opt: explore splitting disjunction over same column #157083
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The SplitDisjunction rules did not consider disjunctions over expressions referencing the same column interesting, because normally these disjunctions can become multiple spans in the same constrained scan. There is one special case, however, where disjunctions over the same column might be interesting: if the table has multiple partial indexes with different predicates referencing that column. In that case we might be able to use a different partial index for each side of the disjunction. Fixes: cockroachdb#157073 Release note (performance improvement): This commit teaches the optimizer to split disjunctions on the same column into unions when there are multiple partial indexes with different predicates referencing that column.
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mgartner
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Nov 8, 2025
| // If the current expression ColSet matches leftColSet (and we're not using | ||
| // the exception for multiple referencing partial index predicates) add the | ||
| // expr to the left group. Otherwise, add it to the right group. | ||
| if leftColSet.Equals(cols) && !c.multiplePartialIndexesReferencing(sp, leftColSet) { |
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I think we could be stricter and keep a set of the partial indexes with predicates implied by the left exprs, and when examining an expr we can add it to right exprs if its colset is equal to leftColSet and it implies at least one partial index predicate not implied by the left expressions.
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| opt expect=SplitDisjunction | ||
| SELECT c, a FROM t157073 WHERE c = 5 AND (b < 0 OR b >= 9990) |
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Tests with multiple adjacent disjunctions would be interesting to see.
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The SplitDisjunction rules did not consider disjunctions over expressions referencing the same column interesting, because normally these disjunctions can become multiple spans in the same constrained scan. There is one special case, however, where disjunctions over the same column might be interesting: if the table has multiple partial indexes with different predicates referencing that column. In that case we might be able to use a different partial index for each side of the disjunction.
Fixes: #157073
Release note (performance improvement): This commit teaches the optimizer to split disjunctions on the same column into unions when there are multiple partial indexes with different predicates referencing that column.