Re: open/lseek overhead with many partitions (including with "fasterpartitioning pruning")

Hi Justin.

On 2018/04/04 4:46, Justin Pryzby wrote:
> TLDR: even with "faster pruning" patch, pg11dev open()+lseek() every file
> backing every table being queried, even for those partitions eventually
> "excluded".

That's expected.  The faster pruning patch doesn't change the behavior
with respect to when the partitions' files are open()'d, which at this
point is still *before* the pruning occurs.  It just switches the method
of pruning to a faster one, whereby instead of pruning each partition
one-by-one using constraint exclusion, we only look at the parent's
partition descriptor to exclude partitions that don't satisfy the query.

Thanks,
Amit