put and delete
requests, and BatchWriteItem does not return deleted items in
the response.
If you use a programming language that supports concurrency,
such as Java, you can use threads to write items in parallel.
Your application must include the necessary logic to manage
the threads. With languages that don't support threading, such
as PHP, you must update or delete the specified items one at a
time. In both situations, BatchWriteItem provides an
alternative where the API performs the specified put and
delete operations in parallel, giving you the power of the
thread pool approach without having to introduce complexity
into your application.
Parallel processing reduces latency, but each specified put
and delete request consumes the same number of write capacity
units whether it is processed in parallel or not. Delete
operations on nonexistent items consume one write capacity
unit.
If one or more of the following is true, DynamoDB rejects the
entire batch write operation:
+ One or more tables specified in the BatchWriteItem request
does not exist.
+ Primary key attributes specified on an item in the request
do not match those in the corresponding table's primary key
schema.
+ You try to perform multiple operations on the same item in
the same BatchWriteItem request. For example, you cannot put
and delete the same item in the same BatchWriteItem request.
+ There are more than 25 requests in the batch.
+ Any individual item in a batch exceeds 400 KB.
+ The total request size exceeds 16 MB.
:type request_items: map
:param request_items:
A map of one or more table names and, for each table, a list of
operations to be performed ( DeleteRequest or PutRequest ). Each
element in the map consists of the following:
+ DeleteRequest - Perform a DeleteItem operation on the specified item.
The item to be deleted is identified by a Key subelement:
+ Key - A map of primary key attribute values that uniquely identify
the ! item. Each entry in this map consists of an attribute name
and an attribute value. For each primary key, you must provide all
of the key attributes. For example, with a hash type primary key,
you only need to specify the hash attribute. For a hash-and-range
type primary key, you must specify both the hash attribute and the
range attribute.
+ PutRequest - Perform a PutItem operation on the specified item. The
item to be put is identified by an Item subelement:
+ Item - A map of attributes and their values. Each entry in this map
consists of an attribute name and an attribute value. Attribute
values must not be null; string and binary type attributes must
have lengths greater than zero; and set type attributes must not be
empty. Requests that contain empty values will be rejected with a
ValidationException exception. If you specify any attributes that
are part of an index key, then the data types for those attributes
must match those of the schema in the table's attribute definition.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type return_item_collection_metrics: string
:param return_item_collection_metrics: A value that if set to `SIZE`,
the response includes statistics about item collections, if any,
that were modified during the operation are returned in the
response. If set to `NONE` (the default), no statistics are
returned.
"""
params = {'RequestItems': request_items, }
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if return_item_collection_metrics is not None:
params['ReturnItemCollectionMetrics'] = return_item_collection_metrics
return self.make_request(action='BatchWriteItem',
body=json.dumps(params))
def create_table(self, attribute_definitions, table_name, key_schema,
provisioned_throughput, local_secondary_indexes=None,
global_secondary_indexes=None):
"""
The CreateTable operation adds a new table to your account. In
an AWS account, table names must be unique within each region.
That is, you can have two tables with same name if you create
the tables in different regions.
CreateTable is an asynchronous operation. Upon receiving a
CreateTable request, DynamoDB immediately returns a response
with a TableStatus of `CREATING`. After the table is created,
DynamoDB sets the TableStatus to `ACTIVE`. You can perform
read and write operations only on an `ACTIVE` table.
You can optionally define secondary indexes on the new table,
as part of the CreateTable operation. If you want to create
multiple tables with secondary indexes on them, you must
create the tables sequentially. Only one table with secondary
indexes can be in the `CREATING` state at any given time.
You can use the DescribeTable API to check the table status.
:type attribute_definitions: list
:param attribute_definitions: An array of attributes that describe the
key schema for the table and indexes.
:type table_name: string
:param table_name: The name of the table to create.
:type key_schema: list
:param key_schema: Specifies the attributes that make up the primary
key for a table or an index. The attributes in KeySchema must also
be defined in the AttributeDefinitions array. For more information,
see `Data Model`_ in the Amazon DynamoDB Developer Guide .
Each KeySchemaElement in the array is composed of:
+ AttributeName - The name of this key attribute.
+ KeyType - Determines whether the key attribute is `HASH` or `RANGE`.
For a primary key that consists of a hash attribute, you must specify
exactly one element with a KeyType of `HASH`.
For a primary key that consists of hash and range attributes, you must
specify exactly two elements, in this order: The first element must
have a KeyType of `HASH`, and the second element must have a
KeyType of `RANGE`.
For more information, see `Specifying the Primary Key`_ in the Amazon
DynamoDB Developer Guide .
:type local_secondary_indexes: list
:param local_secondary_indexes:
One or more local secondary indexes (the maximum is five) to be created
on the table. Each index is scoped to a given hash key value. There
is a 10 GB size limit per hash key; otherwise, the size of a local
secondary index is unconstrained.
Each local secondary index in the array includes the following:
+ IndexName - The name of the local secondary index. Must be unique
only for this table.
+ KeySchema - Specifies the key schema for the local secondary index.
The key schema must begin with the same hash key attribute as the
table.
+ Projection - Specifies attributes that are copied (projected) from
the table into the index. These are in addition to the primary key
attributes and index key attributes, which are automatically
projected. Each attribute specification is composed of:
+ ProjectionType - One of the following:
+ `KEYS_ONLY` - Only the index and primary keys are projected into the
index.
+ `INCLUDE` - Only the specified table attributes are projected into
the index. The list of projected attributes are in NonKeyAttributes
.
+ `ALL` - All of the table attributes are projected into the index.
+ NonKeyAttributes - A list of one or more non-key attribute names that
are projected into the secondary index. The total count of
attributes specified in NonKeyAttributes , summed across all of the
secondary indexes, must not exceed 20. If you project the same
attribute into two different indexes, this counts as two distinct
attributes when determining the total.
:type global_secondary_indexes: list
:param global_secondary_indexes:
One or more global secondary indexes (the maximum is five) to be
created on the table. Each global secondary index in the array
includes the following:
+ IndexName - The name of the global secondary index. Must be unique
only for this table.
+ KeySchema - Specifies the key schema for the global secondary index.
+ Projection - Specifies attributes that are copied (projected) from
the table into the index. These are in addition to the primary key
attributes and index key attributes, which are automatically
projected. Each attribute specification is composed of:
+ ProjectionType - One of the following:
+ `KEYS_ONLY` - Only the index and primary keys are projected into the
index.
+ `INCLUDE` - Only the specified table attributes are projected into
the index. The list of projected attributes are in NonKeyAttributes
.
+ `ALL` - All of the table attributes are projected into the index.
+ NonKeyAttributes - A list of one or more non-key attribute names that
are projected into the secondary index. The total count of
attributes specified in NonKeyAttributes , summed across all of the
secondary indexes, must not exceed 20. If you project the same
attribute into two different indexes, this counts as two distinct
attributes when determining the total.
+ ProvisionedThroughput - The provisioned throughput settings for the
global secondary index, consisting of read and write capacity
units.
:type provisioned_throughput: dict
:param provisioned_throughput: Represents the provisioned throughput
settings for a specified table or index. The settings can be
modified using the UpdateTable operation.
For current minimum and maximum provisioned throughput values, see
`Limits`_ in the Amazon DynamoDB Developer Guide .
"""
params = {
'AttributeDefinitions': attribute_definitions,
'TableName': table_name,
'KeySchema': key_schema,
'ProvisionedThroughput': provisioned_throughput,
}
if local_secondary_indexes is not None:
params['LocalSecondaryIndexes'] = local_secondary_indexes
if global_secondary_indexes is not None:
params['GlobalSecondaryIndexes'] = global_secondary_indexes
return self.make_request(action='CreateTable',
body=json.dumps(params))
def delete_item(self, table_name, key, expected=None,
conditional_operator=None, return_values=None,
return_consumed_capacity=None,
return_item_collection_metrics=None,
condition_expression=None,
expression_attribute_names=None,
expression_attribute_values=None):
"""
Deletes a single item in a table by primary key. You can
perform a conditional delete operation that deletes the item
if it exists, or if it has an expected attribute value.
In addition to deleting an item, you can also return the
item's attribute values in the same operation, using the
ReturnValues parameter.
Unless you specify conditions, the DeleteItem is an idempotent
operation; running it multiple times on the same item or
attribute does not result in an error response.
Conditional deletes are useful for deleting items only if
specific conditions are met. If those conditions are met,
DynamoDB performs the delete. Otherwise, the item is not
deleted.
:type table_name: string
:param table_name: The name of the table from which to delete the item.
:type key: map
:param key: A map of attribute names to AttributeValue objects,
representing the primary key of the item to delete.
