org.apache.calcite.sql2rel

Class CorrelateProjectExtractor

java.lang.Object

org.apache.calcite.rel.RelShuttleImpl

org.apache.calcite.rel.RelHomogeneousShuttle

org.apache.calcite.sql2rel.CorrelateProjectExtractor

All Implemented Interfaces:

RelShuttle

@API(since="1.27",
     status=EXPERIMENTAL)
public final class CorrelateProjectExtractor
extends RelHomogeneousShuttle

A visitor for relational expressions that extracts a Project, with a "simple" computation over the correlated variables, from the right side of a correlation (Correlate) and places it on the left side.

Plan before

 LogicalCorrelate(correlation=[$cor0], joinType=[left], requiredColumns=[{7}])
   LogicalTableScan(table=[[scott, EMP]])
   LogicalFilter(condition=[=($0, +(10, $cor0.DEPTNO))])
     LogicalTableScan(table=[[scott, DEPT]])
 

Plan after

 LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3],... DNAME=[$10], LOC=[$11])
   LogicalCorrelate(correlation=[$cor0], joinType=[left], requiredColumns=[{8}])
     LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], ... COMM=[$6], DEPTNO=[$7], $f8=[+(10, $7)])
       LogicalTableScan(table=[[scott, EMP]])
     LogicalFilter(condition=[=($0, $cor0.$f8)])
       LogicalTableScan(table=[[scott, DEPT]])
 

Essentially this transformation moves the computation over a correlated expression from the inner loop to the outer loop. It materializes the computation on the left side and flattens expressions on correlated variables on the right side.

Field Summary

Fields inherited from class org.apache.calcite.rel.RelShuttleImpl

stack

Constructor Summary

Constructors

Constructor and Description
CorrelateProjectExtractor(RelBuilderFactory factory)

Method Summary

Modifier and Type	Method and Description
RelNode	visit(LogicalCorrelate correlate)

Methods inherited from class org.apache.calcite.rel.RelHomogeneousShuttle

visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class org.apache.calcite.rel.RelShuttleImpl

visit, visitChild, visitChildren

Methods inherited from class java.lang.Object

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

Constructor Detail

CorrelateProjectExtractor

public CorrelateProjectExtractor(RelBuilderFactory factory)

Method Detail

visit

public RelNode visit(LogicalCorrelate correlate)

Specified by:

visit in interface RelShuttle

Overrides:

visit in class RelHomogeneousShuttle