| From: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com>, sean(dot)johnston(at)edgeintelligence(dot)com, Postgres-Bugs <pgsql-bugs(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: [BUGS] BUG #14890: Error grouping by same column twice using FDW |
| Date: | 2017-11-17 12:09:32 |
| Message-ID: | CAFjFpRfJBZT6Pjq6xQ5jzn9gsuMXtuqn+8=BnTUG7vAdb6Litw@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Sat, Nov 11, 2017 at 12:14 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> As you say, we can probably get away without that as long as we don't push
> mutable grouping expressions ... but just because we think a grouping
> expression is immutable at our end doesn't necessarily mean that it is at
> the far end.
Well, I thought of that case but then we may have problems without
GROUP BY. use_physical_tlist() doesn't list ForeignScan as an
exception. deparseTargetList() constructs the tlist based on
attrs_used, which doesn't know if the same column was repeated in the
SELECT clause. build_tlist_to_deparse() flattens the tlist to be
deparsed. I think the assumption is that the user won't use immutable
expression as a column.
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company
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