Amazon DynamoDB
API Reference (API Version 2012-08-10)
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Query

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 read capacity units according to the type of read.

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 a LastEvaluatedKey to continue the query in a subsequent operation. Unlike a Scan operation, a Query operation never returns 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.

Request Syntax

{
    "AttributesToGet": [
        "string"
    ],
    "ConditionalOperator": "string",
    "ConsistentRead": "boolean",
    "ExclusiveStartKey": 
        {
            "string" :
                {
                    "B": "blob",
                    "BS": [
                        "blob"
                    ],
                    "N": "string",
                    "NS": [
                        "string"
                    ],
                    "S": "string",
                    "SS": [
                        "string"
                    ]
                }
        },
    "IndexName": "string",
    "KeyConditions": 
        {
            "string" :
                {
                    "AttributeValueList": [
                        {
                            "B": "blob",
                            "BS": [
                                "blob"
                            ],
                            "N": "string",
                            "NS": [
                                "string"
                            ],
                            "S": "string",
                            "SS": [
                                "string"
                            ]
                        }
                    ],
                    "ComparisonOperator": "string"
                }
        },
    "Limit": "number",
    "QueryFilter": 
        {
            "string" :
                {
                    "AttributeValueList": [
                        {
                            "B": "blob",
                            "BS": [
                                "blob"
                            ],
                            "N": "string",
                            "NS": [
                                "string"
                            ],
                            "S": "string",
                            "SS": [
                                "string"
                            ]
                        }
                    ],
                    "ComparisonOperator": "string"
                }
        },
    "ReturnConsumedCapacity": "string",
    "ScanIndexForward": "boolean",
    "Select": "string",
    "TableName": "string"
}
			

Request Parameters

The request accepts the following data in JSON format.

Note

In the following list, the required parameters are described first.

KeyConditions

The selection criteria for the query.

For a query on a table, you can only have conditions 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.

For a query on an index, you can only have conditions 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 aa 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, etc.

    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). 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"]}.

    • LE : Less than or equal.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a 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 compare to {"NS":["6", "2", "1"]}.

    • LT : Less than.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a 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 compare to {"NS":["6", "2", "1"]}.

    • GE : Greater than or equal.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a 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 compare to {"NS":["6", "2", "1"]}.

    • GT : Greater than.

      AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a 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 compare to {"NS":["6", "2", "1"]}.

    • BEGINS_WITH : checks for a prefix.

      AttributeValueList can contain only one AttributeValue of type String or Binary (not a Number or a set). The target attribute of the comparison must be a String or Binary (not a Number or a set).

    • 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). 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 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 Conditional Expressions in the Amazon DynamoDB Developer Guide.

Type: String to Condition object map

Required: Yes

TableName

The name of the table containing the requested items.

Type: String

Length constraints: Minimum length of 3. Maximum length of 255.

Required: Yes

AttributesToGet

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 are querying 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 are querying 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: array of Strings

Length constraints: Minimum of 1 item(s) in the list.

Required: No

ConditionalOperator

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: String

Valid Values: AND | OR

Required: No

ConsistentRead

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: Boolean

Required: No

ExclusiveStartKey

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: String to AttributeValue object map

Required: No

IndexName

The name of an index to query. This can be any local secondary index or global secondary index on the table.

Type: String

Length constraints: Minimum length of 3. Maximum length of 255.

Required: No

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 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 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: Number

Required: No

QueryFilter

Evaluates the query results and returns only the desired values.

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.)

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 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 aa 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 API_Condition.html.

Type: String to Condition object map

Required: No

ReturnConsumedCapacity

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: String

Valid Values: INDEXES | TOTAL | NONE

Required: No

ScanIndexForward

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 String, the results are returned in order of ASCII character code values. For 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: Boolean

Required: No

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 are querying 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 which have been projected into the index. If the index is configured to project all attributes, this 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 is equivalent to specifying AttributesToGet without specifying any value for Select.

    If you are querying 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 are querying 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: String

Valid Values: ALL_ATTRIBUTES | ALL_PROJECTED_ATTRIBUTES | SPECIFIC_ATTRIBUTES | COUNT

Required: No

Response Syntax

{
    "ConsumedCapacity": {
        "CapacityUnits": "number",
        "GlobalSecondaryIndexes": 
            {
                "string" :
                    {
                        "CapacityUnits": "number"
                    }
            },
        "LocalSecondaryIndexes": 
            {
                "string" :
                    {
                        "CapacityUnits": "number"
                    }
            },
        "Table": {
            "CapacityUnits": "number"
        },
        "TableName": "string"
    },
    "Count": "number",
    "Items": [
        
            {
                "string" :
                    {
                        "B": "blob",
                        "BS": [
                            "blob"
                        ],
                        "N": "string",
                        "NS": [
                            "string"
                        ],
                        "S": "string",
                        "SS": [
                            "string"
                        ]
                    }
            }
    ],
    "LastEvaluatedKey": 
        {
            "string" :
                {
                    "B": "blob",
                    "BS": [
                        "blob"
                    ],
                    "N": "string",
                    "NS": [
                        "string"
                    ],
                    "S": "string",
                    "SS": [
                        "string"
                    ]
                }
        },
    "ScannedCount": "number"
}
			

Response Elements

The following data is returned in JSON format by the service.

