query — Boto3 Docs 1.26.86 documentation

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 specifying ALL_ATTRIBUTES .
• COUNT - Returns the number of matching items, rather than the matching items themselves. Note that this uses the same quantity of read capacity units as getting the items, and is subject to the same item size calculations.
• SPECIFIC_ATTRIBUTES - Returns only the attributes listed in ProjectionExpression . This return value is equivalent to specifying ProjectionExpression without specifying any value for Select . 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 ProjectionExpression 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 ProjectionExpression together in a single request, unless the value for Select is SPECIFIC_ATTRIBUTES . (This usage is equivalent to specifying ProjectionExpression without any value for Select .)

Note

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.

This is a legacy parameter. Use ProjectionExpression instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide .

• (string) --

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 .

This is a legacy parameter. Use KeyConditionExpression instead. For more information, see KeyConditions in the Amazon DynamoDB Developer Guide .

• (string) --

This is a legacy parameter. Use FilterExpression instead. For more information, see QueryFilter in the Amazon DynamoDB Developer Guide .

• (string) --

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.

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.

• (string) --
  • (valid DynamoDB type) -- - The value of the attribute. The valid value types are listed in the DynamoDB Reference Guide.

Determines the level of detail about either provisioned or on-demand throughput consumption that is returned in the response:

• INDEXES - The response includes the aggregate ConsumedCapacity for the operation, together with ConsumedCapacity for each table and secondary index that was accessed. Note that some operations, such as GetItem and BatchGetItem , do not access any indexes at all. In these cases, specifying INDEXES will only return ConsumedCapacity information for table(s).
• TOTAL - The response includes only the aggregate ConsumedCapacity for the operation.
• NONE - No ConsumedCapacity details are included in the response.

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 .

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 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:

Note

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 in the Amazon DynamoDB Developer Guide .

• (string) --
  • (string) --

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 in the Amazon DynamoDB Developer Guide .

• (string) --
  • (valid DynamoDB type) -- - The value of the attribute. The valid value types are listed in the DynamoDB Reference Guide.