Re: Optimizing Read-Only Scalability

Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, May 14, 2009 at 1:28 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> GetSnapshotData doesn't take an exclusive lock. �Neither does start or
>> end of a read-only transaction. �AFAIK there is no reason, and certainly
>> no shred of experimental evidence, to think that ProcArrayLock
>> contention is the bottleneck for read-only scenarios.

> I think Simon's point was that it is O(n) rather than O(1), not that
> it took an exclusive lock.

I think my point was that there's no evidence that GetSnapshotData
is where the scalability issue is.  Without some evidence there's no
point in kluging it up.
        regards, tom lane