For the primary key, you must provide all of the attributes. For
example, with a hash type primary key, you only need to specify the
hash attribute. For a hash-and-range type primary key, you must
specify both the hash attribute and the range attribute.
:type expected: map
:param expected:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use Expected and ConditionExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A map of attribute/condition pairs. Expected provides a conditional
block for the DeleteItem operation.
Each element of Expected consists of an attribute name, a comparison
operator, and one or more values. DynamoDB compares the attribute
with the value(s) you supplied, using the comparison operator. For
each Expected element, the result of the evaluation is either true
or false.
If you specify more than one element in the Expected map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
If the Expected map evaluates to true, then the conditional operation
succeeds; otherwise, it fails.
Expected contains the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
ComparisonOperator being used. For type Number, value comparisons
are numeric. String value comparisons for greater than, equals, or
less than are based on ASCII character code values. For example,
`a` is greater than `A`, and `a` is greater than `B`. For a list of
code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For type Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions.
+ ComparisonOperator - A comparator for evaluating attributes in the
AttributeValueList . When performing the comparison, DynamoDB uses
strongly consistent reads. The following comparison operators are
available: `EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL |
CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN | BETWEEN` The following
are descriptions of each comparison operator.
+ `EQ` : Equal. `EQ` is supported for all datatypes, including lists
and maps. AttributeValueList can contain only one AttributeValue
element of type String, Number, Binary, String Set, Number Set, or
Binary Set. If an item contains an AttributeValue element of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `NE` : Not equal. `NE` is supported for all datatypes, including
lists and maps. AttributeValueList can contain only one
AttributeValue of type String, Number, Binary, String Set, Number
Set, or Binary Set. If an item contains an AttributeValue of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `LE` : Less than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `LT` : Less than. AttributeValueList can contain only one
AttributeValue of type String, Number, or Binary (not a set type).
If an item contains an AttributeValue element of a different type
than the one specified in the request, the value does not match.
For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GE` : Greater than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GT` : Greater than. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `NOT_NULL` : The attribute exists. `NOT_NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
existence of an attribute, not its data type. If the data type of
attribute " `a`" is null, and you evaluate it using `NOT_NULL`, the
result is a Boolean true . This result is because the attribute "
`a`" exists; its data type is not relevant to the `NOT_NULL`
comparison operator.
+ `NULL` : The attribute does not exist. `NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
nonexistence of an attribute, not its data type. If the data type
of attribute " `a`" is null, and you evaluate it using `NULL`, the
result is a Boolean false . This is because the attribute " `a`"
exists; its data type is not relevant to the `NULL` comparison
operator.
+ `CONTAINS` : Checks for a subsequence, or value in a set.
AttributeValueList can contain only one AttributeValue element of
type String, Number, or Binary (not a set type). If the target
attribute of the comparison is of type String, then the operator
checks for a substring match. If the target attribute of the
comparison is of type Binary, then the operator looks for a
subsequence of the target that matches the input. If the target
attribute of the comparison is a set (" `SS`", " `NS`", or "
`BS`"), then the operator evaluates to true if it finds an exact
match with any member of the set. CONTAINS is supported for lists:
When evaluating " `a CONTAINS b`", " `a`" can be a list; however, "
`b`" cannot be a set, a map, or a list.
+ `NOT_CONTAINS` : Checks for absence of a subsequence, or absence of a
value in a set. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If the target attribute of the comparison is a String, then
the operator checks for the absence of a substring match. If the
target attribute of the comparison is Binary, then the operator
checks for the absence of a subsequence of the target that matches
the input. If the target attribute of the comparison is a set ("
`SS`", " `NS`", or " `BS`"), then the operator evaluates to true if
it does not find an exact match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating " `a NOT
CONTAINS b`", " `a`" can be a list; however, " `b`" cannot be a
set, a map, or a list.
+ `BEGINS_WITH` : Checks for a prefix. AttributeValueList can contain
only one AttributeValue of type String or Binary (not a Number or a
set type). The target attribute of the comparison must be of type
String or Binary (not a Number or a set type). > <li>
+ `IN` : Checks for matching elements within two sets.
AttributeValueList can contain one or more AttributeValue elements
of type String, Number, or Binary (not a set type). These
attributes are compared against an existing set type attribute of
an item. If any elements of the input set are present in the item
attribute, the expression evaluates to true.
+ `BETWEEN` : Greater than or equal to the first value, and less than
or equal to the second value. AttributeValueList must contain two
AttributeValue elements of the same type, either String, Number, or
Binary (not a set type). A target attribute matches if the target
value is greater than, or equal to, the first element and less
than, or equal to, the second element. If an item contains an
AttributeValue element of a different type than the one specified
in the request, the value does not match. For example, `{"S":"6"}`
does not compare to `{"N":"6"}`. Also, `{"N":"6"}` does not compare
to `{"NS":["6", "2", "1"]}`
For usage examples of AttributeValueList and ComparisonOperator , see
`Legacy Conditional Parameters`_ in the Amazon DynamoDB Developer
Guide .
For backward compatibility with previous DynamoDB releases, the
following parameters can be used instead of AttributeValueList and
ComparisonOperator :
+ Value - A value for DynamoDB to compare with an attribute.
+ Exists - A Boolean value that causes DynamoDB to evaluate the value
before attempting the conditional operation:
+ If Exists is `True`, DynamoDB will check to see if that attribute
value already exists in the table. If it is found, then the
condition evaluates to true; otherwise the condition evaluate to
false.
+ If Exists is `False`, DynamoDB assumes that the attribute value does
not exist in the table. If in fact the value does not exist, then
the assumption is valid and the condition evaluates to true. If the
value is found, despite the assumption that it does not exist, the
condition evaluates to false.
Note that the default value for Exists is `True`.
The Value and Exists parameters are incompatible with
AttributeValueList and ComparisonOperator . Note that if you use
both sets of parameters at once, DynamoDB will return a
ValidationException exception.
:type conditional_operator: string
:param conditional_operator:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use ConditionalOperator and ConditionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the Expected map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type return_values: string
:param return_values:
Use ReturnValues if you want to get the item attributes as they
appeared before they were deleted. For DeleteItem , the valid
values are:
+ `NONE` - If ReturnValues is not specified, or if its value is `NONE`,
then nothing is returned. (This setting is the default for
ReturnValues .)
+ `ALL_OLD` - The content of the old item is returned.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type return_item_collection_metrics: string
:param return_item_collection_metrics: A value that if set to `SIZE`,
the response includes statistics about item collections, if any,
that were modified during the operation are returned in the
response. If set to `NONE` (the default), no statistics are
returned.
:type condition_expression: string
:param condition_expression: A condition that must be satisfied in
order for a conditional DeleteItem to succeed.
An expression can contain any of the following:
+ Boolean functions: `attribute_exists | attribute_not_exists |
contains | begins_with` These function names are case-sensitive.
+ Comparison operators: ` = | <> | < | > | <=
| >= | BETWEEN | IN`
+ Logical operators: `AND | OR | NOT`
For more information on condition expressions, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
"""
params = {'TableName': table_name, 'Key': key, }
if expected is not None:
params['Expected'] = expected
if conditional_operator is not None:
params['ConditionalOperator'] = conditional_operator
if return_values is not None:
params['ReturnValues'] = return_values
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if return_item_collection_metrics is not None:
params['ReturnItemCollectionMetrics'] = return_item_collection_metrics
if condition_expression is not None:
params['ConditionExpression'] = condition_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
if expression_attribute_values is not None:
params['ExpressionAttributeValues'] = expression_attribute_values
return self.make_request(action='DeleteItem',
body=json.dumps(params))
def delete_table(self, table_name):
"""
The DeleteTable operation deletes a table and all of its
items. After a DeleteTable request, the specified table is in
the `DELETING` state until DynamoDB completes the deletion. If
the table is in the `ACTIVE` state, you can delete it. If a
table is in `CREATING` or `UPDATING` states, then DynamoDB
returns a ResourceInUseException . If the specified table does
not exist, DynamoDB returns a ResourceNotFoundException . If
table is already in the `DELETING` state, no error is
returned.
DynamoDB might continue to accept data read and write
operations, such as GetItem and PutItem , on a table in the
`DELETING` state until the table deletion is complete.
When you delete a table, any indexes on that table are also
deleted.
Use the DescribeTable API to check the status of the table.
:type table_name: string
:param table_name: The name of the table to delete.
"""
params = {'TableName': table_name, }
return self.make_request(action='DeleteTable',
body=json.dumps(params))
def describe_table(self, table_name):
"""
Returns information about the table, including the current
status of the table, when it was created, the primary key
schema, and any indexes on the table.
