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Bug#121574: Wrong result for subquery on constant column of merged derived table - #865

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Bug#121574: Wrong result for subquery on constant column of merged derived table#865
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ToKliar:bug121574

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@ToKliar

@ToKliar ToKliar commented Oct 22, 2026

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What does this change do?

Fixes BUG#121574 (https://bugs.mysql.com/bug.php?id=121574): a subquery that
refers to a constant column of a merged derived table on the inner side of an
outer join returns wrong results for NULL-complemented rows.

Why is it needed?

The constant column depends on the derived table's first inner table, but
used_tables_for_level() only reports Item_field columns, so the containing
subquery did not depend on that table. The fix adds it to the subquery's used
tables when resolving the outer reference and after semi-join pullout.

How was it tested?

  • Added/updated MTR tests under mysql-test/
  • scripts/ci/mtr.sh passes locally
  • Ran the relevant full suite (name it): main.derived, also with --hypergraph

Contributor checklist

  • Code is formatted (scripts/ci/format.sh)
  • Commits are focused with descriptive messages

AI assistance

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

Areas touched

optimizer

@ToKliar
Bug#121574: Wrong result for subquery on constant column of merged de…
27ae2a7 
…rived table

A constant column of a merged derived table on the inner side of an
outer join depends on its first inner table, but the subquery that
refers to it did not, because used_tables_for_level() only reports
Item_field columns. The subquery then returned wrong results for
NULL-complemented rows.

Also add the first inner table of such view references to the
subquery's used tables, both when resolving the outer reference and
after semi-join pullout.
@ToKliar
ToKliar requested a review from a team October 22, 2026 07:26
@oracle-contributor-agreement

oracle-contributor-agreement Bot commented Oct 22, 2026

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Thank you for your pull request and welcome to our community! To contribute, please sign the Oracle Contributor Agreement (OCA).
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@oracle-contributor-agreement oracle-contributor-agreement Bot added the OCA Required At least one contributor does not have an approved Oracle Contributor Agreement. label Oct 22, 2026
@github-actions github-actions Bot added the Tests Changes touching test code or test data label Oct 22, 2026
@ogrovlen ogrovlen added the Optimizer Changes touching optimizer code label Oct 22, 2026
@github-actions github-actions Bot added the Build Failed PR build failed label Oct 22, 2026
@ToKliar

ToKliar commented Oct 22, 2026

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The Debug build and MTR failures are unrelated to this change: CMake fails at
configure time because libudev-dev is missing on the runner
("-DWITH_AUTHENTICATION_WEBAUTHN=ON, but missing required libraries").
scripts/ci/bootstrap.sh does not install libudev-dev, and the same failure
appears on other recent PRs (e.g. #862, #864), possibly since ubuntu-latest
moved to Ubuntu 26. The change builds locally and main.derived passes,
including with --hypergraph.

@RidhaOracle

RidhaOracle commented Oct 22, 2026

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Yes you are right @ToKliar I am looking into it

@ToKliar

ToKliar commented Oct 23, 2026

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Note: Bug#121574 was closed as a duplicate of Bug#121454, but they are
separate problems. This PR fixes Bug#121574 only; the test case in
Bug#121454 still fails with this patch. Details:
https://bugs.mysql.com/bug.php?id=121454

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@seemasundara seemasundara Awaiting requested review from seemasundara seemasundara is a code owner
@gopshank gopshank Awaiting requested review from gopshank gopshank is a code owner

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@ToKliar @RidhaOracle @ogrovlen