// implement RelOptRule
public void onMatch(RelOptRuleCall call) {
ProjectRel origProj = call.rel(0);
JoinRel joinRel = call.rel(1);
// locate all fields referenced in the projection and join condition;
// determine which inputs are referenced in the projection and
// join condition; if all fields are being referenced and there are no
// special expressions, no point in proceeding any further
PushProjector pushProject =
new PushProjector(origProj, joinRel.getCondition(), joinRel, preserveExprCondition);
if (pushProject.locateAllRefs()) {
return;
}
// create left and right projections, projecting only those
// fields referenced on each side
RelNode leftProjRel = pushProject.createProjectRefsAndExprs(joinRel.getLeft(), true, false);
RelNode rightProjRel = pushProject.createProjectRefsAndExprs(joinRel.getRight(), true, true);
// convert the join condition to reference the projected columns
RexNode newJoinFilter = null;
int[] adjustments = pushProject.getAdjustments();
if (joinRel.getCondition() != null) {
List<RelDataTypeField> projJoinFieldList = new ArrayList<RelDataTypeField>();
projJoinFieldList.addAll(joinRel.getSystemFieldList());
projJoinFieldList.addAll(leftProjRel.getRowType().getFieldList());
projJoinFieldList.addAll(rightProjRel.getRowType().getFieldList());
newJoinFilter =
pushProject.convertRefsAndExprs(joinRel.getCondition(), projJoinFieldList, adjustments);
}
// create a new joinrel with the projected children
JoinRel newJoinRel =
new JoinRel(
joinRel.getCluster(),
leftProjRel,
rightProjRel,
newJoinFilter,
joinRel.getJoinType(),
Collections.<String>emptySet(),
joinRel.isSemiJoinDone(),
joinRel.getSystemFieldList());
// put the original project on top of the join, converting it to
// reference the modified projection list
ProjectRel topProject = pushProject.createNewProject(newJoinRel, adjustments);
call.transformTo(topProject);
}
public void onMatch(RelOptRuleCall call) {
JoinRel join = (JoinRel) call.rels[0];
List<RexNode> expList = new ArrayList<RexNode>(Arrays.asList(join.getChildExps()));
if (reduceExpressions(join, expList)) {
call.transformTo(
new JoinRel(
join.getCluster(),
join.getLeft(),
join.getRight(),
expList.get(0),
join.getJoinType(),
join.getVariablesStopped()));
// New plan is absolutely better than old plan.
call.getPlanner().setImportance(join, 0.0);
}
}