If you issue a DescribeTable request immediately after a
CreateTable request, DynamoDB might return a
ResourceNotFoundException. This is because DescribeTable uses
an eventually consistent query, and the metadata for your
table might not be available at that moment. Wait for a few
seconds, and then try the DescribeTable request again.
:type table_name: string
:param table_name: The name of the table to describe.
"""
params = {'TableName': table_name, }
return self.make_request(action='DescribeTable',
body=json.dumps(params))
def get_item(self, table_name, key, attributes_to_get=None,
consistent_read=None, return_consumed_capacity=None,
projection_expression=None, expression_attribute_names=None):
"""
The GetItem operation returns a set of attributes for the item
with the given primary key. If there is no matching item,
GetItem does not return any data.
GetItem provides an eventually consistent read by default. If
your application requires a strongly consistent read, set
ConsistentRead to `True`. Although a strongly consistent read
might take more time than an eventually consistent read, it
always returns the last updated value.
:type table_name: string
:param table_name: The name of the table containing the requested item.
:type key: map
:param key: A map of attribute names to AttributeValue objects,
representing the primary key of the item to retrieve.
For the primary key, you must provide all of the attributes. For
example, with a hash type primary key, you only need to specify the
hash attribute. For a hash-and-range type primary key, you must
specify both the hash attribute and the range attribute.
:type attributes_to_get: list
:param attributes_to_get:
There is a newer parameter available. Use ProjectionExpression instead.
Note that if you use AttributesToGet and ProjectionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter allows you to retrieve lists or maps; however, it cannot
retrieve individual list or map elements.
The names of one or more attributes to retrieve. If no attribute names
are specified, then all attributes will be returned. If any of the
requested attributes are not found, they will not appear in the
result.
Note that AttributesToGet has no effect on provisioned throughput
consumption. DynamoDB determines capacity units consumed based on
item size, not on the amount of data that is returned to an
application.
:type consistent_read: boolean
:param consistent_read: A value that if set to `True`, then the
operation uses strongly consistent reads; otherwise, eventually
consistent reads are used.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type projection_expression: string
:param projection_expression: A string that identifies one or more
attributes to retrieve from the table. These attributes can include
scalars, sets, or elements of a JSON document. The attributes in
the expression must be separated by commas.
If no attribute names are specified, then all attributes will be
returned. If any of the requested attributes are not found, they
will not appear in the result.
For more information on projection expressions, go to `Accessing Item
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
"""
params = {'TableName': table_name, 'Key': key, }
if attributes_to_get is not None:
params['AttributesToGet'] = attributes_to_get
if consistent_read is not None:
params['ConsistentRead'] = consistent_read
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if projection_expression is not None:
params['ProjectionExpression'] = projection_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
return self.make_request(action='GetItem',
body=json.dumps(params))
def list_tables(self, exclusive_start_table_name=None, limit=None):
"""
Returns an array of table names associated with the current
account and endpoint. The output from ListTables is paginated,
with each page returning a maximum of 100 table names.
:type exclusive_start_table_name: string
:param exclusive_start_table_name: The first table name that this
operation will evaluate. Use the value that was returned for
LastEvaluatedTableName in a previous operation, so that you can
obtain the next page of results.
:type limit: integer
:param limit: A maximum number of table names to return. If this
parameter is not specified, the limit is 100.
"""
params = {}
if exclusive_start_table_name is not None:
params['ExclusiveStartTableName'] = exclusive_start_table_name
if limit is not None:
params['Limit'] = limit
return self.make_request(action='ListTables',
body=json.dumps(params))
def put_item(self, table_name, item, expected=None, return_values=None,
return_consumed_capacity=None,
return_item_collection_metrics=None,
conditional_operator=None, condition_expression=None,
expression_attribute_names=None,
expression_attribute_values=None):
"""
Creates a new item, or replaces an old item with a new item.
If an item that has the same primary key as the new item
already exists in the specified table, the new item completely
replaces the existing item. You can perform a conditional put
operation (add a new item if one with the specified primary
key doesn't exist), or replace an existing item if it has
certain attribute values.
In addition to putting an item, you can also return the item's
attribute values in the same operation, using the ReturnValues
parameter.
When you add an item, the primary key attribute(s) are the
only required attributes. Attribute values cannot be null.
String and Binary type attributes must have lengths greater
than zero. Set type attributes cannot be empty. Requests with
empty values will be rejected with a ValidationException
exception.
You can request that PutItem return either a copy of the
original item (before the update) or a copy of the updated
item (after the update). For more information, see the
ReturnValues description below.
To prevent a new item from replacing an existing item, use a
conditional put operation with ComparisonOperator set to
`NULL` for the primary key attribute, or attributes.
For more information about using this API, see `Working with
Items`_ in the Amazon DynamoDB Developer Guide .
:type table_name: string
:param table_name: The name of the table to contain the item.
:type item: map
:param item: A map of attribute name/value pairs, one for each
attribute. Only the primary key attributes are required; you can
optionally provide other attribute name-value pairs for the item.
You must provide all of the attributes for the primary key. For
example, with a hash type primary key, you only need to specify the
hash attribute. For a hash-and-range type primary key, you must
specify both the hash attribute and the range attribute.
If you specify any attributes that are part of an index key, then the
data types for those attributes must match those of the schema in
the table's attribute definition.
For more information about primary keys, see `Primary Key`_ in the
Amazon DynamoDB Developer Guide .
Each element in the Item map is an AttributeValue object.
:type expected: map
:param expected:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use Expected and ConditionExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A map of attribute/condition pairs. Expected provides a conditional
block for the PutItem operation.
Each element of Expected consists of an attribute name, a comparison
operator, and one or more values. DynamoDB compares the attribute
with the value(s) you supplied, using the comparison operator. For
each Expected element, the result of the evaluation is either true
or false.
If you specify more than one element in the Expected map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
If the Expected map evaluates to true, then the conditional operation
succeeds; otherwise, it fails.
Expected contains the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
ComparisonOperator being used. For type Number, value comparisons
are numeric. String value comparisons for greater than, equals, or
less than are based on ASCII character code values. For example,
`a` is greater than `A`, and `a` is greater than `B`. For a list of
code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For type Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions.
+ ComparisonOperator - A comparator for evaluating attributes in the
AttributeValueList . When performing the comparison, DynamoDB uses
strongly consistent reads. The following comparison operators are
available: `EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL |
CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN | BETWEEN` The following
are descriptions of each comparison operator.
+ `EQ` : Equal. `EQ` is supported for all datatypes, including lists
and maps. AttributeValueList can contain only one AttributeValue
element of type String, Number, Binary, String Set, Number Set, or
Binary Set. If an item contains an AttributeValue element of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `NE` : Not equal. `NE` is supported for all datatypes, including
lists and maps. AttributeValueList can contain only one
AttributeValue of type String, Number, Binary, String Set, Number
Set, or Binary Set. If an item contains an AttributeValue of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `LE` : Less than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `LT` : Less than. AttributeValueList can contain only one
AttributeValue of type String, Number, or Binary (not a set type).
If an item contains an AttributeValue element of a different type
than the one specified in the request, the value does not match.
For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GE` : Greater than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GT` : Greater than. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `NOT_NULL` : The attribute exists. `NOT_NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
existence of an attribute, not its data type. If the data type of
attribute " `a`" is null, and you evaluate it using `NOT_NULL`, the
result is a Boolean true . This result is because the attribute "
`a`" exists; its data type is not relevant to the `NOT_NULL`
comparison operator.
+ `NULL` : The attribute does not exist. `NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
nonexistence of an attribute, not its data type. If the data type
of attribute " `a`" is null, and you evaluate it using `NULL`, the
result is a Boolean false . This is because the attribute " `a`"
exists; its data type is not relevant to the `NULL` comparison
operator.
+ `CONTAINS` : Checks for a subsequence, or value in a set.
AttributeValueList can contain only one AttributeValue element of
type String, Number, or Binary (not a set type). If the target
attribute of the comparison is of type String, then the operator
checks for a substring match. If the target attribute of the
comparison is of type Binary, then the operator looks for a
subsequence of the target that matches the input. If the target
attribute of the comparison is a set (" `SS`", " `NS`", or "
`BS`"), then the operator evaluates to true if it finds an exact
match with any member of the set. CONTAINS is supported for lists:
When evaluating " `a CONTAINS b`", " `a`" can be a list; however, "
`b`" cannot be a set, a map, or a list.
