[GitHub] [calcite] danny0405 commented on a change in pull request #1589: [CALCITE-3508] Strengthen Outer Joins based on FILTER clauses

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danny0405 commented on a change in pull request #1589: [CALCITE-3508] Strengthen Outer Joins based on FILTER clauses
URL: https://github.com/apache/calcite/pull/1589#discussion_r347078340
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/rules/FilterJoinRule.java
 ##########
 @@ -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:
   When the `filterMustMatch ` can be null ?

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