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planner: fix an unexpected result of the inlineprojection of TopN #58771

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merged 6 commits into from
Jan 8, 2025
Merged

planner: fix an unexpected result of the inlineprojection of TopN #58771

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8726e21
fix issue 58743
EricZequan Jan 7, 2025
ae682c0
update
EricZequan Jan 8, 2025
3f443c5
update
EricZequan Jan 8, 2025
861361e
add test
EricZequan Jan 8, 2025
5079385
update
EricZequan Jan 8, 2025
5d5d8cd
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EricZequan Jan 8, 2025
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12 changes: 11 additions & 1 deletion pkg/planner/core/operator/logicalop/logical_top_n.go
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,8 @@ func (lt *LogicalTopN) PruneColumns(parentUsedCols []*expression.Column, opt *op
child := lt.Children()[0]
var cols []*expression.Column

lt.InlineProjection(parentUsedCols, opt)
snapParentUsedCols := make([]*expression.Column, 0)
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snapParentUsedCols = append(snapParentUsedCols, parentUsedCols...)

lt.ByItems, cols = pruneByItems(lt, lt.ByItems, opt)
parentUsedCols = append(parentUsedCols, cols...)
Expand All @@ -92,6 +93,15 @@ func (lt *LogicalTopN) PruneColumns(parentUsedCols []*expression.Column, opt *op
if err != nil {
return nil, err
}
// If the length of parentUsedCols is 0, it means that the parent plan does not need this plan to output related
// results, such as: select count(*) from t
// So we set the schema of topN to 0. After inlineprojection, the schema of topN will be set to the shortest column
// in its child plan, and this column will not be used later.
if len(snapParentUsedCols) == 0 {
lt.SetSchema(nil)
}
lt.InlineProjection(snapParentUsedCols, opt)
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return lt, nil
}

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