@Generated(value="software.amazon.awssdk:codegen") public final class QueryRequest extends DynamoDbRequest implements ToCopyableBuilder<QueryRequest.Builder,QueryRequest>
Represents the input of a Query
operation.
Modifier and Type | Class and Description |
---|---|
static interface |
QueryRequest.Builder |
Modifier and Type | Method and Description |
---|---|
List<String> |
attributesToGet()
This is a legacy parameter.
|
static QueryRequest.Builder |
builder() |
ConditionalOperator |
conditionalOperator()
This is a legacy parameter.
|
String |
conditionalOperatorAsString()
This is a legacy parameter.
|
Boolean |
consistentRead()
Determines the read consistency model: If set to
true , then the operation uses strongly consistent
reads; otherwise, the operation uses eventually consistent reads. |
boolean |
equals(Object obj) |
boolean |
equalsBySdkFields(Object obj) |
Map<String,AttributeValue> |
exclusiveStartKey()
The primary key of the first item that this operation will evaluate.
|
Map<String,String> |
expressionAttributeNames()
One or more substitution tokens for attribute names in an expression.
|
Map<String,AttributeValue> |
expressionAttributeValues()
One or more values that can be substituted in an expression.
|
String |
filterExpression()
A string that contains conditions that DynamoDB applies after the
Query operation, but before the
data is returned to you. |
<T> Optional<T> |
getValueForField(String fieldName,
Class<T> clazz) |
boolean |
hasAttributesToGet()
For responses, this returns true if the service returned a value for the AttributesToGet property.
|
boolean |
hasExclusiveStartKey()
For responses, this returns true if the service returned a value for the ExclusiveStartKey property.
|
boolean |
hasExpressionAttributeNames()
For responses, this returns true if the service returned a value for the ExpressionAttributeNames property.
|
boolean |
hasExpressionAttributeValues()
For responses, this returns true if the service returned a value for the ExpressionAttributeValues property.
|
int |
hashCode() |
boolean |
hasKeyConditions()
For responses, this returns true if the service returned a value for the KeyConditions property.
|
boolean |
hasQueryFilter()
For responses, this returns true if the service returned a value for the QueryFilter property.
|
String |
indexName()
The name of an index to query.
|
String |
keyConditionExpression()
The condition that specifies the key values for items to be retrieved by the
Query action. |
Map<String,Condition> |
keyConditions()
This is a legacy parameter.
|
Integer |
limit()
The maximum number of items to evaluate (not necessarily the number of matching items).
|
String |
projectionExpression()
A string that identifies one or more attributes to retrieve from the table.
|
Map<String,Condition> |
queryFilter()
This is a legacy parameter.
|
ReturnConsumedCapacity |
returnConsumedCapacity()
Returns the value of the ReturnConsumedCapacity property for this object.
|
String |
returnConsumedCapacityAsString()
Returns the value of the ReturnConsumedCapacity property for this object.
|
Boolean |
scanIndexForward()
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. |
List<SdkField<?>> |
sdkFields() |
Select |
select()
The attributes to be returned in the result.
|
String |
selectAsString()
The attributes to be returned in the result.
|
static Class<? extends QueryRequest.Builder> |
serializableBuilderClass() |
String |
tableName()
The name of the table containing the requested items.
|
QueryRequest.Builder |
toBuilder() |
String |
toString()
Returns a string representation of this object.
|
overrideConfiguration
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
copy
public final String tableName()
The name of the table containing the requested items.
public final String indexName()
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.
IndexName
parameter, you must also provide
TableName.
public final Select 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 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.
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
.)
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.
If the service returns an enum value that is not available in the current SDK version, select
will
return Select.UNKNOWN_TO_SDK_VERSION
. The raw value returned by the service is available from
selectAsString()
.
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.
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
.)
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.
Select
public final String selectAsString()
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.
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
.)
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.
If the service returns an enum value that is not available in the current SDK version, select
will
return Select.UNKNOWN_TO_SDK_VERSION
. The raw value returned by the service is available from
selectAsString()
.
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.
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
.)
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.
Select
public final boolean hasAttributesToGet()
isEmpty()
method on the property).
This is useful because the SDK will never return a null collection or map, but you may need to differentiate
between the service returning nothing (or null) and the service returning an empty collection or map. For
requests, this returns true if a value for the property was specified in the request builder, and false if a
value was not specified.public final List<String> attributesToGet()
This is a legacy parameter. Use ProjectionExpression
instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasAttributesToGet()
method.
ProjectionExpression
instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.public final Integer 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 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 in the Amazon DynamoDB Developer Guide.
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 in the Amazon DynamoDB Developer Guide.public final Boolean consistentRead()
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
.
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
.
public final boolean hasKeyConditions()
isEmpty()
method on the property).
