pushdown projection handle empty projections #7257
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smiklos
commented
Aug 10, 2023
| .insert(scan.projected_schema.fields()[0].qualified_column()); | ||
| push_down_scan(&used_columns, scan, true)? | ||
| let new_scan = push_down_scan(&used_columns, scan, true)?; | ||
| plan.with_new_inputs(&[new_scan])? |
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This call feels like it was just left out accidentally
smiklos
commented
Aug 10, 2023
| let new_filter = child_plan.with_new_inputs(&[new_projection])?; | ||
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| generate_plan!(projection_is_empty, plan, new_filter) | ||
| plan.with_new_inputs(&[new_filter])? |
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in this branch projection_is_empty is false so new_filter was returned as is. However that means it becomes a filter plan with a different schema. so this way we keep the original plan and change its inputs
smiklos
commented
Aug 10, 2023
| assert_schema_is_the_same(rule.name(), &new_plan, &plan)?; | ||
| new_plan = plan; | ||
| Ok(Some(optimized_plan)) => { | ||
| assert_schema_is_the_same( |
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I think this assertion should be chained with result first such that the error handling below can kick in and rules that change the schema can also be skipped if needed.
smiklos
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Which issue does this PR close?
Closes #7241.
Rationale for this change
It is possible to select no columns at all when using
exclude. In such cases thepush_down_projectionrule will alter the schema which will then blow up in the optimizer as rules are not suppose to change the plan's schema.I can't tell if empty selection is even legit..
What changes are included in this PR?
Both empty projection and empty projection with filter has been tweaked to do not alter the original schema.
Are these changes tested?
Yeah
Are there any user-facing changes?
No
No
No