Tom Lane escribió:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Maybe it would make more sense to try to reorder the fsync calls
> > instead.
>
> Reorder to what, though? You still have the problem that we don't know
> much about the physical layout on-disk.
Well, to block numbers as a first step.
However, this reminds me that sometimes we take the block-at-a-time
extension policy too seriously. We had a customer that had a
performance problem because they were inserting lots of data to TOAST
tables, causing very frequent extensions. I kept wondering whether an
allocation policy that allocated several new blocks at a time could be
useful (but I didn't try it). This would also alleviate fragmentation,
thus helping the physical layout be more similar to logical block
numbers.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support