+ `NOT_CONTAINS` : Checks for absence of a subsequence, or absence of a
value in a set. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If the target attribute of the comparison is a String, then
the operator checks for the absence of a substring match. If the
target attribute of the comparison is Binary, then the operator
checks for the absence of a subsequence of the target that matches
the input. If the target attribute of the comparison is a set ("
`SS`", " `NS`", or " `BS`"), then the operator evaluates to true if
it does not find an exact match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating " `a NOT
CONTAINS b`", " `a`" can be a list; however, " `b`" cannot be a
set, a map, or a list.
+ `BEGINS_WITH` : Checks for a prefix. AttributeValueList can contain
only one AttributeValue of type String or Binary (not a Number or a
set type). The target attribute of the comparison must be of type
String or Binary (not a Number or a set type). > <li>
+ `IN` : Checks for matching elements within two sets.
AttributeValueList can contain one or more AttributeValue elements
of type String, Number, or Binary (not a set type). These
attributes are compared against an existing set type attribute of
an item. If any elements of the input set are present in the item
attribute, the expression evaluates to true.
+ `BETWEEN` : Greater than or equal to the first value, and less than
or equal to the second value. AttributeValueList must contain two
AttributeValue elements of the same type, either String, Number, or
Binary (not a set type). A target attribute matches if the target
value is greater than, or equal to, the first element and less
than, or equal to, the second element. If an item contains an
AttributeValue element of a different type than the one specified
in the request, the value does not match. For example, `{"S":"6"}`
does not compare to `{"N":"6"}`. Also, `{"N":"6"}` does not compare
to `{"NS":["6", "2", "1"]}`
For usage examples of AttributeValueList and ComparisonOperator , see
`Legacy Conditional Parameters`_ in the Amazon DynamoDB Developer
Guide .
For backward compatibility with previous DynamoDB releases, the
following parameters can be used instead of AttributeValueList and
ComparisonOperator :
+ Value - A value for DynamoDB to compare with an attribute.
+ Exists - A Boolean value that causes DynamoDB to evaluate the value
before attempting the conditional operation:
+ If Exists is `True`, DynamoDB will check to see if that attribute
value already exists in the table. If it is found, then the
condition evaluates to true; otherwise the condition evaluate to
false.
+ If Exists is `False`, DynamoDB assumes that the attribute value does
not exist in the table. If in fact the value does not exist, then
the assumption is valid and the condition evaluates to true. If the
value is found, despite the assumption that it does not exist, the
condition evaluates to false.
Note that the default value for Exists is `True`.
The Value and Exists parameters are incompatible with
AttributeValueList and ComparisonOperator . Note that if you use
both sets of parameters at once, DynamoDB will return a
ValidationException exception.
:type return_values: string
:param return_values:
Use ReturnValues if you want to get the item attributes as they
appeared before they were updated with the PutItem request. For
PutItem , the valid values are:
+ `NONE` - If ReturnValues is not specified, or if its value is `NONE`,
then nothing is returned. (This setting is the default for
ReturnValues .)
+ `ALL_OLD` - If PutItem overwrote an attribute name-value pair, then
the content of the old item is returned.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type return_item_collection_metrics: string
:param return_item_collection_metrics: A value that if set to `SIZE`,
the response includes statistics about item collections, if any,
that were modified during the operation are returned in the
response. If set to `NONE` (the default), no statistics are
returned.
:type conditional_operator: string
:param conditional_operator:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use ConditionalOperator and ConditionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the Expected map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type condition_expression: string
:param condition_expression: A condition that must be satisfied in
order for a conditional PutItem operation to succeed.
An expression can contain any of the following:
+ Boolean functions: `attribute_exists | attribute_not_exists |
contains | begins_with` These function names are case-sensitive.
+ Comparison operators: ` = | <> | < | > | <=
| >= | BETWEEN | IN`
+ Logical operators: `AND | OR | NOT`
For more information on condition expressions, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
"""
params = {'TableName': table_name, 'Item': item, }
if expected is not None:
params['Expected'] = expected
if return_values is not None:
params['ReturnValues'] = return_values
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if return_item_collection_metrics is not None:
params['ReturnItemCollectionMetrics'] = return_item_collection_metrics
if conditional_operator is not None:
params['ConditionalOperator'] = conditional_operator
if condition_expression is not None:
params['ConditionExpression'] = condition_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
if expression_attribute_values is not None:
params['ExpressionAttributeValues'] = expression_attribute_values
return self.make_request(action='PutItem',
body=json.dumps(params))
def query(self, table_name, key_conditions, index_name=None, select=None,
attributes_to_get=None, limit=None, consistent_read=None,
query_filter=None, conditional_operator=None,
scan_index_forward=None, exclusive_start_key=None,
return_consumed_capacity=None, projection_expression=None,
filter_expression=None, expression_attribute_names=None,
expression_attribute_values=None):
"""
A Query operation directly accesses items from a table using
the table primary key, or from an index using the index key.
You must provide a specific hash key value. You can narrow the
scope of the query by using comparison operators on the range
key value, or on the index key. You can use the
ScanIndexForward parameter to get results in forward or
reverse order, by range key or by index key.
Queries that do not return results consume the minimum number
of read capacity units for that type of read operation.
If the total number of items meeting the query criteria
exceeds the result set size limit of 1 MB, the query stops and
results are returned to the user with LastEvaluatedKey to
continue the query in a subsequent operation. Unlike a Scan
operation, a Query operation never returns both an empty
result set and a LastEvaluatedKey . The LastEvaluatedKey is
only provided if the results exceed 1 MB, or if you have used
Limit .
You can query a table, a local secondary index, or a global
secondary index. For a query on a table or on a local
secondary index, you can set ConsistentRead to true and obtain
a strongly consistent result. Global secondary indexes support
eventually consistent reads only, so do not specify
ConsistentRead when querying a global secondary index.
:type table_name: string
:param table_name: The name of the table containing the requested
items.
:type index_name: string
:param index_name: The name of an index to query. This index can be any
local secondary index or global secondary index on the table.
:type select: string
:param select: The attributes to be returned in the result. You can
retrieve all item attributes, specific item attributes, the count
of matching items, or in the case of an index, some or all of the
attributes projected into the index.
+ `ALL_ATTRIBUTES` - Returns all of the item attributes from the
specified table or index. If you query a local secondary index,
then for each matching item in the index DynamoDB will fetch the
entire item from the parent table. If the index is configured to
project all item attributes, then all of the data can be obtained
from the local secondary index, and no fetching is required.
+ `ALL_PROJECTED_ATTRIBUTES` - Allowed only when querying an index.
Retrieves all attributes that have been projected into the index.
If the index is configured to project all attributes, this return
value is equivalent to specifying `ALL_ATTRIBUTES`.
+ `COUNT` - Returns the number of matching items, rather than the
matching items themselves.
+ `SPECIFIC_ATTRIBUTES` - Returns only the attributes listed in
AttributesToGet . This return value is equivalent to specifying
AttributesToGet without specifying any value for Select . If you
query a local secondary index and request only attributes that are
projected into that index, the operation will read only the index
and not the table. If any of the requested attributes are not
projected into the local secondary index, DynamoDB will fetch each
of these attributes from the parent table. This extra fetching
incurs additional throughput cost and latency. If you query a
global secondary index, you can only request attributes that are
projected into the index. Global secondary index queries cannot
fetch attributes from the parent table.
If neither Select nor AttributesToGet are specified, DynamoDB defaults
to `ALL_ATTRIBUTES` when accessing a table, and
`ALL_PROJECTED_ATTRIBUTES` when accessing an index. You cannot use
both Select and AttributesToGet together in a single request,
unless the value for Select is `SPECIFIC_ATTRIBUTES`. (This usage
is equivalent to specifying AttributesToGet without any value for
Select .)
:type attributes_to_get: list
:param attributes_to_get:
There is a newer parameter available. Use ProjectionExpression instead.
Note that if you use AttributesToGet and ProjectionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter allows you to retrieve lists or maps; however, it cannot
retrieve individual list or map elements.
The names of one or more attributes to retrieve. If no attribute names
are specified, then all attributes will be returned. If any of the
requested attributes are not found, they will not appear in the
result.
Note that AttributesToGet has no effect on provisioned throughput
consumption. DynamoDB determines capacity units consumed based on
item size, not on the amount of data that is returned to an
application.
You cannot use both AttributesToGet and Select together in a Query
request, unless the value for Select is `SPECIFIC_ATTRIBUTES`.
(This usage is equivalent to specifying AttributesToGet without any
value for Select .)
If you query a local secondary index and request only attributes that
are projected into that index, the operation will read only the
index and not the table. If any of the requested attributes are not
projected into the local secondary index, DynamoDB will fetch each
of these attributes from the parent table. This extra fetching
incurs additional throughput cost and latency.
If you query a global secondary index, you can only request attributes
that are projected into the index. Global secondary index queries
cannot fetch attributes from the parent table.
