org.apache.hadoop.hive.ql.optimizer.unionproc

Class UnionProcessor

java.lang.Object

org.apache.hadoop.hive.ql.optimizer.Transform

org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcessor

public class UnionProcessor
extends Transform

Implementation of the union processor. This can be enhanced later on. Currently, it does the following: Identify if both the subqueries of UNION are map-only. Store that fact in the unionDesc/UnionOperator. If either of the sub-query involves a map-reduce job, a FS is introduced on top of the UNION. This can be later optimized to clone all the operators above the UNION. The parse Context is not changed.

Constructor Summary

Constructors

Constructor and Description
UnionProcessor() empty constructor.

Method Summary

Modifier and Type	Method and Description
ParseContext	transform(ParseContext pCtx) Transform the query tree.

Methods inherited from class org.apache.hadoop.hive.ql.optimizer.Transform

beginPerfLogging, endPerfLogging, endPerfLogging

Methods inherited from class java.lang.Object

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

Constructor Detail

UnionProcessor

public UnionProcessor()

empty constructor.

Method Detail

transform

public ParseContext transform(ParseContext pCtx)
                       throws SemanticException

Transform the query tree. For each union, store the fact whether both the sub-queries are map-only

Specified by:

transform in class Transform

Parameters:

pCtx - the current parse context

Returns:

ParseContext

Throws:

SemanticException