io.prestosql.sql.planner.optimizations

Class ImplementIntersectAndExceptAsUnion

java.lang.Object

io.prestosql.sql.planner.optimizations.ImplementIntersectAndExceptAsUnion

All Implemented Interfaces:

PlanOptimizer

public class ImplementIntersectAndExceptAsUnion
extends Object
implements PlanOptimizer

Converts INTERSECT and EXCEPT queries into UNION ALL..GROUP BY...WHERE Eg: SELECT a FROM foo INTERSECT SELECT x FROM bar

=>

SELECT a FROM (SELECT a, COUNT(foo_marker) AS foo_cnt, COUNT(bar_marker) AS bar_cnt FROM ( SELECT a, true as foo_marker, null as bar_marker FROM foo UNION ALL SELECT x, null as foo_marker, true as bar_marker FROM bar ) T1 GROUP BY a) T2 WHERE foo_cnt >= 1 AND bar_cnt >= 1;

Eg: SELECT a FROM foo EXCEPT SELECT x FROM bar

=>

SELECT a FROM (SELECT a, COUNT(foo_marker) AS foo_cnt, COUNT(bar_marker) AS bar_cnt FROM ( SELECT a, true as foo_marker, null as bar_marker FROM foo UNION ALL SELECT x, null as foo_marker, true as bar_marker FROM bar ) T1 GROUP BY a) T2 WHERE foo_cnt >= 1 AND bar_cnt = 0;

Constructor Summary

Constructors

Constructor and Description
ImplementIntersectAndExceptAsUnion()

Method Summary

Modifier and Type	Method and Description
PlanNode	optimize(PlanNode plan, Session session, TypeProvider types, SymbolAllocator symbolAllocator, PlanNodeIdAllocator idAllocator, WarningCollector warningCollector)

Methods inherited from class java.lang.Object

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

Constructor Detail

ImplementIntersectAndExceptAsUnion

public ImplementIntersectAndExceptAsUnion()

Method Detail

optimize

public PlanNode optimize(PlanNode plan,
                         Session session,
                         TypeProvider types,
                         SymbolAllocator symbolAllocator,
                         PlanNodeIdAllocator idAllocator,
                         WarningCollector warningCollector)

Specified by:

optimize in interface PlanOptimizer