xuzifu666 commented on code in PR #5392:
URL: https://github.com/apache/calcite/pull/5392#discussion_r4492397794
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core/src/main/java/org/apache/calcite/sql2rel/RelDecorrelator.java:
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@@ -1757,21 +1757,26 @@ private Frame createFrameWithValueGenerator(RelNode
rel, Frame frame,
* ensuring that we only map the correlation variable to a local field or
* expression from the current relational expression (e.g., a {@link
RexInputRef}),
* rather than to another correlation variable.
+ *
+ * <p>{@code IS NOT DISTINCT FROM} establishes the same equivalence as
+ * {@code =} (it compares values null-safely), so it is also recognized.
*/
private static void findCorrelationEquivalent(CorRef correlation, RexNode e)
throws Util.FoundOne {
switch (e.getKind()) {
case EQUALS:
+ case IS_NOT_DISTINCT_FROM:
final RexCall call = (RexCall) e;
final List<RexNode> operands = call.getOperands();
- if (!RexUtil.containsFieldAccess(operands.get(1))
- && references(operands.get(0), correlation)) {
- throw new Util.FoundOne(operands.get(1));
- }
- if (!RexUtil.containsFieldAccess(operands.get(0))
- && references(operands.get(1), correlation)) {
- throw new Util.FoundOne(operands.get(0));
- }
+ // For IS NOT DISTINCT FROM, binding is only sound when the local
+ // operand is NOT NULL: the residual filter
+ // {@code IS NOT DISTINCT FROM(x, x)} is then always true, and the join
Review Comment:
Agreed, "residual filter" was undefined. What I meant: after decorrelation,
the original Filter stays on the inner side of the join with $cor0 substituted
by its binding, leaving condition IS NOT DISTINCT FROM(x, x) (see the
LogicalFilter in the test's planAfter). That residual condition is always true,
so it's harmless; the null-safe semantics are carried by the join condition
instead which is exactly why the local operand must be NOT NULL, otherwise =
would drop rows the original condition accepted. I've reworded the comment to
spell this out.
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