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DDB Enhanced: Added support for projection expression #1756

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Apr 6, 2020
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DDB Enhanced: Added support for projection expression #1756

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6 changes: 6 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
# __2.11.10__

## __Amazon DynamoDB Enhanced Client [Preview]__
- ### Features
- The enhanced DDB query and scan request now supports projections.

# __2.11.9__ __2020-04-03__
## __AWS RoboMaker__
- ### Features
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24 changes: 23 additions & 1 deletion ...ain/java/software/amazon/awssdk/enhanced/dynamodb/internal/operations/QueryOperation.java
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Expand Up @@ -15,8 +15,14 @@

package software.amazon.awssdk.enhanced.dynamodb.internal.operations;

import static software.amazon.awssdk.enhanced.dynamodb.internal.EnhancedClientUtils.cleanAttributeName;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.UnaryOperator;
import software.amazon.awssdk.annotations.SdkInternalApi;
import software.amazon.awssdk.core.async.SdkPublisher;
import software.amazon.awssdk.core.pagination.sync.SdkIterable;
Expand All @@ -37,6 +43,8 @@
public class QueryOperation<T> implements PaginatedTableOperation<T, QueryRequest, QueryResponse>,
PaginatedIndexOperation<T, QueryRequest, QueryResponse> {

private static final UnaryOperator<String> PROJECTION_EXPRESSION_KEY_MAPPER = k -> "#AMZN_MAPPED_" + cleanAttributeName(k);

private final QueryEnhancedRequest request;

private QueryOperation(QueryEnhancedRequest request) {
Expand All @@ -60,6 +68,19 @@ public QueryRequest generateRequest(TableSchema<T> tableSchema,
expressionNames = Expression.joinNames(expressionNames, this.request.filterExpression().expressionNames());
}

String projectionExpression = null;
if (this.request.attributesToProject() != null) {
List<String> placeholders = new ArrayList<>();
Map<String, String> projectionPlaceholders = new HashMap<>();
this.request.attributesToProject().forEach(attr -> {
String placeholder = PROJECTION_EXPRESSION_KEY_MAPPER.apply(attr);
placeholders.add(placeholder);
projectionPlaceholders.put(placeholder, attr);
});
projectionExpression = String.join(",", placeholders);
expressionNames = Expression.joinNames(expressionNames, projectionPlaceholders);
}

QueryRequest.Builder queryRequest = QueryRequest.builder()
.tableName(operationContext.tableName())
.keyConditionExpression(queryExpression.expression())
Expand All @@ -68,7 +89,8 @@ public QueryRequest generateRequest(TableSchema<T> tableSchema,
.scanIndexForward(this.request.scanIndexForward())
.limit(this.request.limit())
.exclusiveStartKey(this.request.exclusiveStartKey())
.consistentRead(this.request.consistentRead());
.consistentRead(this.request.consistentRead())
.projectionExpression(projectionExpression);

if (!TableMetadata.primaryIndexName().equals(operationContext.indexName())) {
queryRequest = queryRequest.indexName(operationContext.indexName());
Expand Down
41 changes: 37 additions & 4 deletions ...main/java/software/amazon/awssdk/enhanced/dynamodb/internal/operations/ScanOperation.java
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Expand Up @@ -15,25 +15,36 @@

package software.amazon.awssdk.enhanced.dynamodb.internal.operations;

import static software.amazon.awssdk.enhanced.dynamodb.internal.EnhancedClientUtils.cleanAttributeName;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.UnaryOperator;
import software.amazon.awssdk.annotations.SdkInternalApi;
import software.amazon.awssdk.core.async.SdkPublisher;
import software.amazon.awssdk.core.pagination.sync.SdkIterable;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClientExtension;
import software.amazon.awssdk.enhanced.dynamodb.Expression;
import software.amazon.awssdk.enhanced.dynamodb.TableMetadata;
import software.amazon.awssdk.enhanced.dynamodb.TableSchema;
import software.amazon.awssdk.enhanced.dynamodb.internal.EnhancedClientUtils;
import software.amazon.awssdk.enhanced.dynamodb.model.Page;
import software.amazon.awssdk.enhanced.dynamodb.model.ScanEnhancedRequest;
import software.amazon.awssdk.services.dynamodb.DynamoDbAsyncClient;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.ScanRequest;
import software.amazon.awssdk.services.dynamodb.model.ScanResponse;

@SdkInternalApi
public class ScanOperation<T> implements PaginatedTableOperation<T, ScanRequest, ScanResponse>,
PaginatedIndexOperation<T, ScanRequest, ScanResponse> {

private static final UnaryOperator<String> PROJECTION_EXPRESSION_KEY_MAPPER = k -> "#AMZN_MAPPED_" + cleanAttributeName(k);

private final ScanEnhancedRequest request;

private ScanOperation(ScanEnhancedRequest request) {
Expand All @@ -48,20 +59,42 @@ public static <T> ScanOperation<T> create(ScanEnhancedRequest request) {
public ScanRequest generateRequest(TableSchema<T> tableSchema,
OperationContext operationContext,
DynamoDbEnhancedClientExtension extension) {
Map<String, AttributeValue> expressionValues = null;
Map<String, String> expressionNames = null;

if (this.request.filterExpression() != null) {
expressionValues = this.request.filterExpression().expressionValues();
expressionNames = this.request.filterExpression().expressionNames();
}

String projectionExpression = null;
if (this.request.attributesToProject() != null) {
List<String> placeholders = new ArrayList<>();
Map<String, String> projectionPlaceholders = new HashMap<>();
this.request.attributesToProject().forEach(attr -> {
String placeholder = PROJECTION_EXPRESSION_KEY_MAPPER.apply(attr);
placeholders.add(placeholder);
projectionPlaceholders.put(placeholder, attr);
});
projectionExpression = String.join(",", placeholders);
expressionNames = Expression.joinNames(expressionNames, projectionPlaceholders);
}

