jduo commented on code in PR #3616:
URL: https://github.com/apache/calcite/pull/3616#discussion_r1529081391
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core/src/main/java/org/apache/calcite/plan/SubstitutionVisitor.java:
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@@ -649,6 +661,96 @@ assert rowTypesAreEquivalent(
return substitutions;
}
+ /**
+ * Find out the replacements belongs to the real substitution and undo the
rest.
+ * The rest replacements are exploratory, they are no more needed when this
attempt finished.
+ */
+ private List<Replacement> undoAndRemoveExploratoryReplacements(
+ List<Replacement> attempted, List<MutableRel> targetDescendants,
+ MutableRel replacement, boolean lastIsFinalReplacement) {
+ final List<Replacement> realReplacements = new ArrayList<>();
+ final List<Replacement> exploratoryReplacements =
+ new ArrayList<>(lastIsFinalReplacement
+ ? attempted.subList(0, attempted.size() - 1)
+ : attempted);
+ findOutRealReplacements(
+ exploratoryReplacements,
+ realReplacements,
+ null,
+ targetDescendants,
+ replacement);
+ Collections.reverse(realReplacements);
+ exploratoryReplacements.removeAll(realReplacements);
+ undoReplacement(exploratoryReplacements);
+ if (lastIsFinalReplacement) {
+ realReplacements.add(attempted.get(attempted.size() - 1));
+ }
+ return realReplacements;
+ }
+
+ private void findOutRealReplacements(
+ List<Replacement> src, List<Replacement> result, @Nullable Replacement
last,
+ List<MutableRel> targetDescendants, MutableRel replacement) {
+ if (src == null || src.isEmpty()) {
+ return;
+ }
+ final Replacement current = src.get(src.size() - 1);
+ if (last == null || isPrevReplacement(current, last)) {
+ result.add(current);
+ last = current;
+ }
+ if (isFirstReplacement(current, targetDescendants, replacement)) {
+ return;
+ }
+ findOutRealReplacements(
+ src.subList(0, src.size() - 1),
+ result,
+ last,
+ targetDescendants,
+ replacement);
+ }
+
+ /**
+ * Return true when x replacement is the previous one of y.
+ */
+ private boolean isPrevReplacement(Replacement x, Replacement y) {
+ final MutableRel prev = x.after;
+ final MutableRel next = y.before;
+ if (prev == next) {
+ return true;
+ }
+ final MutableRel prevParent = prev.getParent();
+ assert prevParent != null;
+ for (MutableRel cur : MutableRels.descendants(next)) {
+ if (cur == prevParent) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Return true when x is the first one of real replacements chain,
+ * which the before of it is not the part of the targetDescendants and is
not replacement.
+ */
+ private boolean isFirstReplacement(
+ Replacement r,
+ List<MutableRel> targetDescendants,
+ MutableRel replacement) {
+ final MutableRel before = r.before;
+ for (MutableRel cur : MutableRels.descendants(before)) {
+ if (replacement.equals(cur)) {
+ return false;
+ }
+ for (MutableRel targetDescendant : targetDescendants) {
Review Comment:
Does this need to descend again to MutableRels.descendants(targetDescendant)?
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