Re: Wrong results with grouping sets

Richard Guo <guofenglinux@gmail.com>

From: Richard Guo <guofenglinux@gmail.com>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2024-05-23T07:30:43Z

Lists: pgsql-hackers

Commits

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Remove the RTE_GROUP RTE if we drop the groupClause
- ffe12d1d22e7 18.0 landed
Mark expressions nullable by grouping sets
- f5050f795aea 18.0 landed
Introduce an RTE for the grouping step
- 247dea89f761 18.0 landed

Attachments

v5-0001-Introduce-a-RTE-for-the-grouping-step.patch (application/octet-stream) patch v5-0001

On Fri, May 17, 2024 at 5:41 PM Richard Guo <guofenglinux@gmail.com> wrote:

> I've spent some more time on this patch, and now it passes all the
> regression tests.  But I had to hack explain.c and ruleutils.c to make
> the varprefix stuff work as it did before, which is not great.
>

I've realized that I made a mistake in the v4 patch: If there are join
alias vars in the targetlist and HAVING clause, we should first flatten
them before replacing the grouped variables involved there with
grouping-RTE Vars.  To fix this issue, I decide to merge the newly added
function substitute_group_exprs into check_ungrouped_columns by changing
check_ungrouped_columns to also perform the replacement, which is Tom's
initial suggestion I think.

Now it seems that 'check_ungrouped_columns' is no longer an appropriate
name for the function.  So I rename it to 'substitute_grouped_columns'.
But I'm open to other names if there are any suggestions.

I've also worked on the comments.

Thanks
Richard