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Manual Reference Pages  -  PAWS::DYNAMODB::QUERY (3)

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NAME

Paws::DynamoDB::Query - Arguments for method Query on Paws::DynamoDB

CONTENTS

DESCRIPTION

This class represents the parameters used for calling the method Query on the Amazon DynamoDB service. Use the attributes of this class as arguments to method Query.

You shouln’t make instances of this class. Each attribute should be used as a named argument in the call to Query.

As an example:



  $service_obj->Query(Att1 => $value1, Att2 => $value2, ...);



Values for attributes that are native types (Int, String, Float, etc) can passed as-is (scalar values). Values for complex Types (objects) can be passed as a HashRef. The keys and values of the hashref will be used to instance the underlying object.

ATTRIBUTES

    AttributesToGet => ArrayRef[Str]

This is a legacy parameter, for backward compatibility. New applications should use ProjectionExpression instead. Do not combine legacy parameters and expression parameters in a single API call; otherwise, DynamoDB will return a ValidationException exception.

This parameter allows you to retrieve attributes of type List or Map; however, it cannot retrieve individual elements within a List or a Map.

The names of one or more attributes to retrieve. If no attribute names are provided, 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.

    ConditionalOperator => Str

This is a legacy parameter, for backward compatibility. New applications should use FilterExpression instead. Do not combine legacy parameters and expression parameters in a single API call; otherwise, DynamoDB will return a ValidationException exception.

A logical operator to apply to the conditions in a QueryFilter map:
o AND - If all of the conditions evaluate to true, then the entire map evaluates to true.
o 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.

This parameter does not support attributes of type List or Map.

    ConsistentRead => Bool

Determines the read consistency model: If set to true, then the operation uses strongly consistent reads; otherwise, the operation uses eventually consistent reads.

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 a ValidationException.

    ExclusiveStartKey => Paws::DynamoDB::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.

    ExpressionAttributeNames => Paws::DynamoDB::ExpressionAttributeNameMap

One or more substitution tokens for attribute names in an expression. The following are some use cases for using ExpressionAttributeNames:
o To access an attribute whose name conflicts with a DynamoDB reserved word.
o To create a placeholder for repeating occurrences of an attribute name in an expression.
o To prevent special characters in an attribute name from being misinterpreted in an expression.
Use the <B> name. For example, consider the following attribute name:B>
o Percentile
The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see Reserved Words in the Amazon DynamoDB Developer Guide). To work around this, you could specify the following for ExpressionAttributeNames:
o {"
You could then use this substitution in an expression, as in this example:
o
Tokens that begin with the <B>:B> character are expression attribute values, which are placeholders for the actual value at runtime.

For more information on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

    ExpressionAttributeValues => Paws::DynamoDB::ExpressionAttributeValueMap

One or more values that can be substituted in an expression.

Use the <B>:B> (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, see Specifying Conditions in the Amazon DynamoDB Developer Guide.

    FilterExpression => Str

A string that contains conditions that DynamoDB applies after the Query operation, but before the data is returned to you. Items that do not satisfy the FilterExpression criteria are not returned.

A FilterExpression is applied after the items have already been read; the process of filtering does not consume any additional read capacity units.

For more information, see Filter Expressions in the Amazon DynamoDB Developer Guide.

FilterExpression replaces the legacy QueryFilter and ConditionalOperator parameters.

    IndexName => Str

The name of an index to query. This index can be any local secondary index or global secondary index on the table. Note that if you use the IndexName parameter, you must also provide TableName.

    KeyConditionExpression => Str

The condition that specifies the key value(s) for items to be retrieved by the Query action.

The condition must perform an equality test on a single hash key value. The condition can also perform one of several comparison tests on a single range key value. Query can use KeyConditionExpression to retrieve one item with a given hash and range key value, or several items that have the same hash key value but different range key values.

