Struct aws_sdk_dynamodb::client::fluent_builders::Scan
source · [−]pub struct Scan<C = DynConnector, M = DefaultMiddleware, R = Standard> { /* private fields */ }
Expand description
Fluent builder constructing a request to Scan
.
The Scan
operation returns one or more items and item attributes by accessing every item in a table or a secondary index. To have DynamoDB return fewer items, you can provide a FilterExpression
operation.
If the total number of scanned items exceeds the maximum dataset 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.
A single Scan
operation reads up to the maximum number of items set (if using the Limit
parameter) or a maximum of 1 MB of data and then apply any filtering to the results using FilterExpression
. If LastEvaluatedKey
is present in the response, you need to paginate the result set. For more information, see Paginating the Results in the Amazon DynamoDB Developer Guide.
Scan
operations proceed sequentially; however, for faster performance on a large table or secondary index, applications can request a parallel Scan
operation by providing the Segment
and TotalSegments
parameters. For more information, see Parallel Scan in the Amazon DynamoDB Developer Guide.
Scan
uses eventually consistent reads when accessing the data in a table; therefore, the result set might not include the changes to data in the table immediately before the operation began. If you need a consistent copy of the data, as of the time that the Scan
begins, you can set the ConsistentRead
parameter to true
.
Implementations
impl<C, M, R> Scan<C, M, R> where
C: SmithyConnector,
M: SmithyMiddleware<C>,
R: NewRequestPolicy,
impl<C, M, R> Scan<C, M, R> where
C: SmithyConnector,
M: SmithyMiddleware<C>,
R: NewRequestPolicy,
pub async fn send(self) -> Result<ScanOutput, SdkError<ScanError>> where
R::Policy: SmithyRetryPolicy<ScanInputOperationOutputAlias, ScanOutput, ScanError, ScanInputOperationRetryAlias>,
pub async fn send(self) -> Result<ScanOutput, SdkError<ScanError>> where
R::Policy: SmithyRetryPolicy<ScanInputOperationOutputAlias, ScanOutput, ScanError, ScanInputOperationRetryAlias>,
Sends the request and returns the response.
If an error occurs, an SdkError
will be returned with additional details that
can be matched against.
By default, any retryable failures will be retried twice. Retry behavior is configurable with the RetryConfig, which can be set when configuring the client.
Create a paginator for this request
Paginators are used by calling send().await
which returns a Stream
.
The name of the table containing the requested items; or, if you provide IndexName
, the name of the table to which that index belongs.
The name of the table containing the requested items; or, if you provide IndexName
, the name of the table to which that index belongs.
The name of a secondary index to scan. This index can be any local secondary index or global secondary index. Note that if you use the IndexName
parameter, you must also provide TableName
.
The name of a secondary index to scan. This index can be any local secondary index or global secondary index. Note that if you use the IndexName
parameter, you must also provide TableName
.
Appends an item to AttributesToGet
.
To override the contents of this collection use set_attributes_to_get
.
This is a legacy parameter. Use ProjectionExpression
instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use ProjectionExpression
instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.
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 Working with Queries in the Amazon DynamoDB Developer Guide.
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 Working with Queries in the Amazon DynamoDB Developer Guide.
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 reads 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.
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 reads 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.
Adds a key-value pair to ScanFilter
.
To override the contents of this collection use set_scan_filter
.
This is a legacy parameter. Use FilterExpression
instead. For more information, see ScanFilter in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use FilterExpression
instead. For more information, see ScanFilter in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.
Adds a key-value pair to ExclusiveStartKey
.
To override the contents of this collection use set_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
.
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
.
Determines the level of detail about either provisioned or on-demand throughput consumption that is returned in the response:
-
INDEXES
- The response includes the aggregateConsumedCapacity
for the operation, together withConsumedCapacity
for each table and secondary index that was accessed.Note that some operations, such as
GetItem
andBatchGetItem
, do not access any indexes at all. In these cases, specifyingINDEXES
will only returnConsumedCapacity
information for table(s). -
TOTAL
- The response includes only the aggregateConsumedCapacity
for the operation. -
NONE
- NoConsumedCapacity
details are included in the response.
Determines the level of detail about either provisioned or on-demand throughput consumption that is returned in the response:
-
INDEXES
- The response includes the aggregateConsumedCapacity
for the operation, together withConsumedCapacity
for each table and secondary index that was accessed.Note that some operations, such as
GetItem
andBatchGetItem
, do not access any indexes at all. In these cases, specifyingINDEXES
will only returnConsumedCapacity
information for table(s). -
TOTAL
- The response includes only the aggregateConsumedCapacity
for the operation. -
NONE
- NoConsumedCapacity
details are included in the response.
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 use four application threads to scan a table or an index, 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
.
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 use four application threads to scan a table or an index, 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
.
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 use four application threads to scan a table or an index, then 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 provide Segment
, you must also provide TotalSegments
.
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 use four application threads to scan a table or an index, then 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 provide Segment
, you must also provide TotalSegments
.
A string that identifies one or more attributes to retrieve from the specified table or index. 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 Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
A string that identifies one or more attributes to retrieve from the specified table or index. 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 Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
A string that contains conditions that DynamoDB applies after the Scan
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.
A string that contains conditions that DynamoDB applies after the Scan
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.
Adds a key-value pair to ExpressionAttributeNames
.
To override the contents of this collection use set_expression_attribute_names
.
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:
-
#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 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:
-
#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 in the Amazon DynamoDB Developer Guide.
Adds a key-value pair to ExpressionAttributeValues
.
To override the contents of this collection use set_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, see Condition Expressions in the Amazon DynamoDB Developer Guide.
pub fn set_expression_attribute_values(
self,
input: Option<HashMap<String, AttributeValue>>
) -> Self
pub fn set_expression_attribute_values(
self,
input: Option<HashMap<String, AttributeValue>>
) -> Self
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 Condition Expressions in the Amazon DynamoDB Developer Guide.
A Boolean value that determines the read consistency model during the scan:
-
If
ConsistentRead
isfalse
, then the data returned fromScan
might not contain the results from other recently completed write operations (PutItem
,UpdateItem
, orDeleteItem
). -
If
ConsistentRead
istrue
, then all of the write operations that completed before theScan
began are guaranteed to be contained in theScan
response.
The default setting for ConsistentRead
is false
.
The ConsistentRead
parameter is not supported on global secondary indexes. If you scan a global secondary index with ConsistentRead
set to true, you will receive a ValidationException
.
A Boolean value that determines the read consistency model during the scan:
-
If
ConsistentRead
isfalse
, then the data returned fromScan
might not contain the results from other recently completed write operations (PutItem
,UpdateItem
, orDeleteItem
). -
If
ConsistentRead
istrue
, then all of the write operations that completed before theScan
began are guaranteed to be contained in theScan
response.
The default setting for ConsistentRead
is false
.
The ConsistentRead
parameter is not supported on global secondary indexes. If you scan a global secondary index with ConsistentRead
set to true, you will receive a ValidationException
.
Trait Implementations
Auto Trait Implementations
impl<C = DynConnector, M = DefaultMiddleware, R = Standard> !RefUnwindSafe for Scan<C, M, R>
impl<C = DynConnector, M = DefaultMiddleware, R = Standard> !UnwindSafe for Scan<C, M, R>
Blanket Implementations
Mutably borrows from an owned value. Read more
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more