[SPARK-38332][SQL] Add the DATEADD() and DATE_ADD() aliases for TIMESTAMPADD()

[MaxGekk]

What changes were proposed in this pull request?

In the PR, I propose to add two aliases for the TIMESTAMPADD() function introduced by #35502:

• DATEADD()
• DATE_ADD()

Why are the changes needed?

1. To make the migration process from other systems to Spark SQL easier.
2. To achieve feature parity with other DBMSs.

Does this PR introduce any user-facing change?

No. The new aliases just extend Spark SQL API.

How was this patch tested?

1. By running the existing test suites:

$ build/sbt "test:testOnly *SQLKeywordSuite"

3. and new checks:

$ build/sbt "sql/testOnly org.apache.spark.sql.SQLQueryTestSuite -- -z date.sql"

[MaxGekk]

@srielau @entong @superdupershant Any feedback is welcome.

[HyukjinKwon]

I'm fine w/ this. Look fine.

[superdupershant]

Looks good except the return type shouldn't always be TIMESTAMP if the input expression and operation fit within a DATE type.
Sorry for missing this in the original TIMESTAMPADD change as well.

[superdupershant]

I think the convention is if the third argument is of type DATE the expression's return type is:

DATE if the unit is DAY or larger
TIMESTAMP if the unit is smaller than DAY i.e. (HOUR, MINUTE, SECOND, etc...)

[MaxGekk]

I don't think we should do such kind of changes in the PR which just introduces aliases. Let's do that separately w/ tests if the feature is supported by other DBMSs as well.

Also I would prefer to not link such changes to DATEADD since they affect TIMESTAMPADD. It is slightly strange to me that a timestamp function will return date type. Let's discuss this separately.

[cloud-fan]

Do you mean timestampadd can take date inputs but dateadd can't take timestamp inputs? Then it's not a simple alias any more.

[superdupershant]

@cloud-fan no both expressions can take date and timestamp inputs it is just a simple alias.

@MaxGekk yes I agree fixing it in a separate PR makes sense.

[superdupershant]

LGTM let's just fix the return types in a separate PR.

[superdupershant]

@cloud-fan no both expressions can take date and timestamp inputs it is just a simple alias.

@MaxGekk yes I agree fixing it in a separate PR makes sense.

[MaxGekk]

Merging to master. Thank you, @HyukjinKwon @superdupershant @cloud-fan @gengliangwang for review.