Bug#120641: Preserve FLOAT string formatting through ANY_VALUE

[DerZc]

What does this change do?

Condition pushdown replaces a materialized FLOAT field with its expression. Return the argument's FLOAT string representation from ANY_VALUE so this replacement preserves string-comparison results and NULL state.

Bug report: https://bugs.mysql.com/bug.php?id=120641

Why is it needed?

The affected execution path returns a different query result from the equivalent reference. The change preserves the expression or access-path semantics described above.

How was it tested?

On trunk at a1ef44f1d327b940a763b25eee2c6e146a0ebdb0:

• The unmodified server fails the new regression with a result mismatch.

• The patched server builds successfully.

• 16 query-result checks pass against separately established expected results, including repeated prepared statements.

• Native MTR passes: main.bug_120641, main.select_count, main.type_float, main.group_by.

• The regression passes with the prepared-statement protocol.

• The full database regression suite was not run.

• Added MTR coverage under mysql-test/.

• Ran scripts/ci/mtr.sh with its default selection; the explicit native and related tests above were run instead.

• Ran the full database regression suite.

Contributor checklist

• Changed C++ files are formatted with the repository .clang-format.
• One focused commit with a descriptive message.

AI assistance

• I did not use AI assistance for this contribution.
• I used AI assistance for this contribution.

OpenAI Codex assisted with implementation, regression test generation and review. The submitted change was checked with compilation, execution against independently established expected results, a failing unpatched regression, and the MTR tests listed above. No human review is claimed by these automated checks.

Areas touched

mysql-test, sql

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[RidhaOracle]

/codex

[github-actions]

✅ Codex PR Review completed successfully!

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[github-actions]

Found one correctness regression: the new FLOAT string delegation inherits ZEROFILL padding that materialization drops, making query results depend on condition pushdown. The inline comment includes a regression case and suggested correction.

Reviewed all four changed files and the relevant formatting, temporary-field, and pushdown paths. Static review only; no PR code or tests were executed.

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[github-actions]

[P2] Preserve the temporary FLOAT field's unpadded representation

Delegating to the argument's val_str() also inherits ZEROFILL padding. For a FLOAT(10,2) ZEROFILL column containing 1, this returns 0000001.00, whereas create_tmp_field_from_item() constructs the materialized ANY_VALUE result with zerofill=false, so it returns 1.00. Consequently, with derived_merge=off, the following predicate matches with derived_condition_pushdown=on and does not match with it off:

CREATE TABLE t (c FLOAT(10,2) ZEROFILL);
INSERT INTO t VALUES (1);
SELECT c
FROM (SELECT ANY_VALUE(c) AS c FROM t) AS d
WHERE c LIKE '000%';

Before this change, the inherited numeric conversion was unpadded in both paths. Please format the numeric result with FLOAT precision and the expression's decimals without inheriting source-field padding, and add coverage comparing pushdown on/off for this case.

[roylyseng]

Thank you for your contribution.
However, on further inspection, we concluded this is not a bug.
Combing FLOAT values and conversions to and from strings are inherently vulnerable and deviations may be expected due to internal handling precision issues.
In fact, it seems the result claimed to be correct in the bug report is actually incorrect.

[DerZc]

Hi @roylyseng I got it! Thanks for your work!