release-25.3: opt: fix placeholder scan NULL semantics #159069
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Fixes cockroachdb#158945 Release note (bug fix): A bug has been fixed which could cause incorrect results. The bug has existed since v21.2. From v21.2 up to v25.3, the bug only presented when all of the following were true: - The query was run with an explicit or implicit prepared statement. - The query had an equality filter on a placeholder and a UNIQUE column. - The column contained NULL values. - The placeholder was assigned to NULL during execution. In this case, the query could return rows in which the column's value is NULL, which violates SQL NULL-equality semantics. The correct result set should always be empty. Starting in v25.4, the requirements were loosened slightly. It was no longer necessary for the column to be UNIQUE. The bug could reproduce if the column was included in any index.
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Thanks for opening a backport. Before merging, please confirm that the change does not break backwards compatibility and otherwise complies with the backport policy. Include a brief release justification in the PR description explaining why the backport is appropriate. All backports must be reviewed by the TL for the owning area. While the stricter LTS policy does not yet apply, please exercise judgment and consider gating non-critical changes behind a disabled-by-default feature flag when appropriate. |
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Backport 1/3 commits from #159001.
/cc @cockroachdb/release
opt: fix placeholder scan NULL semantics
Fixes #158945
Release note (bug fix): A bug has been fixed which could cause incorrect
results. The bug has existed since v21.2. From v21.2 up to v25.3, the
bug only presented when all of the following were true:
column.
In this case, the query could return rows in which the column's value is
NULL, which violates SQL NULL-equality semantics. The correct result set
should always be empty.
Starting in v25.4, the requirements were loosened slightly. It was no
longer necessary for the column to be UNIQUE. The bug could reproduce if
the column was included in any index.
Release justification: Low-risk bug fix.