:type limit: integer
:param limit: The maximum number of items to evaluate (not necessarily
the number of matching items). If DynamoDB processes the number of
items up to the limit while processing the results, it stops the
operation and returns the matching values up to that point, and a
key in LastEvaluatedKey to apply in a subsequent operation, so that
you can pick up where you left off. Also, if the processed data set
size exceeds 1 MB before DynamoDB reaches this limit, it stops the
operation and returns the matching values up to the limit, and a
key in LastEvaluatedKey to apply in a subsequent operation to
continue the operation. For more information, see `Query and Scan`_
in the Amazon DynamoDB Developer Guide .
:type consistent_read: boolean
:param consistent_read: A value that if set to `True`, then the
operation uses strongly consistent reads; otherwise, eventually
consistent reads are used.
Strongly consistent reads are not supported on global secondary
indexes. If you query a global secondary index with ConsistentRead
set to `True`, you will receive an error message.
:type key_conditions: map
:param key_conditions: The selection criteria for the query. For a
query on a table, you can have conditions only on the table primary
key attributes. You must specify the hash key attribute name and
value as an `EQ` condition. You can optionally specify a second
condition, referring to the range key attribute. If you do not
specify a range key condition, all items under the hash key will be
fetched and processed. Any filters will applied after this.
For a query on an index, you can have conditions only on the index key
attributes. You must specify the index hash attribute name and
value as an EQ condition. You can optionally specify a second
condition, referring to the index key range attribute.
Each KeyConditions element consists of an attribute name to compare,
along with the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
ComparisonOperator being used. For type Number, value comparisons
are numeric. String value comparisons for greater than, equals, or
less than are based on ASCII character code values. For example,
`a` is greater than `A`, and `a` is greater than `B`. For a list of
code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions.
+ ComparisonOperator - A comparator for evaluating attributes, for
example, equals, greater than, less than, and so on. For
KeyConditions , only the following comparison operators are
supported: `EQ | LE | LT | GE | GT | BEGINS_WITH | BETWEEN` The
following are descriptions of these comparison operators.
+ `EQ` : Equal. AttributeValueList can contain only one AttributeValue
of type String, Number, or Binary (not a set type). If an item
contains an AttributeValue element of a different type than the one
specified in the request, the value does not match. For example,
`{"S":"6"}` does not equal `{"N":"6"}`. Also, `{"N":"6"}` does not
equal `{"NS":["6", "2", "1"]}`.
+ `LE` : Less than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `LT` : Less than. AttributeValueList can contain only one
AttributeValue of type String, Number, or Binary (not a set type).
If an item contains an AttributeValue element of a different type
than the one specified in the request, the value does not match.
For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GE` : Greater than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GT` : Greater than. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `BEGINS_WITH` : Checks for a prefix. AttributeValueList can contain
only one AttributeValue of type String or Binary (not a Number or a
set type). The target attribute of the comparison must be of type
String or Binary (not a Number or a set type). > <li>
+ `BETWEEN` : Greater than or equal to the first value, and less than
or equal to the second value. AttributeValueList must contain two
AttributeValue elements of the same type, either String, Number, or
Binary (not a set type). A target attribute matches if the target
value is greater than, or equal to, the first element and less
than, or equal to, the second element. If an item contains an
AttributeValue element of a different type than the one specified
in the request, the value does not match. For example, `{"S":"6"}`
does not compare to `{"N":"6"}`. Also, `{"N":"6"}` does not compare
to `{"NS":["6", "2", "1"]}`
For usage examples of AttributeValueList and ComparisonOperator , see
`Legacy Conditional Parameters`_ in the Amazon DynamoDB Developer
Guide .
:type query_filter: map
:param query_filter:
There is a newer parameter available. Use FilterExpression instead.
Note that if you use QueryFilter and FilterExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A condition that evaluates the query results after the items are read
and returns only the desired values.
Query filters are applied after the items are read, so they do not
limit the capacity used.
If you specify more than one condition in the QueryFilter map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
QueryFilter does not allow key attributes. You cannot define a filter
condition on a hash key or range key.
Each QueryFilter element consists of an attribute name to compare,
along with the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
operator specified in ComparisonOperator . For type Number, value
comparisons are numeric. String value comparisons for greater than,
equals, or less than are based on ASCII character code values. For
example, `a` is greater than `A`, and `a` is greater than `B`. For
a list of code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For type Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions. For information on specifying data
types in JSON, see `JSON Data Format`_ in the Amazon DynamoDB
Developer Guide .
+ ComparisonOperator - A comparator for evaluating attributes. For
example, equals, greater than, less than, etc. The following
comparison operators are available: `EQ | NE | LE | LT | GE | GT |
NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN |
BETWEEN` For complete descriptions of all comparison operators, see
`API_Condition.html`_.
:type conditional_operator: string
:param conditional_operator:
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the QueryFilter map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type scan_index_forward: boolean
:param scan_index_forward: A value that specifies ascending (true) or
descending (false) traversal of the index. DynamoDB returns results
reflecting the requested order determined by the range key. If the
data type is Number, the results are returned in numeric order. For
type String, the results are returned in order of ASCII character
code values. For type Binary, DynamoDB treats each byte of the
binary data as unsigned when it compares binary values.
If ScanIndexForward is not specified, the results are returned in
ascending order.
:type exclusive_start_key: map
:param exclusive_start_key: The primary key of the first item that this
operation will evaluate. Use the value that was returned for
LastEvaluatedKey in the previous operation.
The data type for ExclusiveStartKey must be String, Number or Binary.
No set data types are allowed.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type projection_expression: string
:param projection_expression: A string that identifies one or more
attributes to retrieve from the table. These attributes can include
scalars, sets, or elements of a JSON document. The attributes in
the expression must be separated by commas.
If no attribute names are specified, then all attributes will be
returned. If any of the requested attributes are not found, they
will not appear in the result.
For more information on projection expressions, go to `Accessing Item
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type filter_expression: string
:param filter_expression: A condition that evaluates the query results
after the items are read and returns only the desired values.
The condition you specify is applied to the items queried; any items
that do not match the expression are not returned.
Filter expressions are applied after the items are read, so they do not
limit the capacity used.
A FilterExpression has the same syntax as a ConditionExpression . For
more information on expression syntax, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
"""
params = {
'TableName': table_name,
'KeyConditions': key_conditions,
}
if index_name is not None:
params['IndexName'] = index_name
if select is not None:
params['Select'] = select
if attributes_to_get is not None:
params['AttributesToGet'] = attributes_to_get
if limit is not None:
params['Limit'] = limit
if consistent_read is not None:
params['ConsistentRead'] = consistent_read
if query_filter is not None:
params['QueryFilter'] = query_filter
if conditional_operator is not None:
params['ConditionalOperator'] = conditional_operator
if scan_index_forward is not None:
params['ScanIndexForward'] = scan_index_forward
if exclusive_start_key is not None:
params['ExclusiveStartKey'] = exclusive_start_key
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if projection_expression is not None:
params['ProjectionExpression'] = projection_expression
if filter_expression is not None:
params['FilterExpression'] = filter_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
if expression_attribute_values is not None:
params['ExpressionAttributeValues'] = expression_attribute_values
return self.make_request(action='Query',
body=json.dumps(params))
def scan(self, table_name, attributes_to_get=None, limit=None,
select=None, scan_filter=None, conditional_operator=None,
exclusive_start_key=None, return_consumed_capacity=None,
total_segments=None, segment=None, projection_expression=None,
filter_expression=None, expression_attribute_names=None,
expression_attribute_values=None):
"""
The Scan operation returns one or more items and item
attributes by accessing every item in the table. To have
DynamoDB return fewer items, you can provide a ScanFilter
operation.
If the total number of scanned items exceeds the maximum data
set size limit of 1 MB, the scan stops and results are
returned to the user as a LastEvaluatedKey value to continue
the scan in a subsequent operation. The results also include
the number of items exceeding the limit. A scan can result in
no table data meeting the filter criteria.
The result set is eventually consistent.
By default, Scan operations proceed sequentially; however, for
faster performance on large tables, applications can request a
parallel Scan operation by specifying the Segment and
TotalSegments parameters. For more information, see `Parallel
Scan`_ in the Amazon DynamoDB Developer Guide .
:type table_name: string
:param table_name: The name of the table containing the requested
items.
:type attributes_to_get: list
:param attributes_to_get:
There is a newer parameter available. Use ProjectionExpression instead.
Note that if you use AttributesToGet and ProjectionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter allows you to retrieve lists or maps; however, it cannot
retrieve individual list or map elements.
