Re: synchronous commit vs. hint bits

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>

To: Robert Haas <robertmhaas@gmail.com>

Cc: pgsql-hackers@postgresql.org

Date: 2011-11-07T15:12:08Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Allow hint bits to be set sooner for temporary and unlogged tables.
- 53f1ca59b587 9.2.0 cited

Robert Haas <robertmhaas@gmail.com> writes:
> SetHintBits() can't set HEAP_XMIN_COMMITTED or HEAP_XMAX_COMMITTED
> hints until the commit record has been durably flushed to disk.  It
> turns out that can cause a major performance regression on systems
> with many CPU cores.

It seems to me that you've jumped to proposing solutions before you know
where the problem actually is --- or at least, if you do know where the
problem is, you didn't explain it.  Is the cost in repeating clog
lookups, or in testing to determine whether it's safe to set the bit
yet, or is it contention associated with one or the other of those?

			regards, tom lane