Re: [HACKERS] Poor memory context performance in large hash joins

Andres Freund <andres@anarazel.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