tree 97b5483a6327a3a916d277b6d1452ebcbd0e6876
parent 1bf92120dd4cf7df3fd9764ef9fcb2b061b87644
author xuzhou <peter.cose.seu@gmail.com> 1576142366 +0800
committer Impala Public Jenkins <impala-public-jenkins@cloudera.com> 1578586678 +0000

IMPALA-9035: Simplify casting string to timestamp.

This change will help with queries generated by some BI tools.
Case 1:
Simplify 'string -> bigint -> timestamp' TO 'string -> timestamp':
cast(unix_timestamp('timestr') as timestamp) ->
cast('timestr' as timestamp)
Case 2:
Simplify 'string[fmt] -> bigint -> timestamp' TO 'string -> timestamp':
cast(unix_timestamp('timestr', 'fmt') as timestamp) ->
to_timestamp('timestr', 'fmt')

Tests:
Add front-end tests in ExprRewriteRulesTest.

Change-Id: I4ed72d6e7886eaf50d2be60cf45170ffaef5e72d
Reviewed-on: http://gerrit.cloudera.org:8080/14896
Reviewed-by: Attila Jeges <attilaj@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>