The names of one or more attributes to retrieve. If no attribute names
are specified, then all attributes will be returned. If any of the
requested attributes are not found, they will not appear in the
result.
Note that AttributesToGet has no effect on provisioned throughput
consumption. DynamoDB determines capacity units consumed based on
item size, not on the amount of data that is returned to an
application.
:type limit: integer
:param limit: The maximum number of items to evaluate (not necessarily
the number of matching items). If DynamoDB processes the number of
items up to the limit while processing the results, it stops the
operation and returns the matching values up to that point, and a
key in LastEvaluatedKey to apply in a subsequent operation, so that
you can pick up where you left off. Also, if the processed data set
size exceeds 1 MB before DynamoDB reaches this limit, it stops the
operation and returns the matching values up to the limit, and a
key in LastEvaluatedKey to apply in a subsequent operation to
continue the operation. For more information, see `Query and Scan`_
in the Amazon DynamoDB Developer Guide .
:type select: string
:param select: The attributes to be returned in the result. You can
retrieve all item attributes, specific item attributes, or the
count of matching items.
+ `ALL_ATTRIBUTES` - Returns all of the item attributes.
+ `COUNT` - Returns the number of matching items, rather than the
matching items themselves.
+ `SPECIFIC_ATTRIBUTES` - Returns only the attributes listed in
AttributesToGet . This return value is equivalent to specifying
AttributesToGet without specifying any value for Select .
If neither Select nor AttributesToGet are specified, DynamoDB defaults
to `ALL_ATTRIBUTES`. You cannot use both AttributesToGet and Select
together in a single request, unless the value for Select is
`SPECIFIC_ATTRIBUTES`. (This usage is equivalent to specifying
AttributesToGet without any value for Select .)
:type scan_filter: map
:param scan_filter:
There is a newer parameter available. Use FilterExpression instead.
Note that if you use ScanFilter and FilterExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A condition that evaluates the scan results and returns only the
desired values.
If you specify more than one condition in the ScanFilter map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
Each ScanFilter element consists of an attribute name to compare, along
with the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
operator specified in ComparisonOperator . For type Number, value
comparisons are numeric. String value comparisons for greater than,
equals, or less than are based on ASCII character code values. For
example, `a` is greater than `A`, and `a` is greater than `B`. For
a list of code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions. For information on specifying data
types in JSON, see `JSON Data Format`_ in the Amazon DynamoDB
Developer Guide .
+ ComparisonOperator - A comparator for evaluating attributes. For
example, equals, greater than, less than, etc. The following
comparison operators are available: `EQ | NE | LE | LT | GE | GT |
NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN |
BETWEEN` For complete descriptions of all comparison operators, see
`Condition`_.
:type conditional_operator: string
:param conditional_operator:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use ConditionalOperator and ConditionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the ScanFilter map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type exclusive_start_key: map
:param exclusive_start_key: The primary key of the first item that this
operation will evaluate. Use the value that was returned for
LastEvaluatedKey in the previous operation.
The data type for ExclusiveStartKey must be String, Number or Binary.
No set data types are allowed.
In a parallel scan, a Scan request that includes ExclusiveStartKey must
specify the same segment whose previous Scan returned the
corresponding value of LastEvaluatedKey .
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type total_segments: integer
:param total_segments: For a parallel Scan request, TotalSegments
represents the total number of segments into which the Scan
operation will be divided. The value of TotalSegments corresponds
to the number of application workers that will perform the parallel
scan. For example, if you want to scan a table using four
application threads, specify a TotalSegments value of 4.
The value for TotalSegments must be greater than or equal to 1, and
less than or equal to 1000000. If you specify a TotalSegments value
of 1, the Scan operation will be sequential rather than parallel.
If you specify TotalSegments , you must also specify Segment .
:type segment: integer
:param segment: For a parallel Scan request, Segment identifies an
individual segment to be scanned by an application worker.
Segment IDs are zero-based, so the first segment is always 0. For
example, if you want to scan a table using four application
threads, the first thread specifies a Segment value of 0, the
second thread specifies 1, and so on.
The value of LastEvaluatedKey returned from a parallel Scan request
must be used as ExclusiveStartKey with the same segment ID in a
subsequent Scan operation.
The value for Segment must be greater than or equal to 0, and less than
the value provided for TotalSegments .
If you specify Segment , you must also specify TotalSegments .
:type projection_expression: string
:param projection_expression: A string that identifies one or more
attributes to retrieve from the table. These attributes can include
scalars, sets, or elements of a JSON document. The attributes in
the expression must be separated by commas.
If no attribute names are specified, then all attributes will be
returned. If any of the requested attributes are not found, they
will not appear in the result.
For more information on projection expressions, go to `Accessing Item
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type filter_expression: string
:param filter_expression: A condition that evaluates the scan results
and returns only the desired values.
The condition you specify is applied to the items scanned; any items
that do not match the expression are not returned.
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
"""
params = {'TableName': table_name, }
if attributes_to_get is not None:
params['AttributesToGet'] = attributes_to_get
if limit is not None:
params['Limit'] = limit
if select is not None:
params['Select'] = select
if scan_filter is not None:
params['ScanFilter'] = scan_filter
if conditional_operator is not None:
params['ConditionalOperator'] = conditional_operator
if exclusive_start_key is not None:
params['ExclusiveStartKey'] = exclusive_start_key
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if total_segments is not None:
params['TotalSegments'] = total_segments
if segment is not None:
params['Segment'] = segment
if projection_expression is not None:
params['ProjectionExpression'] = projection_expression
if filter_expression is not None:
params['FilterExpression'] = filter_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
if expression_attribute_values is not None:
params['ExpressionAttributeValues'] = expression_attribute_values
return self.make_request(action='Scan',
body=json.dumps(params))
def update_item(self, table_name, key, attribute_updates=None,
expected=None, conditional_operator=None,
return_values=None, return_consumed_capacity=None,
return_item_collection_metrics=None,
update_expression=None, condition_expression=None,
expression_attribute_names=None,
expression_attribute_values=None):
"""
Edits an existing item's attributes, or adds a new item to the
table if it does not already exist. You can put, delete, or
add attribute values. You can also perform a conditional
update (insert a new attribute name-value pair if it doesn't
exist, or replace an existing name-value pair if it has
certain expected attribute values).
You can also return the item's attribute values in the same
UpdateItem operation using the ReturnValues parameter.
:type table_name: string
:param table_name: The name of the table containing the item to update.
:type key: map
:param key: The primary key of the item to be updated. Each element
consists of an attribute name and a value for that attribute.
For the primary key, you must provide all of the attributes. For
example, with a hash type primary key, you only need to specify the
hash attribute. For a hash-and-range type primary key, you must
specify both the hash attribute and the range attribute.
:type attribute_updates: map
:param attribute_updates:
There is a newer parameter available. Use UpdateExpression instead.
Note that if you use AttributeUpdates and UpdateExpression at the
same time, DynamoDB will return a ValidationException exception.
This parameter can be used for modifying top-level attributes; however,
it does not support individual list or map elements.
The names of attributes to be modified, the action to perform on each,
and the new value for each. If you are updating an attribute that
is an index key attribute for any indexes on that table, the
attribute type must match the index key type defined in the
AttributesDefinition of the table description. You can use
UpdateItem to update any nonkey attributes.
Attribute values cannot be null. String and Binary type attributes must
have lengths greater than zero. Set type attributes must not be
empty. Requests with empty values will be rejected with a
ValidationException exception.
Each AttributeUpdates element consists of an attribute name to modify,
along with the following:
+ Value - The new value, if applicable, for this attribute.
+ Action - A value that specifies how to perform the update. This
action is only valid for an existing attribute whose data type is
Number or is a set; do not use `ADD` for other data types. If an
item with the specified primary key is found in the table, the
following values perform the following actions:
+ `PUT` - Adds the specified attribute to the item. If the attribute
already exists, it is replaced by the new value.
+ `DELETE` - Removes the attribute and its value, if no value is
specified for `DELETE`. The data type of the specified value must
match the existing value's data type. If a set of values is
specified, then those values are subtracted from the old set. For
example, if the attribute value was the set `[a,b,c]` and the
`DELETE` action specifies `[a,c]`, then the final attribute value
is `[b]`. Specifying an empty set is an error.
