| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | David Fetter <david(at)fetter(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Jeff Davis <pgsql(at)j-davis(dot)com> |
| Subject: | Re: Spilling hashed SetOps and aggregates to disk |
| Date: | 2018-06-06 14:01:29 |
| Message-ID: | 20180606140129.ymghte3rtv33d5ad@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2018-06-06 15:58:16 +0200, Tomas Vondra wrote:
> The other issue is that serialize/deserialize is only a part of a problem -
> you also need to know how to do "combine", and not all aggregates can do
> that ... (certainly not in universal way).
There are several schemes where only serialize/deserialize are needed,
no? There are a number of fairly sensible schemes where there won't be
multiple transition values for the same group, no?
Greetings,
Andres Freund
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