This is useful because the SDK will never return a null collection or map, but you may need to differentiate
between the service returning nothing (or null) and the service returning an empty collection or map. For
requests, this returns true if a value for the property was specified in the request builder, and false if a
value was not specified.public final Map<String,Condition> keyConditions()
This is a legacy parameter. Use KeyConditionExpression
instead. For more information, see KeyConditions in the Amazon DynamoDB Developer Guide.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasKeyConditions()
method.
KeyConditionExpression
instead. For more information, see KeyConditions in the Amazon DynamoDB Developer Guide.public final boolean hasQueryFilter()
isEmpty()
method on the property).
This is useful because the SDK will never return a null collection or map, but you may need to differentiate
between the service returning nothing (or null) and the service returning an empty collection or map. For
requests, this returns true if a value for the property was specified in the request builder, and false if a
value was not specified.public final Map<String,Condition> queryFilter()
This is a legacy parameter. Use FilterExpression
instead. For more information, see QueryFilter in the Amazon DynamoDB Developer Guide.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasQueryFilter()
method.
FilterExpression
instead. For more information, see QueryFilter in the Amazon DynamoDB Developer Guide.public final ConditionalOperator conditionalOperator()
This is a legacy parameter. Use FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.
If the service returns an enum value that is not available in the current SDK version,
conditionalOperator
will return ConditionalOperator.UNKNOWN_TO_SDK_VERSION
. The raw value
returned by the service is available from conditionalOperatorAsString()
.
FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.ConditionalOperator
public final String conditionalOperatorAsString()
This is a legacy parameter. Use FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.
If the service returns an enum value that is not available in the current SDK version,
conditionalOperator
will return ConditionalOperator.UNKNOWN_TO_SDK_VERSION
. The raw value
returned by the service is available from conditionalOperatorAsString()
.
FilterExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.ConditionalOperator
public final Boolean scanIndexForward()
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.
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.
public final boolean hasExclusiveStartKey()
isEmpty()
method on the property).
This is useful because the SDK will never return a null collection or map, but you may need to differentiate
between the service returning nothing (or null) and the service returning an empty collection or map. For
requests, this returns true if a value for the property was specified in the request builder, and false if a
value was not specified.public final Map<String,AttributeValue> 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.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasExclusiveStartKey()
method.
LastEvaluatedKey
in the previous operation.
The data type for ExclusiveStartKey
must be String, Number, or Binary. No set data types are
allowed.
public final ReturnConsumedCapacity returnConsumedCapacity()
If the service returns an enum value that is not available in the current SDK version,
returnConsumedCapacity
will return ReturnConsumedCapacity.UNKNOWN_TO_SDK_VERSION
. The raw value
returned by the service is available from returnConsumedCapacityAsString()
.
ReturnConsumedCapacity
public final String returnConsumedCapacityAsString()
If the service returns an enum value that is not available in the current SDK version,
returnConsumedCapacity
will return ReturnConsumedCapacity.UNKNOWN_TO_SDK_VERSION
. The raw value
returned by the service is available from returnConsumedCapacityAsString()
.
ReturnConsumedCapacity
public final String projectionExpression()
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.
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.
public final String filterExpression()
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 in the Amazon DynamoDB Developer Guide.
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 in the Amazon DynamoDB Developer Guide.
public final String keyConditionExpression()
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 name begins_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 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.
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 name begins_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 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.
public final boolean hasExpressionAttributeNames()
isEmpty()
method on the
property). This is useful because the SDK will never return a null collection or map, but you may need to
differentiate between the service returning nothing (or null) and the service returning an empty collection or
map. For requests, this returns true if a value for the property was specified in the request builder, and false
if a value was not specified.public final Map<String,String> expressionAttributeNames()
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.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasExpressionAttributeNames()
method.
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.
public final boolean hasExpressionAttributeValues()
isEmpty()
method on the
property). This is useful because the SDK will never return a null collection or map, but you may need to
differentiate between the service returning nothing (or null) and the service returning an empty collection or
map. For requests, this returns true if a value for the property was specified in the request builder, and false
if a value was not specified.public final Map<String,AttributeValue> expressionAttributeValues()
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.
Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.
This method will never return null. If you would like to know whether the service returned this field (so that
you can differentiate between null and empty), you can use the hasExpressionAttributeValues()
method.
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.
public QueryRequest.Builder toBuilder()
toBuilder
in interface ToCopyableBuilder<QueryRequest.Builder,QueryRequest>
toBuilder
in class DynamoDbRequest
public static QueryRequest.Builder builder()
public static Class<? extends QueryRequest.Builder> serializableBuilderClass()
public final int hashCode()
hashCode
in class AwsRequest
public final boolean equals(Object obj)
equals
in class AwsRequest
public final boolean equalsBySdkFields(Object obj)
equalsBySdkFields
in interface SdkPojo
public final String toString()
public final <T> Optional<T> getValueForField(String fieldName, Class<T> clazz)
getValueForField
in class SdkRequest
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