+ `ADD` - Adds the specified value to the item, if the attribute does
not already exist. If the attribute does exist, then the behavior
of `ADD` depends on the data type of the attribute:
+ If the existing attribute is a number, and if Value is also a number,
then Value is mathematically added to the existing attribute. If
Value is a negative number, then it is subtracted from the existing
attribute. If you use `ADD` to increment or decrement a number
value for an item that doesn't exist before the update, DynamoDB
uses 0 as the initial value. Similarly, if you use `ADD` for an
existing item to increment or decrement an attribute value that
doesn't exist before the update, DynamoDB uses `0` as the initial
value. For example, suppose that the item you want to update
doesn't have an attribute named itemcount , but you decide to `ADD`
the number `3` to this attribute anyway. DynamoDB will create the
itemcount attribute, set its initial value to `0`, and finally add
`3` to it. The result will be a new itemcount attribute, with a
value of `3`.
+ If the existing data type is a set, and if Value is also a set, then
Value is appended to the existing set. For example, if the
attribute value is the set `[1,2]`, and the `ADD` action specified
`[3]`, then the final attribute value is `[1,2,3]`. An error occurs
if an `ADD` action is specified for a set attribute and the
attribute type specified does not match the existing set type. Both
sets must have the same primitive data type. For example, if the
existing data type is a set of strings, Value must also be a set of
strings.
If no item with the specified key is found in the table, the following
values perform the following actions:
+ `PUT` - Causes DynamoDB to create a new item with the specified
primary key, and then adds the attribute.
+ `DELETE` - Nothing happens, because attributes cannot be deleted from
a nonexistent item. The operation succeeds, but DynamoDB does not
create a new item.
+ `ADD` - Causes DynamoDB to create an item with the supplied primary
key and number (or set of numbers) for the attribute value. The
only data types allowed are Number and Number Set.
If you specify any attributes that are part of an index key, then the
data types for those attributes must match those of the schema in
the table's attribute definition.
:type expected: map
:param expected:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use Expected and ConditionExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A map of attribute/condition pairs. Expected provides a conditional
block for the UpdateItem operation.
Each element of Expected consists of an attribute name, a comparison
operator, and one or more values. DynamoDB compares the attribute
with the value(s) you supplied, using the comparison operator. For
each Expected element, the result of the evaluation is either true
or false.
If you specify more than one element in the Expected map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
If the Expected map evaluates to true, then the conditional operation
succeeds; otherwise, it fails.
Expected contains the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
ComparisonOperator being used. For type Number, value comparisons
are numeric. String value comparisons for greater than, equals, or
less than are based on ASCII character code values. For example,
`a` is greater than `A`, and `a` is greater than `B`. For a list of
code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For type Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions.
+ ComparisonOperator - A comparator for evaluating attributes in the
AttributeValueList . When performing the comparison, DynamoDB uses
strongly consistent reads. The following comparison operators are
available: `EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL |
CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN | BETWEEN` The following
are descriptions of each comparison operator.
+ `EQ` : Equal. `EQ` is supported for all datatypes, including lists
and maps. AttributeValueList can contain only one AttributeValue
element of type String, Number, Binary, String Set, Number Set, or
Binary Set. If an item contains an AttributeValue element of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `NE` : Not equal. `NE` is supported for all datatypes, including
lists and maps. AttributeValueList can contain only one
AttributeValue of type String, Number, Binary, String Set, Number
Set, or Binary Set. If an item contains an AttributeValue of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `LE` : Less than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `LT` : Less than. AttributeValueList can contain only one
AttributeValue of type String, Number, or Binary (not a set type).
If an item contains an AttributeValue element of a different type
than the one specified in the request, the value does not match.
For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GE` : Greater than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GT` : Greater than. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `NOT_NULL` : The attribute exists. `NOT_NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
existence of an attribute, not its data type. If the data type of
attribute " `a`" is null, and you evaluate it using `NOT_NULL`, the
result is a Boolean true . This result is because the attribute "
`a`" exists; its data type is not relevant to the `NOT_NULL`
comparison operator.
+ `NULL` : The attribute does not exist. `NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
nonexistence of an attribute, not its data type. If the data type
of attribute " `a`" is null, and you evaluate it using `NULL`, the
result is a Boolean false . This is because the attribute " `a`"
exists; its data type is not relevant to the `NULL` comparison
operator.
+ `CONTAINS` : Checks for a subsequence, or value in a set.
AttributeValueList can contain only one AttributeValue element of
type String, Number, or Binary (not a set type). If the target
attribute of the comparison is of type String, then the operator
checks for a substring match. If the target attribute of the
comparison is of type Binary, then the operator looks for a
subsequence of the target that matches the input. If the target
attribute of the comparison is a set (" `SS`", " `NS`", or "
`BS`"), then the operator evaluates to true if it finds an exact
match with any member of the set. CONTAINS is supported for lists:
When evaluating " `a CONTAINS b`", " `a`" can be a list; however, "
`b`" cannot be a set, a map, or a list.
+ `NOT_CONTAINS` : Checks for absence of a subsequence, or absence of a
value in a set. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If the target attribute of the comparison is a String, then
the operator checks for the absence of a substring match. If the
target attribute of the comparison is Binary, then the operator
checks for the absence of a subsequence of the target that matches
the input. If the target attribute of the comparison is a set ("
`SS`", " `NS`", or " `BS`"), then the operator evaluates to true if
it does not find an exact match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating " `a NOT
CONTAINS b`", " `a`" can be a list; however, " `b`" cannot be a
set, a map, or a list.
+ `BEGINS_WITH` : Checks for a prefix. AttributeValueList can contain
only one AttributeValue of type String or Binary (not a Number or a
set type). The target attribute of the comparison must be of type
String or Binary (not a Number or a set type). > <li>
+ `IN` : Checks for matching elements within two sets.
AttributeValueList can contain one or more AttributeValue elements
of type String, Number, or Binary (not a set type). These
attributes are compared against an existing set type attribute of
an item. If any elements of the input set are present in the item
attribute, the expression evaluates to true.
+ `BETWEEN` : Greater than or equal to the first value, and less than
or equal to the second value. AttributeValueList must contain two
AttributeValue elements of the same type, either String, Number, or
Binary (not a set type). A target attribute matches if the target
value is greater than, or equal to, the first element and less
than, or equal to, the second element. If an item contains an
AttributeValue element of a different type than the one specified
in the request, the value does not match. For example, `{"S":"6"}`
does not compare to `{"N":"6"}`. Also, `{"N":"6"}` does not compare
to `{"NS":["6", "2", "1"]}`
For usage examples of AttributeValueList and ComparisonOperator , see
`Legacy Conditional Parameters`_ in the Amazon DynamoDB Developer
Guide .
For backward compatibility with previous DynamoDB releases, the
following parameters can be used instead of AttributeValueList and
ComparisonOperator :
+ Value - A value for DynamoDB to compare with an attribute.
+ Exists - A Boolean value that causes DynamoDB to evaluate the value
before attempting the conditional operation:
+ If Exists is `True`, DynamoDB will check to see if that attribute
value already exists in the table. If it is found, then the
condition evaluates to true; otherwise the condition evaluate to
false.
+ If Exists is `False`, DynamoDB assumes that the attribute value does
not exist in the table. If in fact the value does not exist, then
the assumption is valid and the condition evaluates to true. If the
value is found, despite the assumption that it does not exist, the
condition evaluates to false.
Note that the default value for Exists is `True`.
The Value and Exists parameters are incompatible with
AttributeValueList and ComparisonOperator . Note that if you use
both sets of parameters at once, DynamoDB will return a
ValidationException exception.
:type conditional_operator: string
:param conditional_operator:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use ConditionalOperator and ConditionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the Expected map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type return_values: string
:param return_values:
Use ReturnValues if you want to get the item attributes as they
appeared either before or after they were updated. For UpdateItem ,
the valid values are:
+ `NONE` - If ReturnValues is not specified, or if its value is `NONE`,
then nothing is returned. (This setting is the default for
ReturnValues .)
+ `ALL_OLD` - If UpdateItem overwrote an attribute name-value pair,
then the content of the old item is returned.
+ `UPDATED_OLD` - The old versions of only the updated attributes are
returned.
+ `ALL_NEW` - All of the attributes of the new version of the item are
returned.
+ `UPDATED_NEW` - The new versions of only the updated attributes are
returned.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type return_item_collection_metrics: string
:param return_item_collection_metrics: A value that if set to `SIZE`,
the response includes statistics about item collections, if any,
that were modified during the operation are returned in the
response. If set to `NONE` (the default), no statistics are
returned.
:type update_expression: string
:param update_expression: An expression that defines one or more
attributes to be updated, the action to be performed on them, and
new value(s) for them.
The following action values are available for UpdateExpression .
+ `SET` - Adds one or more attributes and values to an item. If any of
these attribute already exist, they are replaced by the new values.
You can also use `SET` to add or subtract from an attribute that is
of type Number. `SET` supports the following functions:
+ `if_not_exists (path, operand)` - if the item does not contain an
attribute at the specified path, then `if_not_exists` evaluates to
operand; otherwise, it evaluates to path. You can use this function
to avoid overwriting an attribute that may already be present in
the item.