ScanRequest.Builder scanRequest = ScanRequest.builder()
.tableName(operationContext.tableName())
.limit(this.request.limit())
.exclusiveStartKey(this.request.exclusiveStartKey())
.consistentRead(this.request.consistentRead());
.consistentRead(this.request.consistentRead())
.expressionAttributeValues(expressionValues)
.expressionAttributeNames(expressionNames)
.projectionExpression(projectionExpression);

if (!TableMetadata.primaryIndexName().equals(operationContext.indexName())) {
scanRequest = scanRequest.indexName(operationContext.indexName());
}

if (this.request.filterExpression() != null) {
scanRequest = scanRequest.filterExpression(this.request.filterExpression().expression())
.expressionAttributeValues(this.request.filterExpression().expressionValues())
.expressionAttributeNames(this.request.filterExpression().expressionNames());
scanRequest = scanRequest.filterExpression(this.request.filterExpression().expression());
}

return scanRequest.build();
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94 changes: 93 additions & 1 deletion ...ed/src/main/java/software/amazon/awssdk/enhanced/dynamodb/model/QueryEnhancedRequest.java
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Expand Up @@ -15,7 +15,12 @@

package software.amazon.awssdk.enhanced.dynamodb.model;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import software.amazon.awssdk.annotations.SdkPublicApi;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbAsyncIndex;
Expand All @@ -41,6 +46,7 @@ public final class QueryEnhancedRequest {
private final Integer limit;
private final Boolean consistentRead;
private final Expression filterExpression;
private final List<String> attributesToProject;

private QueryEnhancedRequest(Builder builder) {
this.queryConditional = builder.queryConditional;
Expand All @@ -49,6 +55,9 @@ private QueryEnhancedRequest(Builder builder) {
this.limit = builder.limit;
this.consistentRead = builder.consistentRead;
this.filterExpression = builder.filterExpression;
this.attributesToProject = builder.attributesToProject != null
? Collections.unmodifiableList(builder.attributesToProject)
: null;
}

/**
Expand All @@ -67,7 +76,8 @@ public Builder toBuilder() {
.scanIndexForward(scanIndexForward)
.limit(limit)
.consistentRead(consistentRead)
.filterExpression(filterExpression);
.filterExpression(filterExpression)
.attributesToProject(attributesToProject);
}

/**
Expand Down Expand Up @@ -113,6 +123,13 @@ public Expression filterExpression() {
return filterExpression;
}

/**
* Returns the list of projected attributes on this request object, or an null if no projection is specified.
*/
public List<String> attributesToProject() {
return attributesToProject;
}

@Override
public boolean equals(Object o) {
if (this == o) {
Expand Down Expand Up @@ -142,6 +159,12 @@ public boolean equals(Object o) {
if (consistentRead != null ? ! consistentRead.equals(query.consistentRead) : query.consistentRead != null) {
return false;
}
if (attributesToProject != null
? ! attributesToProject.equals(query.attributesToProject)
: query.attributesToProject != null
) {
return false;
}
return filterExpression != null ? filterExpression.equals(query.filterExpression) : query.filterExpression == null;
}

Expand All @@ -153,6 +176,7 @@ public int hashCode() {
result = 31 * result + (limit != null ? limit.hashCode() : 0);
result = 31 * result + (consistentRead != null ? consistentRead.hashCode() : 0);
result = 31 * result + (filterExpression != null ? filterExpression.hashCode() : 0);
result = 31 * result + (attributesToProject != null ? attributesToProject.hashCode() : 0);
return result;
}

Expand All @@ -168,6 +192,7 @@ public static final class Builder {
private Integer limit;
private Boolean consistentRead;
private Expression filterExpression;
private List<String> attributesToProject;

private Builder() {
}
Expand Down Expand Up @@ -255,6 +280,73 @@ public Builder filterExpression(Expression filterExpression) {
return this;
}

/**
* <p>
* Sets a collection of the attribute names to be retrieved from the database. These attributes can include
* scalars, sets, or elements of a JSON document.
* </p>
* <p>
* 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.
* </p>
* <p>
* For more information, see <a href=
* "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
* >Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
* </p>
* @param attributesToProject
* A collection of the attributes names to be retrieved from the database.
* @return Returns a reference to this object so that method calls can be chained together.
*/
public Builder attributesToProject(Collection<String> attributesToProject) {
this.attributesToProject = attributesToProject != null ? new ArrayList<>(attributesToProject) : null;
return this;
}

/**
* <p>
* Sets one or more attribute names to be retrieved from the database. These attributes can include
* scalars, sets, or elements of a JSON document.
* </p>
* <p>
* 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.
* </p>
* <p>
* For more information, see <a href=
* "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
* >Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
* </p>
* @param attributesToProject
* One or more attributes names to be retrieved from the database.
* @return Returns a reference to this object so that method calls can be chained together.
*/
public Builder attributesToProject(String... attributesToProject) {
return attributesToProject(Arrays.asList(attributesToProject));
}

/**
* <p>
* Adds a single attribute name to be retrieved from the database. This attribute can include
* scalars, sets, or elements of a JSON document.
* </p>
* <p>
* For more information, see <a href=
* "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
* >Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
* </p>
* @param attributeToProject
* An additional single attribute name to be retrieved from the database.
* @return Returns a reference to this object so that method calls can be chained together.
*/
public Builder addAttributeToProject(String attributeToProject) {
if (attributesToProject == null) {
attributesToProject = new ArrayList<>();
}
attributesToProject.add(attributeToProject);
return this;
}

public QueryEnhancedRequest build() {
return new QueryEnhancedRequest(this);
}
Expand Down
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