On Wed, Apr 17, 2013 at 4:26 AM, François Beausoleil <francois@xxxxxxxxxxx> wrote:
Insert on public.persona_followers (cost=139261.12..20483497.65 rows=6256498 width=16) (actual time=4729255.535..4729255.535 rows=0 loops=1)
Buffers: shared hit=33135295 read=4776921
-> Subquery Scan on t1 (cost=139261.12..20483497.65 rows=6256498 width=16) (actual time=562265.156..578844.999 rows=6819520 loops=1)
It looks like 12% of the time is being spent figuring out what rows to insert, and 88% actually doing the insertions.
So I think that index maintenance is killing you. You could try adding a sort to your select so that rows are inserted in index order, or inserting in batches in which the batches are partitioned by service_id (which is almost the same thing as sorting, since service_id is the lead column)
Cheers,
Jeff
