| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Yasir <yasir(dot)hussain(dot)shah(at)gmail(dot)com> |
| Cc: | Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Alias of VALUES RTE in explain plan |
| Date: | 2024-10-25 19:21:54 |
| Message-ID: | 3037675.1729884114@sss.pgh.pa.us |
| Views: | Whole Thread | Raw Message | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
I wrote:
> However ... I don't like this implementation, not even a little
> bit.
I forgot to mention a third problem, which is that reassigning the
alias during subquery pullup means it doesn't happen if subquery
pullup doesn't happen. As an example, with your patch:
regression=# explain verbose select * from (values (1), (2)) v(x);
QUERY PLAN
----------------------------------------------------
Values Scan on v (cost=0.00..0.03 rows=2 width=4)
Output: v.x
(2 rows)
regression=# explain verbose select * from (values (1), (random())) v(x);
QUERY PLAN
-------------------------------------------------------------
Values Scan on "*VALUES*" (cost=0.00..0.03 rows=2 width=8)
Output: "*VALUES*".column1
(2 rows)
That's because the volatile function prevents subquery flattening.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Masahiko Sawada | 2024-10-25 19:25:59 | Re: Parallel heap vacuum |
| Previous Message | Sergey Sargsyan | 2024-10-25 18:32:55 | Re: CREATE INDEX CONCURRENTLY on partitioned index |