com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBScanExpression Maven / Gradle / Ivy
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/*
* Copyright 2011-2014 Amazon Technologies, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://aws.amazon.com/apache2.0
*
* This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
* OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and
* limitations under the License.
*/
package com.amazonaws.services.dynamodbv2.datamodeling;
import java.util.HashMap;
import java.util.Map;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.ComparisonOperator;
import com.amazonaws.services.dynamodbv2.model.Condition;
/**
* Options for filtering results from a scan operation. For example, callers can
* specify filter conditions so that only objects whose attributes match
* different conditions are returned (see {@link ComparisonOperator} for more
* information on the available comparison types).
*
* @see DynamoDBMapper#scan(Class, DynamoDBScanExpression)
*/
public class DynamoDBScanExpression {
/** Optional filter to limit the results of the scan. */
private Map scanFilter;
/** The exclusive start key for this scan. */
private Map exclusiveStartKey;
/** The limit of items to scan during this scan. */
private Integer limit;
/**
* The total number of segments into which the scan will be divided.
* Only required for parallel scan operation.
*/
private Integer totalSegments;
/**
* The ID (zero-based) of the segment to be scanned.
* Only required for parallel scan operation.
*/
private Integer segment;
/**
* Sets the scan filter to the map of attribute names to conditions given.
*
* @param scanFilter
* The map of attribute names to conditions to use when filtering
* scan results.
*/
public void setScanFilter(Map scanFilter) {
this.scanFilter = scanFilter;
}
/**
* Returns the scan filter as a map of attribute names to conditions.
*
* @return The scan filter as a map of attribute names to conditions.
*/
public Map getScanFilter() {
return scanFilter;
}
/**
* Adds a new filter condition to the current scan filter.
*
* @param attributeName
* The name of the attribute on which the specified condition
* operates.
* @param condition
* The condition which describes how the specified attribute is
* compared and if a row of data is included in the results
* returned by the scan operation.
*/
public void addFilterCondition(String attributeName, Condition condition) {
if ( scanFilter == null )
scanFilter = new HashMap();
scanFilter.put(attributeName, condition);
}
/**
* Returns the exclusive start key for this scan.
*/
public Map getExclusiveStartKey() {
return exclusiveStartKey;
}
/**
* Sets the exclusive start key for this scan.
*/
public void setExclusiveStartKey(Map exclusiveStartKey) {
this.exclusiveStartKey = exclusiveStartKey;
}
/**
* Sets the exclusive start key for this scan and returns a pointer to this
* object for method-chaining.
*/
public DynamoDBScanExpression withExclusiveStartKey(Map exclusiveStartKey) {
this.exclusiveStartKey = exclusiveStartKey;
return this;
}
/**
* Returns the limit of items to scan during this scan.
*
* Use with caution. Please note that this is not the same as the
* number of items to return from the scan operation -- the operation will
* cease and return as soon as this many items are scanned, even if no
* matching results are found. Furthermore, {@link PaginatedScanList} will
* execute as many scan operations as necessary until it either reaches the
* end of the result set as indicated by DynamoDB or enough elements are
* available to fulfill the list operation (e.g. iteration). Therefore,
* except when scanning without a scan filter, it's usually bad practice to
* set a low limit, since doing so will often generate the same amount of
* traffic to DynamoDB but with a greater number of round trips and
* therefore more overall latency.
*/
public Integer getLimit() {
return limit;
}
/**
* Sets the limit of items to scan during this scan. Please note that this
* is not the same as the number of items to return from the scan
* operation -- the operation will cease and return as soon as this many
* items are scanned, even if no matching results are found.
*
* @see DynamoDBScanExpression#getLimit()
*/
public void setLimit(Integer limit) {
this.limit = limit;
}
/**
* Sets the limit of items to scan and returns a pointer to this object for
* method-chaining. Please note that this is not the same as the
* number of items to return from the scan operation -- the operation will
* cease and return as soon as this many items are scanned, even if no
* matching results are found.
*
* @see DynamoDBScanExpression#getLimit()
*/
public DynamoDBScanExpression withLimit(Integer limit) {
this.limit = limit;
return this;
}
/**
* Returns the total number of segments into which the scan will be divided.
*/
public Integer getTotalSegments() {
return totalSegments;
}
/**
* Sets the total number of segments into which the scan will be divided.
*/
public void setTotalSegments(Integer totalSegments) {
this.totalSegments = totalSegments;
}
/**
* Sets the total number of segments into which the scan will be divided and
* returns a pointer to this object for method-chaining.
*/
public DynamoDBScanExpression withTotalSegments(Integer totalSegments) {
setTotalSegments(totalSegments);
return this;
}
/**
* Returns the ID of the segment to be scanned.
*/
public Integer getSegment() {
return segment;
}
/**
* Sets the ID of the segment to be scanned.
*/
public void setSegment(Integer segment) {
this.segment = segment;
}
/**
* Sets the ID of the segment to be scanned and returns a pointer to this
* object for method-chaining.
*/
public DynamoDBScanExpression withSegment(Integer segment) {
setSegment(segment);
return this;
}
}