jinxing64 commented on a change in pull request #1451: [CALCITE-3334]
Refinement for Substitution-Based MV Matching
URL: https://github.com/apache/calcite/pull/1451#discussion_r324991111
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File path: core/src/main/java/org/apache/calcite/plan/SubstitutionVisitor.java
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@@ -916,18 +947,22 @@ public RexSimplify getSimplify() {
* Result of an application of a {@link UnifyRule} indicating that the
* rule successfully matched {@code query} against {@code target} and
* generated a {@code result} that is equivalent to {@code query} and
- * contains {@code target}.
+ * contains {@code target}. {@code triedEnough} indicates whether there's
Review comment:
As you can see -- In most cases, `triedEnough` is set to be `true`, the
behavior is consistent with the original logic, i.e. once a node of query
matches up with a result, it will not be matched again in following matching
iterations
(https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/SubstitutionVisitor.java#L515)
But in this PR, once a compensating `Calc` is generated, it will detect and
try to merge with its parent `Calc`
(https://github.com/apache/calcite/pull/1451/files#diff-442f8877d20c28297626599e9fa2a13dR1830).
In this case, the parent `Calc` should have the chance to be matched again
with nodes from `target` and `triedEnough` is set to be
`false`(https://github.com/apache/calcite/pull/1451/files#diff-442f8877d20c28297626599e9fa2a13dR1834)
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