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[SPARK-30757][SQL][DOC] Update the doc on TableCatalog.alterTable's behavior

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### What changes were proposed in this pull request?

This PR updates the documentation on `TableCatalog.alterTable`s behavior on the order by which the requested changes are applied. It now explicitly mentions that the changes are applied in the order given.

### Why are the changes needed?

The current documentation on `TableCatalog.alterTable` doesn't mention which order the requested changes are applied. It will be useful to explicitly document this behavior so that the user can expect the behavior. For example, `REPLACE COLUMNS` needs to delete columns before adding new columns, and if the order is guaranteed by `alterTable`, it's much easier to work with the catalog API.

### Does this PR introduce any user-facing change?

Yes, document change.

### How was this patch tested?

Not added (doc changes).

Closes #27496 from imback82/catalog_table_alter_table.

Authored-by: Terry Kim <yuminkim@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
This commit is contained in:
Terry Kim 2020-02-10 19:04:49 +08:00 committed by Wenchen Fan
parent 58b9ca1e6f
commit 70e545a94d
1 changed files with 2 additions and 0 deletions
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sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/TableCatalog.java
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@ -134,6 +134,8 @@ public interface TableCatalog extends CatalogPlugin {
* Implementations may reject the requested changes. If any change is rejected, none of the
* changes should be applied to the table.
* <p>
* The requested changes must be applied in the order given.
* <p>
* If the catalog supports views and contains a view for the identifier and not a table, this
* must throw {@link NoSuchTableException}.
*