fix: make replace empty search string a no-op#22357
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There's also #22275 for this issue, although I think this version is slightly better. |
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@garyconan1224
Thanks for working on this.
Looks 👍 to me
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We should also update (or remove) the comment describing the behavior for "empty-from" in benches/replace.rs. You could argue we can now remove those benchmark cases anyway, since the empty-from behavior is now straightforward and unlikely to be a perf hotspot.
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@garyconan1224 could you fix the remaining CI failures? |
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fyi another PR was raised for this would be good to see if we can get this PR over the line, otherwise we can defer to the other PR instead |
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use builder.append_value(string) for the no-op instead of the append_with closure, per the suggestion from apache#22357. also drop the replace_string_empty_from benches since they were timing the old char-interleaving path this PR removes.
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## Which issue does this PR close? - Closes apache#22253 - Closes apache#22357 ## Rationale for this change PostgreSQL returns the input unchanged when `replace` is called with an empty `from`. DataFusion was instead inserting `to` before every character and at both ends, so `replace('abc', '', 'x')` returned `xaxbxcx`. This PR brings the behaviour in line with PostgreSQL. Part of the PG-compatibility cleanup tracked in apache#22247. ## What changes are included in this PR? - `datafusion/functions/src/string/replace.rs`: the empty-`from` branch in `apply_replace` now writes the input verbatim instead of inserting `to`. Added a `LargeUtf8` unit test for the new behaviour. - `datafusion/sqllogictest/test_files/string/string_literal.slt`: four new SLT asserts covering the `Utf8`, `Dictionary`, `Utf8View`, and `LargeUtf8` paths. - `datafusion/sqllogictest/test_files/string/string_query.slt.part`: updated four expected rows that were asserting the old buggy output. ## Are these changes tested? Yes. The unit test in `replace.rs` covers the `LargeUtf8` path, and the four new SLT asserts in `string_literal.slt` cover the remaining Arrow string encodings end-to-end. The full SLT suite passes locally. ## Are there any user-facing changes? Yes. `replace(str, '', x)` now returns `str` unchanged instead of inserting `x` between every character. This matches PostgreSQL. --------- Signed-off-by: Amogh Ramesh <ramogh2404@gmail.com>
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Which issue does this PR close?
Closes #22253.
Rationale for this change
PostgreSQL treats
replacewith an empty search string as a no-op. DataFusion currently inserts the replacement string around each character, soreplace('abc', '', 'x')returnsxaxbxcxinstead ofabc.What changes are included in this PR?
fromargument toreplaceis empty.Are these changes tested?
git diff --checkcargo/rustcinstalled; the added SQLLogicTest cases are intended for CI verification.