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Cherry pick #108423 to 26.5: Throw ILLEGAL_COLUMN when _distance is selected directly in vector search queries#108747
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robot-ch-test-poll4 merged 4 commits intoJun 28, 2026
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…arch queries
The `_distance` virtual column is internal to the vector search optimization and
populated only when the optimized plan rewrites the query. Previously, referencing
it directly in SELECT with an ORDER BY distance function caused a LOGICAL_ERROR
("Vector column unexpectedly already replaced") because the optimizer tried to add
`_distance` to the read list while it was already there from the user's SELECT.
Now this case throws a user-facing ILLEGAL_COLUMN error with a clear message
directing users to use the distance function (L2Distance, cosineDistance) in
ORDER BY instead.
The check is placed in both the first pass (tryUseVectorSearch) and the second pass
(optimizeVectorSearchSecondPass) for defense-in-depth coverage.
Closes: ClickHouse/clickhouse-core-incidents#1654
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Throw `ILLEGAL_COLUMN` when `_distance` is selected directly in vector search queries
robot-ch-test-poll4
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Original pull-request #108423
Do not merge this PR manually
This pull-request is a first step of an automated backporting.
It contains changes similar to calling
git cherry-picklocally.If you intend to continue backporting the changes, then resolve all conflicts if any.
Otherwise, if you do not want to backport them, then just close this pull-request.
The check results does not matter at this step - you can safely ignore them.
Troubleshooting
If the conflicts were resolved in a wrong way
If this cherry-pick PR is completely screwed by a wrong conflicts resolution, and you want to recreate it:
pr-cherrypicklabel from the PRYou also need to check the Original pull-request for
pr-backports-createdlabel, and delete if it's presented thereThe PR source
The PR is created in the CI job