com.allanbank.mongodb.builder

Class Aggregate

java.lang.Object

com.allanbank.mongodb.builder.Aggregate

public class Aggregate
extends Object

Aggregate provides support for the aggregate command supporting a pipeline of commands to execute.

Instances of this class are constructed via the inner Aggregate.Builder class. Due to the potential complexity of pipelines and the associated operators the Builder is intended to be used with the various support classes including the Expressions library. For example:

 
  import static com.allanbank.mongodb.builder.AggregationGroupField.set;
  import static com.allanbank.mongodb.builder.AggregationGroupId.id;
  import static com.allanbank.mongodb.builder.AggregationProjectFields.includeWithoutId;
  import static com.allanbank.mongodb.builder.QueryBuilder.where;
  import static com.allanbank.mongodb.builder.Sort.asc;
  import static com.allanbank.mongodb.builder.Sort.desc;
  import static com.allanbank.mongodb.builder.expression.Expressions.field;
  import static com.allanbank.mongodb.builder.expression.Expressions.set;
 
  DocumentBuilder b1 = BuilderFactory.start();
  DocumentBuilder b2 = BuilderFactory.start();
  Aggregate.Builder builder = new Aggregate.Builder();
 
  builder.match(where("state").notEqualTo("NZ"))
          .group(id().addField("state")
                     .addField("city"),
                 set("pop").sum("pop"))
          .sort(asc("pop"))
          .group(id("_id.state"),
                 set("biggestcity").last("_id.city"),
                 set("biggestpop").last("pop"),
                 set("smallestcity").first("_id.city"),
                 set("smallestpop").first("pop"))
          .project(
                  includeWithoutId(),
                  set("state", field("_id")),
                  set("biggestCity",
                          b1.add(set("name", field("biggestcity"))).add(
                                  set("pop", field("biggestpop")))),
                  set("smallestCity",
                          b2.add(set("name", field("smallestcity"))).add(
                                  set("pop", field("smallestpop")))))
          .sort(desc("biggestCity.pop"));
 
 

See Also:

Example Inspired By

API Notice:

This class is part of the driver's API. Public and protected members will be deprecated for at least 1 non-bugfix release (version numbers are <major>.<minor>.<bugfix>) before being removed or modified.

Copyright ©:

2012-2013, Allanbank Consulting, Inc., All Rights Reserved

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Aggregate.Builder Builder provides the ability to construct aggregate command pipelines.

Field Summary

Fields

Modifier and Type	Field and Description
static Version	ALLOW_DISK_USAGE_REQUIRED_VERSION The first version of MongoDB to support the $geoNear pipeline operator.
static Version	CURSOR_VERSION The first version of MongoDB to support the aggregate command using a cursor.
static Version	EXPLAIN_VERSION The first version of MongoDB to support the aggregate command with the explain option.
static Version	GEO_NEAR_REQUIRED_VERSION The first version of MongoDB to support the $geoNear pipeline operator.
static Version	MAX_TIMEOUT_VERSION The first version of MongoDB to support the aggregate command with the ability to limit the execution time on the server.
static Version	REDACT_REQUIRED_VERSION The first version of MongoDB to support the $redact pipeline operator.
static Version	REQUIRED_VERSION The first version of MongoDB to support the aggregate command.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Aggregate(Aggregate.Builder builder) Creates a new Aggregation.

Method Summary

Methods

Modifier and Type	Method and Description
static Aggregate.Builder	builder() Creates a new builder for a Aggregate.
int	getBatchSize() Returns the number of documents to be returned in each batch of results by the cursor.
int	getCursorLimit() Returns the total number of documents to be returned by the cursor.
long	getMaximumTimeMilliseconds() Returns the maximum amount of time to allow the command to run on the Server before it is aborted.
List<Element>	getPipeline() Returns the pipeline of operations to apply.
ReadPreference	getReadPreference() Returns the ReadPreference specifying which servers may be used to execute the aggregation.
Version	getRequiredVersion() Returns the version required for the aggregation.
boolean	isAllowDiskUsage() Returns true if the aggregation results should be allowed to spill to disk.
boolean	isUseCursor() Returns true if the aggregation results should be returned as a cursor.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ALLOW_DISK_USAGE_REQUIRED_VERSION

public static final Version ALLOW_DISK_USAGE_REQUIRED_VERSION

The first version of MongoDB to support the $geoNear pipeline operator.

CURSOR_VERSION

public static final Version CURSOR_VERSION

The first version of MongoDB to support the aggregate command using a cursor.

EXPLAIN_VERSION

public static final Version EXPLAIN_VERSION

The first version of MongoDB to support the aggregate command with the explain option.

GEO_NEAR_REQUIRED_VERSION

public static final Version GEO_NEAR_REQUIRED_VERSION

The first version of MongoDB to support the $geoNear pipeline operator.

MAX_TIMEOUT_VERSION

public static final Version MAX_TIMEOUT_VERSION

The first version of MongoDB to support the aggregate command with the ability to limit the execution time on the server.

REDACT_REQUIRED_VERSION

public static final Version REDACT_REQUIRED_VERSION

The first version of MongoDB to support the $redact pipeline operator.

REQUIRED_VERSION

public static final Version REQUIRED_VERSION

The first version of MongoDB to support the aggregate command.

Constructor Detail

Aggregate

protected Aggregate(Aggregate.Builder builder)

Creates a new Aggregation.

Parameters:

builder - The builder for the Aggregation instance.

Method Detail

builder

public static Aggregate.Builder builder()

Creates a new builder for a Aggregate.

Returns:

The builder to construct a Aggregate.

getBatchSize

public int getBatchSize()

Returns the number of documents to be returned in each batch of results by the cursor.

Returns:

The number of documents to be returned in each batch of results by the cursor.

getCursorLimit

public int getCursorLimit()

Returns the total number of documents to be returned by the cursor.

Returns:

The total number of documents to be returned the cursor.

getMaximumTimeMilliseconds

public long getMaximumTimeMilliseconds()

Returns the maximum amount of time to allow the command to run on the Server before it is aborted.

Returns:

The maximum amount of time to allow the command to run on the Server before it is aborted.

Since:

MongoDB 2.6

getPipeline

public List<Element> getPipeline()

Returns the pipeline of operations to apply.

Returns:

The pipeline of operations to apply.

getReadPreference

public ReadPreference getReadPreference()

Returns the ReadPreference specifying which servers may be used to execute the aggregation.

If null then the MongoCollection instance's ReadPreference will be used.

Returns:

The read preference to use.

See Also:

MongoCollection.getReadPreference()

getRequiredVersion

public Version getRequiredVersion()

Returns the version required for the aggregation.

Returns:

The version required for the aggregation.

isAllowDiskUsage

public boolean isAllowDiskUsage()

Returns true if the aggregation results should be allowed to spill to disk.

Returns:

True if the aggregation results should be allowed to spill to disk.

isUseCursor

public boolean isUseCursor()

Returns true if the aggregation results should be returned as a cursor.

Returns:

True if the aggregation results should be returned as a cursor.