fix(examples): apply relation aliases once - #24756
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RelationPlanning::Planned and RelationPlanning::Original began taking boxed values in apache@e8efd59, merged through apache#19672. The extending SQL guide retained the old constructors, so update the example to match the current API.
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Which issue does this PR close?
Rationale for this change
The official
TABLESAMPLErelation-planner example currently applies a relation alias twice. It recursively plans the underlying table while the alias is still attached, then returns that same alias with the completed sampled plan.RelationPlannerContext::plan(...)applies the first copy, and DataFusion appliesPlannedRelation::aliasa second time.This is subtle enough to miss in review, and the example is doing its job a little too well: VGI copied the same recursive-planning shape and returns the alias again.
The intended ownership rule is simple: remove the outer alias before recursively planning an inner relation, then return that alias with the finished extension plan so DataFusion applies it once, around the whole relation.
What changes are included in this PR?
TABLESAMPLEexample so the recursively planned base relation has no alias.PlannedRelationandRelationPlannerContext::planAPI docs and in the extending-SQL guide.RelationPlanningexample to use the current boxed variants.Are these changes tested?
Yes. The test checks the complete logical-plan shape and verifies that the relation alias and each column rename appear exactly once. As an ablation check, restoring the old
alias.clone()line makes the test fail with twoSubqueryAliasnodes and duplicate rename projections.I also ran the focused example test, example compilation,
cargo fmt --all, the required all-target/all-feature Clippy command with warnings denied, Rustdoc fordatafusion-expr, and the documentation Prettier check.Are there any user-facing changes?
The core planner's alias behavior is unchanged. The user-facing changes are a corrected official example and clearer documentation for extension authors.