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@ghostframe ghostframe commented Oct 3, 2025

Description

Addresses #9408

Setting SQL SELECT LIMIT through session variables or JDBC's .setMaxRows method, both apply to subqueries which yields erroneous results.
This query on its own, returns 3:

SELECT count(*) from
(select 1 AS num UNION ALL
SELECT 2 UNION ALL
SELECT 3) as subselect

If you do SET SESSION sql_select_limit = 1, run it again, then it returns 1, which is wrong - this is applying a LIMIT to the subquery instead.
With the fixed branch ,it doesn't.
This is a long shot at fixing it, first PR here so please let me know of any edge cases

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vitess-bot bot commented Oct 3, 2025

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@vitess-bot vitess-bot bot added NeedsBackportReason If backport labels have been applied to a PR, a justification is required NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Oct 3, 2025
@github-actions github-actions bot added this to the v23.0.0 milestone Oct 3, 2025
@ghostframe ghostframe force-pushed the fix-limit-propagates-to-subqueries branch from fcbeb1e to 9048039 Compare October 4, 2025 12:14
@systay systay modified the milestones: v23.0.0, v24.0.0 Oct 8, 2025
@timvaillancourt timvaillancourt added Component: VTTablet Component: VTGate Backport to: release-21.0 Needs to be backport to release-21.0 Backport to: release-22.0 Needs to be backport to release-22.0 Backport to: release-23.0 Needs to be backport to release-23.0 Type: Bug Type: Compatibility Bug and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Oct 16, 2025
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codecov bot commented Oct 16, 2025

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.50%. Comparing base (f8dafc7) to head (9048039).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files
@@            Coverage Diff             @@
##             main   #18716      +/-   ##
==========================================
+ Coverage   67.49%   67.50%   +0.01%     
==========================================
  Files        1606     1606              
  Lines      263729   263729              
==========================================
+ Hits       178009   178040      +31     
+ Misses      85720    85689      -31     

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@systay systay mentioned this pull request Oct 16, 2025
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@timvaillancourt timvaillancourt removed the Backport to: release-21.0 Needs to be backport to release-21.0 label Oct 17, 2025
@timvaillancourt timvaillancourt self-requested a review October 17, 2025 14:36
@systay systay mentioned this pull request Oct 27, 2025
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3 participants