I have used pg_prewarm during some of work related to Buffer Management and other performance related work. It is quite useful utility. +1 for reviving this patch for 9.4
Any other votes?
We've had to manually code something that runs EXPLAIN ANALYZE SELECT * from a bunch of tables to warm our caches after a restart, but there's numerous flaws to that approach obviously.
Unfortunately, what we really need to warm isn't the PG buffers, it's the FS cache, which I suspect this won't help. But I still see where just pg_buffers would be useful for a lot of folks, so +1.
Since it doesn't use directIO, you can't warm the PG buffers without also warming FS cache as a side effect. That is why I like 'buffer' as the default--if the data fits in shared_buffers, it warm those, otherwise it at least warms the FS. If you want to only warm the FS cache, you can use either the 'prefetch' or 'read' modes instead.
