[opt](nereids) rewrite element_at(split_by_string(s,sep),n) to split_part - #66181
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[opt](nereids) rewrite element_at(split_by_string(s,sep),n) to split_part#66181Baymine wants to merge 1 commit into
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### What problem does this PR solve? Issue Number: close apache#66179 Problem Summary: `element_at(split_by_string(s, d), n)` builds the whole split array (a PODArray allocation and a memcpy per part, per row) and then picks a single entry. This rewrites it to `split_part(s, d, n)`, which short-circuits as soon as it locates the n-th delimiter, eliminating the intermediate array and the trailing-parts work. The rewrite is semantics-preserving. The two forms differ only when the string yields no n-th part: `element_at` returns NULL while `split_part` can return ''. To neutralize this, the rule only rewrites the ROOT of a top-level filter conjunct (where NULL and false both drop the row) and is guarded to: - EqualTo / InPredicate with a NON-EMPTY string-literal RHS (or an IN-list of non-empty string literals), so a comparison against '' yields false, not true; - a NON-EMPTY string-literal separator (an empty/column separator diverges); - a NON-NEGATIVE int-literal index (negative back-counting uses rfind and can land on a different boundary for self-overlapping multi-char separators). It deliberately does NOT recurse into NOT / OR / CASE, where NULL and '' are no longer interchangeable. ### Release note None ### Check List (For Author) - Test <!-- At least one of them must be included. --> - [ ] Regression test - [x] Unit Test - [ ] Manual test (add detailed scripts or steps below) - [ ] No need to test or manual test. Explain why: - Behavior changed: - [x] No. - [ ] Yes. - Does this need documentation? - [x] No. - [ ] Yes.
Baymine
requested review from
924060929,
englefly,
morrySnow and
starocean999
as code owners
July 28, 2026 12:12
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Thank you for your contribution to Apache Doris. Please clearly describe your PR:
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TPC-H: Total hot run time: 29631 ms |
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TPC-DS: Total hot run time: 177840 ms |
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ClickBench: Total hot run time: 24.91 s |
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What problem does this PR solve?
Issue Number: close #66179
Related PR: N/A
Problem Summary:
element_at(split_by_string(s, d), n)builds the whole split array (a PODArray allocation and a memcpy per part, per row) and then picks a single entry. This rewrites it tosplit_part(s, d, n), which short-circuits as soon as it locates the n-th delimiter, eliminating the intermediate array and the trailing-parts work.The rewrite is semantics-preserving. The two forms differ only when the string yields no n-th part:
element_atreturns NULL whilesplit_partcan return''. To neutralize this, the rule only rewrites the ROOT of a top-level filter conjunct (where NULL and false both drop the row) and is guarded to:''yields false, not true;It deliberately does NOT recurse into NOT / OR / CASE, where NULL and
''are no longer interchangeable.Release note
None
Check List (For Author)
Test
Behavior changed:
Does this need documentation?
Check List (For Reviewer who merge this PR)