| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
| Cc: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, PostgreSQL <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Varying results when using merge joins over postgres_fdw vs hash joins |
| Date: | 2017-09-20 15:40:02 |
| Message-ID: | CAH2-Wzn=At0vRRButghoSutCgEX8NTG76tmSN-0R92ZJPR0Teg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Sep 20, 2017 at 2:06 AM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
> In this case, both tables use same collation while comparing the rows,
> so result is different from the merge join result. Hash join executed
> on local server and the same executed on foreign server (by importing
> local table to the foreign server) would also differ.
Not really, because collatable types like text have the same equality
behavior, regardless of collation. (I would prefer it if they didn't
in at least some cases, but we don't have case insensitive collations
yet.)
I think that Corey describes a user hostile behavior. I feel that we
should try to do better here.
--
Peter Geoghegan
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