+ `list_append (operand, operand)` - evaluates to a list with a new
element added to it. You can append the new element to the start or
the end of the list by reversing the order of the operands.
These function names are case-sensitive.
+ `REMOVE` - Removes one or more attributes from an item.
+ `ADD` - Adds the specified value to the item, if the attribute does
not already exist. If the attribute does exist, then the behavior
of `ADD` depends on the data type of the attribute:
+ If the existing attribute is a number, and if Value is also a number,
then Value is mathematically added to the existing attribute. If
Value is a negative number, then it is subtracted from the existing
attribute. If you use `ADD` to increment or decrement a number
value for an item that doesn't exist before the update, DynamoDB
uses `0` as the initial value. Similarly, if you use `ADD` for an
existing item to increment or decrement an attribute value that
doesn't exist before the update, DynamoDB uses `0` as the initial
value. For example, suppose that the item you want to update
doesn't have an attribute named itemcount , but you decide to `ADD`
the number `3` to this attribute anyway. DynamoDB will create the
itemcount attribute, set its initial value to `0`, and finally add
`3` to it. The result will be a new itemcount attribute in the
item, with a value of `3`.
+ If the existing data type is a set and if Value is also a set, then
Value is added to the existing set. For example, if the attribute
value is the set `[1,2]`, and the `ADD` action specified `[3]`,
then the final attribute value is `[1,2,3]`. An error occurs if an
`ADD` action is specified for a set attribute and the attribute
type specified does not match the existing set type. Both sets must
have the same primitive data type. For example, if the existing
data type is a set of strings, the Value must also be a set of
strings.
The `ADD` action only supports Number and set data types. In addition,
`ADD` can only be used on top-level attributes, not nested
attributes.
+ `DELETE` - Deletes an element from a set. If a set of values is
specified, then those values are subtracted from the old set. For
example, if the attribute value was the set `[a,b,c]` and the
`DELETE` action specifies `[a,c]`, then the final attribute value
is `[b]`. Specifying an empty set is an error. The `DELETE` action
only supports Number and set data types. In addition, `DELETE` can
only be used on top-level attributes, not nested attributes.
You can have many actions in a single expression, such as the
following: `SET a=:value1, b=:value2 DELETE :value3, :value4,
:value5`
For more information on update expressions, go to `Modifying Items and
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type condition_expression: string
:param condition_expression: A condition that must be satisfied in
order for a conditional update to succeed.
An expression can contain any of the following:
+ Boolean functions: `attribute_exists | attribute_not_exists |
contains | begins_with` These function names are case-sensitive.
+ Comparison operators: ` = | <> | < | > | <=
| >= | BETWEEN | IN`
+ Logical operators: `AND | OR | NOT`
For more information on condition expressions, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
"""
params = {'TableName': table_name, 'Key': key, }
if attribute_updates is not None:
params['AttributeUpdates'] = attribute_updates
if expected is not None:
params['Expected'] = expected
if conditional_operator is not None:
params['ConditionalOperator'] = conditional_operator
if return_values is not None:
params['ReturnValues'] = return_values
if return_consumed_capacity is not None:
params['ReturnConsumedCapacity'] = return_consumed_capacity
if return_item_collection_metrics is not None:
params['ReturnItemCollectionMetrics'] = return_item_collection_metrics
if update_expression is not None:
params['UpdateExpression'] = update_expression
if condition_expression is not None:
params['ConditionExpression'] = condition_expression
if expression_attribute_names is not None:
params['ExpressionAttributeNames'] = expression_attribute_names
if expression_attribute_values is not None:
params['ExpressionAttributeValues'] = expression_attribute_values
return self.make_request(action='UpdateItem',
body=json.dumps(params))
def update_table(self, table_name, provisioned_throughput=None,
global_secondary_index_updates=None,
attribute_definitions=None):
"""
Updates the provisioned throughput for the given table, or
manages the global secondary indexes on the table.
You can increase or decrease the table's provisioned
throughput values within the maximums and minimums listed in
the `Limits`_ section in the Amazon DynamoDB Developer Guide .
In addition, you can use UpdateTable to add, modify or delete
global secondary indexes on the table. For more information,
see `Managing Global Secondary Indexes`_ in the Amazon
DynamoDB Developer Guide .
The table must be in the `ACTIVE` state for UpdateTable to
succeed. UpdateTable is an asynchronous operation; while
executing the operation, the table is in the `UPDATING` state.
While the table is in the `UPDATING` state, the table still
has the provisioned throughput from before the call. The
table's new provisioned throughput settings go into effect
when the table returns to the `ACTIVE` state; at that point,
the UpdateTable operation is complete.
:type attribute_definitions: list
:param attribute_definitions: An array of attributes that describe the
key schema for the table and indexes. If you are adding a new
global secondary index to the table, AttributeDefinitions must
include the key element(s) of the new index.
:type table_name: string
:param table_name: The name of the table to be updated.
:type provisioned_throughput: dict
:param provisioned_throughput: Represents the provisioned throughput
settings for a specified table or index. The settings can be
modified using the UpdateTable operation.
For current minimum and maximum provisioned throughput values, see
`Limits`_ in the Amazon DynamoDB Developer Guide .
:type global_secondary_index_updates: list
:param global_secondary_index_updates:
An array of one or more global secondary indexes for the table. For
each index in the array, you can specify one action:
+ Create - add a new global secondary index to the table.
+ Update - modify the provisioned throughput settings of an existing
global secondary index.
+ Delete - remove a global secondary index from the table.
"""
params = {'TableName': table_name, }
if attribute_definitions is not None:
params['AttributeDefinitions'] = attribute_definitions
if provisioned_throughput is not None:
params['ProvisionedThroughput'] = provisioned_throughput
if global_secondary_index_updates is not None:
params['GlobalSecondaryIndexUpdates'] = global_secondary_index_updates
return self.make_request(action='UpdateTable',
body=json.dumps(params))
def make_request(self, action, body):
headers = {
'X-Amz-Target': '%s.%s' % (self.TargetPrefix, action),
'Host': self.host,
'Content-Type': 'application/x-amz-json-1.0',
'Content-Length': str(len(body)),
}
http_request = self.build_base_http_request(
method='POST', path='/', auth_path='/', params={},
headers=headers, data=body, host=self.host)
response = self._mexe(http_request, sender=None,
override_num_retries=self.NumberRetries,
retry_handler=self._retry_handler)
response_body = response.read().decode('utf-8')
boto.log.debug(response_body)
if response.status == 200:
if response_body:
return json.loads(response_body)
else:
json_body = json.loads(response_body)
fault_name = json_body.get('__type', None)
exception_class = self._faults.get(fault_name, self.ResponseError)
raise exception_class(response.status, response.reason,
body=json_body)
def _retry_handler(self, response, i, next_sleep):
status = None
boto.log.debug("Saw HTTP status: %s" % response.status)
if response.status == 400:
response_body = response.read().decode('utf-8')
boto.log.debug(response_body)
data = json.loads(response_body)
if 'ProvisionedThroughputExceededException' in data.get('__type'):
self.throughput_exceeded_events += 1
msg = "%s, retry attempt %s" % (
'ProvisionedThroughputExceededException',
i
)
next_sleep = self._truncated_exponential_time(i)
i += 1
status = (msg, i, next_sleep)
if i == self.NumberRetries:
# If this was our last retry attempt, raise
# a specific error saying that the throughput
# was exceeded.
raise exceptions.ProvisionedThroughputExceededException(
response.status, response.reason, data)
elif 'ConditionalCheckFailedException' in data.get('__type'):
raise exceptions.ConditionalCheckFailedException(
response.status, response.reason, data)
elif 'ValidationException' in data.get('__type'):
raise exceptions.ValidationException(
response.status, response.reason, data)
else:
raise self.ResponseError(response.status, response.reason,
data)
expected_crc32 = response.getheader('x-amz-crc32')
if self._validate_checksums and expected_crc32 is not None:
boto.log.debug('Validating crc32 checksum for body: %s',
response.read())
actual_crc32 = crc32(response.read()) & 0xffffffff
expected_crc32 = int(expected_crc32)
if actual_crc32 != expected_crc32:
msg = ("The calculated checksum %s did not match the expected "
"checksum %s" % (actual_crc32, expected_crc32))
status = (msg, i + 1, self._truncated_exponential_time(i))
return status
def _truncated_exponential_time(self, i):
if i == 0:
next_sleep = 0
else:
next_sleep = min(0.05 * (2 ** i),
boto.config.get('Boto', 'max_retry_delay', 60))
return next_sleep
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