ConsumedCapacity

Represents the capacity units consumed by an operation. The data returned includes the total provisioned throughput consumed, along with statistics for the table and any indexes involved in the operation. ConsumedCapacity is only returned if it was asked for in the request. For more information, see Provisioned Throughput in the Amazon DynamoDB Developer Guide.

Type: ConsumedCapacity object

Count

The number of items in the response.

If you used a QueryFilter in the request, then Count is the number of items returned after the filter was applied, and ScannedCount is the number of matching items before the filter was applied.

If you did not use a filter in the request, then Count and ScannedCount are the same.

Type: Number

Items

An array of item attributes that match the query criteria. Each element in this array consists of an attribute name and the value for that attribute.

Type: array of s

LastEvaluatedKey

The primary key of the item where the operation stopped, inclusive of the previous result set. Use this value to start a new operation, excluding this value in the new request.

If LastEvaluatedKey is empty, then the "last page" of results has been processed and there is no more data to be retrieved.

If LastEvaluatedKey is not empty, this does not necessarily mean that there is more data in the result set. The only way to know when you have reached the end of the result set is when LastEvaluatedKey is empty.

Type: String to AttributeValue object map

ScannedCount

The number of items evaluated, before any QueryFilter is applied. A high ScannedCount value with few, or no, Count results indicates an inefficient Query operation. For more information, see Count and ScannedCount in the Amazon DynamoDB Developer Guide.

If you did not use a filter in the request, then ScannedCount is the same as Count.

Type: Number

Errors

For information about the errors that are common to all actions, see Common Errors.

InternalServerError

An error occurred on the server side.

HTTP Status Code: 500

ProvisionedThroughputExceededException

The request rate is too high, or the request is too large, for the available throughput to accommodate. The AWS SDKs automatically retry requests that receive this exception; therefore, your request will eventually succeed, unless the request is too large or your retry queue is too large to finish. Reduce the frequency of requests by using the strategies listed in Error Retries and Exponential Backoff in the Amazon DynamoDB Developer Guide.

HTTP Status Code: 400

ResourceNotFoundException

The operation tried to access a nonexistent table or index. The resource may not be specified correctly, or its status may not be ACTIVE.

HTTP Status Code: 400

Examples

Retrieving a Range of Items

This example queries the Thread table for postings between two dates. There is an index on LastPostDateTime to facilitate fast lookups on this attribute. All of the attributes will be returned. Any attributes that are not projected into the index will cause DynamoDB to fetch those attributes from the Thread table; this fetching occurs automatically.

Sample Request

POST / HTTP/1.1
Host: dynamodb.<region>.<domain>;
X-Amz-Date: <Date>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=content-length;content-type;host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-target, Signature=<Signature>
User-Agent: <UserAgentString>
x-amz-content-sha256: <PayloadHash>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>     
Connection: Keep-Alive X-Amz-Target: DynamoDB_20120810.Query 

{
    "TableName": "Thread",
    "IndexName": "LastPostIndex",
    "Select": "ALL_ATTRIBUTES",
    "Limit":3,
    "ConsistentRead": true,
    "KeyConditions": {
        "LastPostDateTime": {
            "AttributeValueList": [
                {
                    "S": "20130101"
                },
                {
                    "S": "20130115"
                }
            ],
            "ComparisonOperator": "BETWEEN"
        },
        "ForumName": {
            "AttributeValueList": [
                {
                    "S": "Amazon DynamoDB"
                }
            ],
            "ComparisonOperator": "EQ"
        }
    },
    "ReturnConsumedCapacity": "TOTAL"
}
        

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId> 
x-amz-crc32: <Checksum>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
Date: <Date>
 {
    "Count": 3,
    "Items": [
        {
            "LastPostedBy": {
                "S": "fred@example.com"
            },
            "ForumName": {
                "S": "Amazon DynamoDB"
            },
            "LastPostDateTime": {
                "S": "20130102054211"
            },
            "Tags": {
                "SS": ["Problem","Question"]
            }
        },
        {
            "LastPostedBy": {
                "S": "alice@example.com"
            },
            "ForumName": {
                "S": "Amazon DynamoDB"
            },
            "LastPostDateTime": {
                    "S": "20130105111307"
            },
            "Tags": {
                "SS": ["Idea"]
            }
        },
        {
            "LastPostedBy": {
                "S": "bob@example.com"
            },
            "ForumName": {
                "S": "Amazon DynamoDB"
            },
            "LastPostDateTime": {
                "S": "20130108094417"
            },
            "Tags": {
                "SS": ["AppDesign", "HelpMe"]
            }
        }
    ],
    "ConsumedCapacity": {
        "TableName": "Thread",
        "CapacityUnits": 1
    }
}
        

Counting Items

This example returns the number of items in the Thread table for a particular forum.

Sample Request

POST / HTTP/1.1
Host: dynamodb.<region>.<domain>;
X-Amz-Date: <Date>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=content-length;content-type;host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-target, Signature=<Signature>
User-Agent: <UserAgentString>
x-amz-content-sha256: <PayloadHash>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>     
Connection: Keep-Alive X-Amz-Target: DynamoDB_20120810.Query 

{
    "TableName": "Thread",
    "Select": "COUNT",
    "ConsistentRead": true,
    "KeyConditions": {
        "ForumName": {
            "AttributeValueList": [
                {
                    "S": "Amazon DynamoDB"
                }
            ],
            "ComparisonOperator": "EQ"
        }
    }
}
        

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId> 
x-amz-crc32: <Checksum>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
Date: <Date>
 {
    "Count":`17
}