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fix: ensure mutual compatibility of the two input schemas from recursive CTEs - #9795
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jonahgao
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Mar 25, 2024
| static_fields_len, recurive_fields_len | ||
| ); | ||
| } | ||
| // Ensure that the recursive term has the same field types as the static term |
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Not sure if it's necessary to ensure that the field names are the same.I tested some queries, and none of them failed.
The union operator uses project_with_column_index only ensures the field names of projection plans are the same.
DataFusion CLI v36.0.0
❯ -- The field names of the two input are the same.
explain select 1 union all select 2;
+--------------+------------------------------------+
| plan_type | plan |
+--------------+------------------------------------+
| logical_plan | Union |
| | Projection: Int64(1) AS Int64(1) |
| | EmptyRelation |
| | Projection: Int64(2) AS Int64(1) |
| | EmptyRelation |
+--------------+------------------------------------+
❯ -- The field names of the two input are different.
explain select 1 union all values(2);
+--------------+------------------------------------+
| plan_type | plan |
+--------------+------------------------------------+
| logical_plan | Union |
| | Projection: Int64(1) AS Int64(1) |
| | EmptyRelation |
| | Values: (Int64(2)) |
+--------------+------------------------------------+
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Given the tests all pass this seems like a good plan to me.
alamb
approved these changes
Mar 27, 2024
| static_fields_len, recurive_fields_len | ||
| ); | ||
| } | ||
| // Ensure that the recursive term has the same field types as the static term |
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Given the tests all pass this seems like a good plan to me.
Lordworms
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Apr 1, 2024
…ive CTEs (apache#9795) * fix: Ensure mutual compatibility of the two input schemas from recursive CTEs * fix typo
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Which issue does this PR close?
Closes #9794.
Rationale for this change
Make the schema of the recursive term compatible with the static term.
This differs from the handling of the ordinary union operator. We can't change the static term's schema, otherwise we would have to recreate the logic plan of the recursive term, as it depends on the static term through the work table.
That is to say, we use the schema of the static term as the final schema for CTE.
DuckDB also adopted a similar approach.
D WITH RECURSIVE my_cte AS( SELECT 1::int AS a UNION ALL SELECT a::bigint+2 FROM my_cte WHERE a<3 ) SELECT a,typeof(a) FROM my_cte; ┌───────┬───────────┐ │ a │ typeof(a) │ │ int32 │ varchar │ ├───────┼───────────┤ │ 1 │ INTEGER │ │ 3 │ INTEGER │ └───────┴───────────┘The output type is
INTEGERfrom the static term, notBIGINT.What changes are included in this PR?
Check and coerce the schemas of recursive CTE's inputs.
Are these changes tested?
Yes
Are there any user-facing changes?
No