[SPARK-14518] [SQL] Support Comment in CREATE VIEW

[gatorsmile]

What changes were proposed in this pull request?

HQL Syntax: Create View

CREATE VIEW [IF NOT EXISTS] [db_name.]view_name [(column_name [COMMENT column_comment], ...) ]
[COMMENT view_comment]
[TBLPROPERTIES (property_name = property_value, ...)]
ASSELECT ...;

Add a support for the [COMMENT view_comment] clause

How was this patch tested?

Modified the existing test cases to verify the correctness.

[SparkQA]

Test build #55481 has finished for PR 12288 at commit 9c6ab48.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

cc @yhuai@andrewor14 Thanks!

[yhuai]

Should we just call it comment? Or, are we using description in other places?

[gatorsmile]

https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/interface.scala#L268

CatalogDatabase uses description as comment. Maybe comment is more straightforward. Let me change it. Thanks!

[yhuai]

@gatorsmile Thank you for working on it. How about we hold off the change until we merge https://github.com/apache/spark/pull/12271/files? That PR is adding the field for comment in the CatalogTable.

[gatorsmile]

Sure, no problem. : )

[SparkQA]

Test build #55485 has finished for PR 12288 at commit 6f0f4cb.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #55785 has finished for PR 12288 at commit bfa4ea5.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

@yhuai@andrewor14@cloud-fan@liancheng

After the merge of Create Table, this PR is changed by using the latest CatalogTable. It is ready for review. Thanks!

[cloud-fan]

I'd like to do assert(tableMetadata.properties.get("comment") == "BLABLA")

[gatorsmile]

Sure, do it now. Thanks!

[cloud-fan]

LGTM except one minor comment

[SparkQA]

Test build #55816 has finished for PR 12288 at commit df4f5c2.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[yhuai]

Thanks. Merging to master.