ESQL: push down LIMIT past LOOKUP JOIN #118495
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...main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/PushDownAndCombineLimits.java
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| public void testPushdownLimitsPastLeftJoin() { | ||
| var leftChild = emptySource(); | ||
| var rightChild = new LocalRelation(Source.EMPTY, List.of(fieldAttribute()), LocalSupplier.EMPTY); | ||
| assertNotEquals(leftChild, rightChild); |
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Gotta be very careful here, you never know.
| @@ -63,8 +62,10 @@ public LogicalPlan rule(Limit limit) { | |||
| } | |||
| } | |||
| } else if (limit.child() instanceof Join join) { | |||
| if (join.config().type() == JoinTypes.LEFT && join.right() instanceof LocalRelation) { | |||
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Wondering why the previous restriction to LocalRelation (even if that's what was expected before). Anyways, should be good this way now.
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That came from when we only had LOOKUP (aka 🐔 ) and INLINESTATS to consider. Both of these ended up with a LocalRelation on the right, and we didn't want to implement this in all generality because the semantics were not 100% clear.
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Fix elastic#117698 by enabling push down of `LIMIT` past `LEFT JOIN`s. There is a subtle point here: our `LOOKUP JOIN` currently _exactly preserves the number of rows from the left hand side_. This is different from SQL, where `LEFT JOIN` will return _at least one row for each row from the left_, but may return multiple rows in case of multiple matches. We, instead, throw multiple matches into multi-values, instead. (C.f. [tests that I'm about to add](https://github.com/elastic/elasticsearch/pull/118471/files#diff-334f3328c5f066a093ed8a5ea4a62cd6bcdb304b660b15763bb4f64d0e87ed7cR365-R369) that demonstrate this.) If we were to change our semantics to match SQL's, we'd have to adjust the pushdown, too.
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Fix #117698 by enabling push down of `LIMIT` past `LEFT JOIN`s. There is a subtle point here: our `LOOKUP JOIN` currently _exactly preserves the number of rows from the left hand side_. This is different from SQL, where `LEFT JOIN` will return _at least one row for each row from the left_, but may return multiple rows in case of multiple matches. We, instead, throw multiple matches into multi-values, instead. (C.f. [tests that I'm about to add](https://github.com/elastic/elasticsearch/pull/118471/files#diff-334f3328c5f066a093ed8a5ea4a62cd6bcdb304b660b15763bb4f64d0e87ed7cR365-R369) that demonstrate this.) If we were to change our semantics to match SQL's, we'd have to adjust the pushdown, too.
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Fix elastic#117698 by enabling push down of `LIMIT` past `LEFT JOIN`s. There is a subtle point here: our `LOOKUP JOIN` currently _exactly preserves the number of rows from the left hand side_. This is different from SQL, where `LEFT JOIN` will return _at least one row for each row from the left_, but may return multiple rows in case of multiple matches. We, instead, throw multiple matches into multi-values, instead. (C.f. [tests that I'm about to add](https://github.com/elastic/elasticsearch/pull/118471/files#diff-334f3328c5f066a093ed8a5ea4a62cd6bcdb304b660b15763bb4f64d0e87ed7cR365-R369) that demonstrate this.) If we were to change our semantics to match SQL's, we'd have to adjust the pushdown, too.
maxhniebergall
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Fix elastic#117698 by enabling push down of `LIMIT` past `LEFT JOIN`s. There is a subtle point here: our `LOOKUP JOIN` currently _exactly preserves the number of rows from the left hand side_. This is different from SQL, where `LEFT JOIN` will return _at least one row for each row from the left_, but may return multiple rows in case of multiple matches. We, instead, throw multiple matches into multi-values, instead. (C.f. [tests that I'm about to add](https://github.com/elastic/elasticsearch/pull/118471/files#diff-334f3328c5f066a093ed8a5ea4a62cd6bcdb304b660b15763bb4f64d0e87ed7cR365-R369) that demonstrate this.) If we were to change our semantics to match SQL's, we'd have to adjust the pushdown, too.
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Fix #117698 by enabling push down of
LIMITpastLEFT JOINs.There is a subtle point here: our
LOOKUP JOINcurrently exactly preserves the number of rows from the left hand side. This is different from SQL, whereLEFT JOINwill return at least one row for each row from the left, but may return multiple rows in case of multiple matches. We, instead, throw multiple matches into multi-values, instead. (C.f. tests that I'm about to add that demonstrate this.)If we were to change our semantics to match SQL's, we'd have to adjust the pushdown, too.