Re: POC: converting Lists into arrays

Hi,

On 2019-02-25 17:55:46 -0800, Andres Freund wrote:
> Hm, I wonder if that's necessary / whether we can just work around user
> visible breakage at a small cost. I think I'm mostly concerned with two
> allocations for the very common case of small (1-3 entries) lists. We
> could just allocate the first array together with the header, and not
> free that if the list grows beyond that point. That'd mean we'd only do
> separate allocations once they actually amortize over a number of
> allocations.

Btw, if we actually were going to go for always allocating header + data
together (and thus incuring the problems you mention upthread), we ought
to store the members as a FLEXIBLE_ARRAY_MEMBER together with the
list. Probably not worth it, but reducing the number of pointer
indirections for "list" accesses would be quite neat.

Greetings,

Andres Freund