| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tomas Vondra <tv(at)fuzzy(dot)cz>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Poor memory context performance in large hash joins |
| Date: | 2017-02-24 06:59:01 |
| Message-ID: | 8808.1487919541@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-02-23 17:28:26 -0500, Tom Lane wrote:
>> Maybe it's time to convert that to a doubly-linked list.
> Yes, I do think so. Given that we only have that for full blocks, not
> for small chunks, the cost seems neglegible.
> That would also, partially, address the performance issue
> http://archives.postgresql.org/message-id/d15dff83-0b37-28ed-0809-95a5cc7292ad%402ndquadrant.com
> addresses, in a more realistically backpatchable manner.
Yeah, I was wondering if we could get away with back-patching such a
change. In principle, nothing outside aset.c should know what's in the
header of an AllocBlock, but ...
> Jeff, do you have a handy demonstrator?
A solid test case would definitely help to convince people that it was
worth taking some risk here.
regards, tom lane
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