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 java.lang.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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MapJoinProcessor.CurrentMapJoin CurrentMapJoin.
static class	MapJoinProcessor.Default Default.
static class	MapJoinProcessor.MapJoinDefault MapJoinDefault.
static class	MapJoinProcessor.MapJoinFS MapJoinFS.
static class	MapJoinProcessor.MapJoinWalkerCtx MapJoinWalkerCtx.

Constructor Summary

Constructors

Constructor and Description
MapJoinProcessor() empty constructor.

Method Summary

Modifier and Type	Method and Description
static int	checkMapJoin(int mapJoinPos, JoinCondDesc[] condns)
static MapJoinOperator	convertMapJoin(java.util.LinkedHashMap<Operator<? extends OperatorDesc>,OpParseContext> opParseCtxMap, JoinOperator op, QBJoinTree joinTree, int mapJoinPos, boolean noCheckOuterJoin, boolean validateMapJoinTree) convert a regular join to a a map-side join.
static MapJoinOperator	convertSMBJoinToMapJoin(java.util.Map<Operator<? extends OperatorDesc>,OpParseContext> opParseCtxMap, SMBMapJoinOperator smbJoinOp, QBJoinTree joinTree, int bigTablePos, boolean noCheckOuterJoin) convert a sortmerge join to a a map-side join.
MapJoinOperator	generateMapJoinOperator(ParseContext pctx, JoinOperator op, QBJoinTree joinTree, int mapJoinPos)
static java.lang.String	genLocalWorkForMapJoin(MapredWork newWork, MapJoinOperator newMapJoinOp, int mapJoinPos)
static java.lang.String	genMapJoinOpAndLocalWork(MapredWork newWork, JoinOperator op, int mapJoinPos) Convert the join to a map-join and also generate any local work needed.
static java.util.Set<java.lang.Integer>	getBigTableCandidates(JoinCondDesc[] condns) Get a list of big table candidates.
static NodeProcessor	getCurrentMapJoin()
static NodeProcessor	getDefault()
static NodeProcessor	getMapJoinDefault()
static NodeProcessor	getMapJoinFS()
ParseContext	transform(ParseContext pactx) Transform the query tree.

Methods inherited from class java.lang.Object

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

Constructor Detail

MapJoinProcessor

public MapJoinProcessor()

empty constructor.

Method Detail

genMapJoinOpAndLocalWork

public static java.lang.String genMapJoinOpAndLocalWork(MapredWork newWork,
                                                        JoinOperator op,
                                                        int mapJoinPos)
                                                 throws SemanticException

Convert the join to a map-join and also generate any local work needed.

Parameters:

newWork - MapredWork in which the conversion is to happen

op - The join operator that needs to be converted to map-join

bigTablePos -

Returns:

the alias to the big table

Throws:

SemanticException

genLocalWorkForMapJoin

public static java.lang.String genLocalWorkForMapJoin(MapredWork newWork,
                                                      MapJoinOperator newMapJoinOp,
                                                      int mapJoinPos)
                                               throws SemanticException

Throws:

SemanticException

convertMapJoin

public static MapJoinOperator convertMapJoin(java.util.LinkedHashMap<Operator<? extends OperatorDesc>,OpParseContext> opParseCtxMap,
                                             JoinOperator op,
                                             QBJoinTree joinTree,
                                             int mapJoinPos,
                                             boolean noCheckOuterJoin,
                                             boolean validateMapJoinTree)
                                      throws SemanticException

convert a regular join to a a map-side join.

Parameters:

opParseCtxMap -

op - join operator

joinTree - qb join tree

mapJoinPos - position of the source to be read as part of map-reduce framework. All other sources are cached in memory

noCheckOuterJoin -

Throws:

SemanticException

convertSMBJoinToMapJoin

public static MapJoinOperator convertSMBJoinToMapJoin(java.util.Map<Operator<? extends OperatorDesc>,OpParseContext> opParseCtxMap,
                                                      SMBMapJoinOperator smbJoinOp,
                                                      QBJoinTree joinTree,
                                                      int bigTablePos,
                                                      boolean noCheckOuterJoin)
                                               throws SemanticException

convert a sortmerge join to a a map-side join.

Parameters:

opParseCtxMap -

smbJoinOp - join operator

joinTree - qb join tree

bigTablePos - position of the source to be read as part of map-reduce framework. All other sources are cached in memory

noCheckOuterJoin -

Throws:

SemanticException

generateMapJoinOperator

public MapJoinOperator generateMapJoinOperator(ParseContext pctx,
                                               JoinOperator op,
                                               QBJoinTree joinTree,
                                               int mapJoinPos)
                                        throws SemanticException

Throws:

SemanticException

getBigTableCandidates

public static java.util.Set<java.lang.Integer> getBigTableCandidates(JoinCondDesc[] condns)

Get a list of big table candidates. Only the tables in the returned set can be used as big table in the join operation. The logic here is to scan the join condition array from left to right. If see a inner join, and the bigTableCandidates is empty or the outer join that we last saw is a right outer join, add both side of this inner join to big table candidates only if they are not in bad position. If see a left outer join, set lastSeenRightOuterJoin to false, and the bigTableCandidates is empty, add the left side to it, and if the bigTableCandidates is not empty, do nothing (which means the bigTableCandidates is from left side). If see a right outer join, set lastSeenRightOuterJoin to true, clear the bigTableCandidates, and add right side to the bigTableCandidates, it means the right side of a right outer join always win. If see a full outer join, return null immediately (no one can be the big table, can not do a mapjoin).

Parameters:

condns -

Returns:

set of big table candidates

checkMapJoin

public static int checkMapJoin(int mapJoinPos,
                               JoinCondDesc[] condns)

Parameters:

mapJoinPos - the position of big table as determined by either hints or auto conversion.

condns - the join conditions

Returns:

if given mapjoin position is a feasible big table position return same else -1.

Throws:

SemanticException - if given position is not in the big table candidates.

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()