Re: Scalability in postgres

On Fri, Jun 5, 2009 at 1:02 PM, Greg Smith<gsmith(at)gregsmith(dot)com> wrote:
> On Fri, 5 Jun 2009, Mark Mielke wrote:
>> I disagree that profiling trumps theory every time.
> That's an interesting theory.  Unfortunately, profiling shows it doesn't
> work that way.

I had a laugh when I read this, but I can see someone being offended
by it. Hopefully no one took it that way.

> Let's see if I can summarize the state of things a bit better here:
>
> 1) PostgreSQL stops working as efficiently with >1000 active connections
>
> 2) Profiling suggests the first barrier that needs to be resolved to fix
> that is how the snapshots needed to support MVCC are derived
>
> 3) There are multiple patches around that aim to improve that specific
> situation, but only being tested aggressively by one contributor so far
> (that I'm aware of)

I am actually aware of only two forays into this area that have been
reduced to code. I am pretty much convinced that Jignesh's
wake-all-waiters patch is fundamentally - dare I say theoretically -
unsound, however much it may improve performance for his particular
workload. The other is Simon's patch which AIUI is a fast-path for
the case where nothing has changed. Are you aware of any others?

Thanks for the summary.

...Robert