[SPARK-43390][SQL] DSv2 allows CTAS/RTAS to reserve schema nullability #41070
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This was referenced May 5, 2023
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cloud-fan
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May 8, 2023
| * Return whether to reserve schema nullability of query output or forcibly use nullable schema | ||
| * on creating table implicitly, e.g. CTAS/RTAS. | ||
| */ | ||
| default boolean createTableReserveSchemaNullability() { |
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how about
/**
* If true, mark all the fields of the query schema as nullable when executing
* CREATE/REPLACE TABLE ... AS SELECT ... and creating the table.
*/
default boolean useNullableQuerySchema
beliefer
reviewed
May 8, 2023
| } | ||
| } | ||
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| class TestCreateTableReserveSchemaNullabilityCatalog extends InMemoryCatalog { |
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How about ForbidSchemaNullabilityCatalog ?
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"forbid" seems not accurate here, would prefer to use "reserve" to represent respecting the query schema nullability
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I means the name seems too long. Could you rename it with simple one ?
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Maybe "ReserveSchemaNullabilityCatalog"?
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changed to "ReserveSchemaNullabilityCatalog"
cloud-fan
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cloud-fan
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cloud-fan
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cloud-fan
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beliefer
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May 9, 2023
Contributor
|
thanks, merging to master! |
LuciferYang
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May 10, 2023
### What changes were proposed in this pull request? Add a new method `useNullableQuerySchema` in `Table`, to allow the DataSource implementation to declare whether they need to reserve schema nullability on CTAS/RTAS. ### Why are the changes needed? SPARK-28837 forcibly uses the nullable schema on CTAS/RTAS, which seems too aggressive: 1. The existing matured RDBMSs have different behaviors for reserving schema nullability on CTAS/RTAS, as mentioned in apache#25536, PostgreSQL forcibly uses the nullable schema, but MySQL respects the query's output schema nullability. 2. Some OLAP systems(e.g. ClickHouse) are perf-sensitive for nullable, and have strict restrictions on table schema, e.g. the primary keys are not allowed to be nullable. ### Does this PR introduce _any_ user-facing change? Yes, this PR adds a new DSv2 API, but the default implementation reserves backward compatibility. ### How was this patch tested? UTs are updated. Closes apache#41070 from pan3793/SPARK-43390. Authored-by: Cheng Pan <chengpan@apache.org> Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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What changes were proposed in this pull request?
Add a new method
useNullableQuerySchemainTableCatalog, to allow the DataSource implementation to declare whether they need to reserve schema nullability on CTAS/RTAS.Why are the changes needed?
SPARK-28837 forcibly uses the nullable schema on CTAS/RTAS, which seems too aggressive:
Does this PR introduce any user-facing change?
Yes, this PR adds a new DSv2 API, but the default implementation reserves backward compatibility.
How was this patch tested?
UTs are updated.