org.apache.hadoop.hive.ql.optimizer
Class MapJoinProcessor
java.lang.Object
org.apache.hadoop.hive.ql.optimizer.MapJoinProcessor
- All Implemented Interfaces:
- Transform
public class MapJoinProcessor
- extends Object
- implements Transform
Implementation of one of the rule-based map join optimization. User passes hints to specify map-joins and during this optimization,
all user specified map joins are converted to MapJoins - the reduce sink operator above the join are converted to map sink operators.
In future, once statistics are implemented, this transformation can also be done based on costs.
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
MapJoinProcessor
public MapJoinProcessor()
- empty constructor
transform
public ParseContext transform(ParseContext pactx)
throws SemanticException
- Transform the query tree. For each join, check if it is a map-side join (user specified). If yes,
convert it to a map-side join.
- Specified by:
transform
in interface Transform
- Parameters:
pactx
- current parse context
- Returns:
- ParseContext
- Throws:
SemanticException
getMapJoinFS
public static NodeProcessor getMapJoinFS()
getMapJoinDefault
public static NodeProcessor getMapJoinDefault()
getDefault
public static NodeProcessor getDefault()
getCurrentMapJoin
public static NodeProcessor getCurrentMapJoin()
Copyright © 2009 The Apache Software Foundation