xuzifu666 commented on code in PR #5132:
URL: https://github.com/apache/calcite/pull/5132#discussion_r3680782352
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core/src/main/java/org/apache/calcite/rel/rules/PruneEmptyRules.java:
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@@ -542,6 +560,30 @@ public interface SortFetchZeroRuleConfig extends
PruneEmptyRule.Config {
}
}
+ /** Configuration for a rule that prunes a Sort if its {@code OFFSET} skips
at
+ * least as many rows as its input can ever produce. */
+ @Value.Immutable
+ public interface SortOffsetGreaterThanMaxRowsRuleConfig extends
PruneEmptyRule.Config {
+ SortOffsetGreaterThanMaxRowsRuleConfig DEFAULT =
+ ImmutableSortOffsetGreaterThanMaxRowsRuleConfig.of()
+ .withOperandSupplier(b -> b.operand(Sort.class).anyInputs())
+ .withDescription("PruneSortOffsetGreaterThanMaxRows");
+
+ @Override default PruneEmptyRule toRule() {
+ return new RemoveEmptySingleRule(this) {
+ @Override public boolean matches(final RelOptRuleCall call) {
+ final Sort sort = call.rel(0);
+ // Only consider a static (non-dynamic) OFFSET. If the offset skips
at
+ // least as many rows as the input can ever produce, the Sort returns
+ // no rows. RelMdMaxRowCount#getMaxRowCount(Sort) already subtracts
the
+ // offset from the input row count, so the Sort is definitely empty.
+ return sort.offset instanceof RexLiteral
+ && RelMdUtil.isRelDefinitelyEmpty(call.getMetadataQuery(), sort);
Review Comment:
Yes, I merged SORT_FETCH_ZERO_INSTANCE and SORT_OFFSET_INSTANCE into a
single SORT_EMPTY_INSTANCE rule that simply checks
RelMdUtil.isRelDefinitelyEmpty. This covers LIMIT 0, OFFSET >= maxRowCount, and
empty input with one rule and no extra complexity. SORT_FETCH_ZERO_INSTANCE is
kept as a deprecated alias for backward compatibility. This impact should be
minimal.
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