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 |
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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
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