julianhyde commented on a change in pull request #1589: [CALCITE-3508]
Strengthen outer Join to inner if it is under a Filter that discards null values
URL: https://github.com/apache/calcite/pull/1589#discussion_r347670650
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File path: core/src/main/java/org/apache/calcite/rel/rules/FilterJoinRule.java
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@@ -156,6 +161,52 @@ protected void perform(RelOptRuleCall call, Filter filter,
final List<RexNode> leftFilters = new ArrayList<>();
final List<RexNode> rightFilters = new ArrayList<>();
+ final int nFieldsLeft = join
+ .getInputs()
+ .get(0)
+ .getRowType()
+ .getFieldList()
+ .size();
+ final int nFieldsRight = join
+ .getInputs()
+ .get(1)
+ .getRowType()
+ .getFieldList()
+ .size();
+
+ final int nTotalFields = join.getRowType().getFieldList().size();
+ final int nSysFields = 0; // joinRel.getSystemFieldList().size();
+
+ // Setup two bit sets, one for the left side of the join indicating what
fields are present
+ // in the left side of the join and the other for the right side.
+ final ImmutableBitSet leftBitmap = ImmutableBitSet.range(
+ nSysFields, nSysFields + nFieldsLeft);
+ final ImmutableBitSet rightBitmap = ImmutableBitSet.range(
+ nSysFields + nFieldsLeft, nTotalFields);
+
+ // When a join can create nulls on the left (or right) leverage the filter
to determine if
+ // the join can cancel nulls on left (or right).
+ if (joinType.generatesNullsOnLeft() && filter != null) {
+ final RexVisitor<Boolean> mustMatchSideVisitor = new
TableNotNullable(leftBitmap);
+ final Boolean filterMustMatch =
filter.getCondition().accept(mustMatchSideVisitor);
+ if (filterMustMatch != null) {
+ if (filterMustMatch != Boolean.FALSE) {
+ joinType = joinType.cancelNullsOnLeft();
+ }
+ }
+ }
+
+ // When a join can create nulls on the right (or left) leverage the filter
to determine if
+ // the join can cancel nulls on right (or left).
+ if (joinType.generatesNullsOnRight() && filter != null) {
+ final RexVisitor<Boolean> mustMatchSideVisitor = new
TableNotNullable(rightBitmap);
+ final Boolean filterMustMatch =
filter.getCondition().accept(mustMatchSideVisitor);
+ if (filterMustMatch != null) {
+ if (filterMustMatch != Boolean.FALSE) {
Review comment:
I don't know what would be troublesome. I do know what we don't know what we
don't know. And therefore starting from scratch is a mistake.
A couple of examples:
* '(x IS NOT TRUE) IS NOT NULL' (the IS functions convert 3vl to 2vl, so,
like NOT they have complex truth tables)
* '(CASE WHEN x = 1 THEN 5 ELSE y END) > z' (you can isolate the expression
to left or right input only if you push '> z' into the CASE)
* and any expression that is deeply nested (e.g. contains NOT inside CASE
inside NOT)
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