org.apache.hadoop.hive.ql.optimizer.unionproc
Class UnionProcessor
java.lang.Object
org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcessor
- All Implemented Interfaces:
- Transform
public class UnionProcessor
- extends Object
- implements 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.
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
UnionProcessor
public UnionProcessor()
- empty constructor
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 interface Transform
- Parameters:
pCtx
- the current parse context
- Returns:
- ParseContext
- Throws:
SemanticException
Copyright © 2009 The Apache Software Foundation