The hash key equality test is required, and must be specified in the following format:

hashAttributeName = :hashval

If you also want to provide a range key condition, it must be combined using AND with the hash key condition. Following is an example, using the <B>=B> comparison operator for the range key:

hashAttributeName = :hashval AND rangeAttributeName = :rangeval

Valid comparisons for the range key condition are as follows:
o rangeAttributeName = :rangeval - true if the range key is equal to :rangeval.
o rangeAttributeName < :rangeval - true if the range key is less than :rangeval.
o rangeAttributeName <= :rangeval - true if the range key is less than or equal to :rangeval.
o rangeAttributeName > :rangeval - true if the range key is greater than :rangeval.
o rangeAttributeName >= :rangeval - true if the range key is greater than or equal to :rangeval.
o rangeAttributeName BETWEEN :rangeval1 AND :rangeval2 - true if the range key is greater than or equal to :rangeval1, and less than or equal to :rangeval2.
o begins_with (rangeAttributeName, :rangeval) - true if the range key begins with a particular operand. (You cannot use this function with a range key that is of type Number.) Note that the function name begins_with is case-sensitive.
Use the ExpressionAttributeValues parameter to replace tokens such as :hashval and :rangeval with actual values at runtime.

You can optionally use the ExpressionAttributeNames parameter to replace the names of the hash and range attributes with placeholder tokens. This option might be necessary if an attribute name conflicts with a DynamoDB reserved word. For example, the following KeyConditionExpression parameter causes an error because Size is a reserved word:
o Size = :myval
To work around this, define a placeholder (such a the attribute name Size. KeyConditionExpression then is as follows:
o
For a list of reserved words, see Reserved Words in the Amazon DynamoDB Developer Guide.

For more information on ExpressionAttributeNames and ExpressionAttributeValues, see Using Placeholders for Attribute Names and Values in the Amazon DynamoDB Developer Guide.

KeyConditionExpression replaces the legacy KeyConditions parameter.

    KeyConditions => Paws::DynamoDB::KeyConditions

This is a legacy parameter, for backward compatibility. New applications should use KeyConditionExpression instead. Do not combine legacy parameters and expression parameters in a single API call; otherwise, DynamoDB will return a ValidationException exception.

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 provide the hash key attribute name and value as an EQ condition. You can optionally provide a second condition, referring to the range key attribute.

If you don’t provide a range key condition, all of the items that match the hash key will be retrieved. If a FilterExpression or QueryFilter is present, it will be applied after the items are retrieved.

For a query on an index, you can have conditions only on the index key attributes. You must provide the index hash attribute name and value as an EQ condition. You can optionally provide a second condition, referring to the index key range attribute.

Each KeyConditions element consists of an attribute name to compare, along with the following:
o 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

For Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values.

o 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.
o 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"]}.

o 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 provided 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"]}.

o 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 provided 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"]}.

o 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 provided 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"]}.

o 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 provided 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"]}.

o 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).

o 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 provided 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.

    Limit => Int

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.

    ProjectionExpression => Str

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, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

ProjectionExpression replaces the legacy AttributesToGet parameter.

    QueryFilter => Paws::DynamoDB::FilterConditionMap

This is a legacy parameter, for backward compatibility. New applications should use FilterExpression instead. Do not combine legacy parameters and expression parameters in a single API call; otherwise, DynamoDB will return a ValidationException exception.

A condition that evaluates the query results after the items are read and returns only the desired values.

This parameter does not support attributes of type List or Map.

A QueryFilter is applied after the items have already been read; the process of filtering does not consume any additional read capacity units.

If you provide 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.)

Note that 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:
o 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

For type Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values.

For information on specifying data types in JSON, see JSON Data Format in the Amazon DynamoDB Developer Guide.

o 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 the Condition data type.

    ReturnConsumedCapacity => Str

    ScanIndexForward => Bool

Specifies the order in which to return the query results - either ascending (true) or descending (false).

Items with the same hash key are stored in sorted order by range key .If the range key data type is Number, the results are stored 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.

If ScanIndexForward is true, DynamoDB returns the results in order, by range key. This is the default behavior.

If ScanIndexForward is false, DynamoDB sorts the results in descending order by range key, and then returns the results to the client.

    Select => Str

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.
o 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.
o 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.
o COUNT - Returns the number of matching items, rather than the matching items themselves.
o 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.)

If you use the ProjectionExpression parameter, then the value for Select can only be SPECIFIC_ATTRIBUTES. Any other value for Select will return an error.

REQUIRED TableName => Str

The name of the table containing the requested items.

SEE ALSO

This class forms part of Paws, documenting arguments for method Query in Paws::DynamoDB

BUGS and CONTRIBUTIONS

The source code is located here: https://github.com/pplu/aws-sdk-perl

Please report bugs to: https://github.com/pplu/aws-sdk-perl/issues

POD ERRORS

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