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fix: handle aliases in UNIONs better#18484

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systay merged 1 commit intovitessio:mainfrom
planetscale:fix-18469
Jul 24, 2025
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fix: handle aliases in UNIONs better#18484
systay merged 1 commit intovitessio:mainfrom
planetscale:fix-18469

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@systay systay commented Jul 24, 2025

Description

When planning UNIONs, Vitess was having a hard time handling column aliases correctly.

Related Issue(s)

Fixes #18469

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  • "Backport to:" labels have been added if this change should be back-ported to release branches
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fix: handle aliases in UNIONs better
8a3abeb 
Signed-off-by: Andres Taylor <andres@planetscale.com>
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vitess-bot bot commented Jul 24, 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 Jul 24, 2025
@github-actions github-actions bot added this to the v23.0.0 milestone Jul 24, 2025
@systay systay 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 Jul 24, 2025
dbussink
dbussink approved these changes Jul 24, 2025
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go/vt/vtgate/planbuilder/operators/union.go
offset := slices.IndexFunc(cols, func(expr *sqlparser.AliasedExpr) bool {
return e.Name.EqualString(expr.ColumnName())
offset := slices.IndexFunc(cols, func(column *sqlparser.AliasedExpr) bool {
if column.ColumnName() == expr.ColumnName() {
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I had to double check, but this looks to work also correctly if both sides don't have an alias set?

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@systay systay Jul 24, 2025

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exactly. we have tests of both variations.

@systay systay enabled auto-merge (squash) July 24, 2025 15:26
@systay systay merged commit f4c531d into vitessio:main Jul 24, 2025
104 of 116 checks passed
@systay systay deleted the fix-18469 branch July 24, 2025 15:34
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GrahamCampbell commented Jul 24, 2025

Should this be backported?

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systay commented Jul 25, 2025

Should this be backported?

I believe the rule is to only backport regressions or corruption bugs (corrupted data, but also corrupted results). Since this "just" fails to plan, we don't backport

morgo added a commit to morgo/vitess that referenced this pull request Jul 29, 2025
@morgo
Merge remote-tracking branch 'origin/master' into mtocker-virtual-sha…
1295e8b 
…rds-new2

* origin/master:
  Set up better dependency checks (vitessio#18508)
  bugfix: Plan group by only on top of derived tables correctly (vitessio#18505)
  Fix regression in v22 around new flag setup (vitessio#18507)
  Bump form-data from 4.0.1 to 4.0.4 in /web/vtadmin (vitessio#18473)
  Bump @babel/runtime from 7.26.0 to 7.27.6 in /web/vtadmin (vitessio#18467)
  Bump vite from 4.5.9 to 4.5.14 in /web/vtadmin (vitessio#18485)
  Fix for simple projection showing no fields (vitessio#18489)
  log.Info -> log.Infof in tabletserver for reloading ACLs (vitessio#18461)
  Fix scalar aggregation with literals in empty result sets (vitessio#18477)
  Avoid terminating atomic copy workflows on error if they are out of copy phase (vitessio#18475)
  Update runners to use cncf oracle vms (vitessio#18425)
  fix: handle aliases in UNIONs better (vitessio#18484)
  VReplication: Fix bug while reading _vt.vreplication record (vitessio#18478)
  Planner: Add comprehensive debug logging for query planner NoRewrite cases (vitessio#18476)
  Update email in Maintainers file (vitessio#18472)
  tablet manager's `ExecuteFetchAsDba` does not allow multiple queries (vitessio#18183)

Signed-off-by: Morgan Tocker <tocker@gmail.com>
@systay systay mentioned this pull request Aug 29, 2025
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@dbussink dbussink dbussink approved these changes

@frouioui frouioui frouioui approved these changes

@harshit-gangal harshit-gangal Awaiting requested review from harshit-gangal harshit-gangal is a code owner

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@arthurschreiber arthurschreiber Awaiting requested review from arthurschreiber arthurschreiber is a code owner

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Component: Query Serving Type: Bug

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Successfully merging this pull request may close these issues.

Bug Report: Scattered Union Broken With Column Alias + Limit

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