englefly opened a new pull request, #16854:
URL: https://github.com/apache/doris/pull/16854
(cherry pick from master)
For performance reason, we want to remove constant column from
groupingExprs. For example:
`select sum(T.A) from T group by T.B, 'xyz'` is equivalent
to `select sum(T.A) from T group by T.B`
We can remove constant column `abc` from groupingExprs.
But there is an exception when all groupingExpr are constant For example:
sql1: `select 'abc' from t group by 'abc'`
is not equivalent to
sql2: `select 'abc' from t`
sql3: `select 'abc', sum(a) from t group by 'abc'`
is not equivalent to
sql4: `select 1, sum(a) from t`
(when t is empty, sql3 returns 0 tuple, sql4 return 1 tuple)
We need to keep some constant columns if all groupingExpr are constant.
Consider sql5 `select a from (select "abc" as a, 'def' as b) T group by b,
a;` if the constant column `a` is in select list, this column should not be
removed. sql5 is transformed to
sql6 `select a from (select "abc" as a, 'def' as b) T group by a;`
(cherry picked from commit a2b9b9edd72d70fed4cd76c571ee5b736493e3a7)
# Proposed changes
Issue Number: close #xxx
## Problem summary
Describe your changes.
## Checklist(Required)
* [ ] Does it affect the original behavior
* [ ] Has unit tests been added
* [ ] Has document been added or modified
* [ ] Does it need to update dependencies
* [ ] Is this PR support rollback (If NO, please explain WHY)
## Further comments
If this is a relatively large or complex change, kick off the discussion at
[d...@doris.apache.org](mailto:d...@doris.apache.org) by explaining why you
chose the solution you did and what alternatives you considered, etc...
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: commits-unsubscr...@doris.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscr...@doris.apache.org
For additional commands, e-mail: commits-h...@doris.apache.org
