NAME
Paws::DynamoDB::Query - Arguments for method Query on Paws::DynamoDB
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 shouldn't make instances of this class. Each attribute should be used as a named argument in the call to Query.
SYNOPSIS
my $dynamodb = Paws->service('DynamoDB');
# To query an item
# This example queries items in the Music table. The table has a partition key
# and sort key (Artist and SongTitle), but this query only specifies the
# partition key value. It returns song titles by the artist named "No One You
# Know".
my $QueryOutput = $dynamodb->Query(
'ExpressionAttributeValues' => {
':v1' => {
'S' => 'No One You Know'
}
},
'KeyConditionExpression' => 'Artist = :v1',
'ProjectionExpression' => 'SongTitle',
'TableName' => 'Music'
);
# Results:
my $ConsumedCapacity = $QueryOutput->ConsumedCapacity;
my $Count = $QueryOutput->Count;
my $Items = $QueryOutput->Items;
my $ScannedCount = $QueryOutput->ScannedCount;
# Returns a L<Paws::DynamoDB::QueryOutput> object.
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. For the AWS API documentation, see https://docs.aws.amazon.com/goto/WebAPI/dynamodb/Query
ATTRIBUTES
AttributesToGet => ArrayRef[Str|Undef]
This is a legacy parameter. Use ProjectionExpression
instead. For more information, see AttributesToGet (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html) in the Amazon DynamoDB Developer Guide.
ConditionalOperator => Str
This is a legacy parameter. Use FilterExpression
instead. For more information, see ConditionalOperator (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.ConditionalOperator.html) in the Amazon DynamoDB Developer Guide.
Valid values are: "AND"
, "OR"
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
:
To access an attribute whose name conflicts with a DynamoDB reserved word.
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 attribute name:
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 (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html) in the Amazon DynamoDB Developer Guide). To work around this, you could specify the following for ExpressionAttributeNames
:
{"#P":"Percentile"}
You could then use this substitution in an expression, as in this example:
#P = :val
Tokens that begin with the : character are expression attribute values, which are placeholders for the actual value at runtime.
For more information on expression attribute names, see Specifying Item Attributes (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html) in the Amazon DynamoDB Developer Guide.
ExpressionAttributeValues => Paws::DynamoDB::ExpressionAttributeValueMap
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, see Specifying Conditions (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.SpecifyingConditions.html) 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
does not allow key attributes. You cannot define a filter expression based on a partition key or a sort key.
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 (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html#FilteringResults) in the Amazon DynamoDB Developer Guide.
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 values for items to be retrieved by the Query
action.
The condition must perform an equality test on a single partition key value.
The condition can optionally perform one of several comparison tests on a single sort key value. This allows Query
to retrieve one item with a given partition key value and sort key value, or several items that have the same partition key value but different sort key values.
The partition key equality test is required, and must be specified in the following format:
partitionKeyName
= :partitionkeyval
If you also want to provide a condition for the sort key, it must be combined using AND
with the condition for the sort key. Following is an example, using the = comparison operator for the sort key:
partitionKeyName
=
:partitionkeyval
AND
sortKeyName
=
:sortkeyval
Valid comparisons for the sort key condition are as follows:
sortKeyName
=
:sortkeyval
- true if the sort key value is equal to:sortkeyval
.sortKeyName
<
:sortkeyval
- true if the sort key value is less than:sortkeyval
.sortKeyName
<=
:sortkeyval
- true if the sort key value is less than or equal to:sortkeyval
.sortKeyName
>
:sortkeyval
- true if the sort key value is greater than:sortkeyval
.sortKeyName
>=
:sortkeyval
- true if the sort key value is greater than or equal to:sortkeyval
.sortKeyName
BETWEEN
:sortkeyval1
AND
:sortkeyval2
- true if the sort key value is greater than or equal to:sortkeyval1
, and less than or equal to:sortkeyval2
.begins_with (
sortKeyName
,:sortkeyval
)
- true if the sort key value begins with a particular operand. (You cannot use this function with a sort key that is of type Number.) Note that the function namebegins_with
is case-sensitive.
Use the ExpressionAttributeValues
parameter to replace tokens such as :partitionval
and :sortval
with actual values at runtime.
You can optionally use the ExpressionAttributeNames
parameter to replace the names of the partition key and sort key 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:
Size = :myval
To work around this, define a placeholder (such a #S
) to represent the attribute name Size. KeyConditionExpression
then is as follows:
#S = :myval
For a list of reserved words, see Reserved Words (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html) in the Amazon DynamoDB Developer Guide.
For more information on ExpressionAttributeNames
and ExpressionAttributeValues
, see Using Placeholders for Attribute Names and Values (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ExpressionPlaceholders.html) in the Amazon DynamoDB Developer Guide.
KeyConditions => Paws::DynamoDB::KeyConditions
This is a legacy parameter. Use KeyConditionExpression
instead. For more information, see KeyConditions (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.KeyConditions.html) 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 dataset 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 (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html) 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 (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html) in the Amazon DynamoDB Developer Guide.
QueryFilter => Paws::DynamoDB::FilterConditionMap
This is a legacy parameter. Use FilterExpression
instead. For more information, see QueryFilter (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.QueryFilter.html) in the Amazon DynamoDB Developer Guide.
ReturnConsumedCapacity => Str
Valid values are: "INDEXES"
, "TOTAL"
, "NONE"
ScanIndexForward => Bool
Specifies the order for index traversal: If true
(default), the traversal is performed in ascending order; if false
, the traversal is performed in descending order.
Items with the same partition key value are stored in sorted order by sort key. If the sort key data type is Number, the results are stored in numeric order. For type String, the results are stored in order of UTF-8 bytes. For type Binary, DynamoDB treats each byte of the binary data as unsigned.
If ScanIndexForward
is true
, DynamoDB returns the results in the order in which they are stored (by sort key value). This is the default behavior. If ScanIndexForward
is false
, DynamoDB reads the results in reverse order by sort key value, 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.
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 fetches 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 specifyingALL_ATTRIBUTES
.COUNT
- Returns the number of matching items, rather than the matching items themselves.SPECIFIC_ATTRIBUTES
- Returns only the attributes listed inAttributesToGet
. This return value is equivalent to specifyingAttributesToGet
without specifying any value forSelect
.If you query or scan 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 fetches each of these attributes from the parent table. This extra fetching incurs additional throughput cost and latency.
If you query or scan 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.
Valid values are: "ALL_ATTRIBUTES"
, "ALL_PROJECTED_ATTRIBUTES"
, "SPECIFIC_ATTRIBUTES"
, "COUNT"
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