Re: slow bitmap heap scans on pg 9.2

On 13-04-10 02:06 PM, Jeff Janes wrote:
> On Wed, Apr 10, 2013 at 6:49 AM, Steve Singer <ssinger(at)ca(dot)afilias(dot)info
> <mailto:ssinger(at)ca(dot)afilias(dot)info>> wrote:
>

> I think the index recheck means your bitmap is overflowing (i.e. needing
> more space than work_mem) and so keeping only the pages which have at
> least one match, which means all rows in those pages need to be
> rechecked. How many rows does the table have? You might be essentially
> doing a seq scan, but with the additional overhead of the bitmap
> machinery. Could you do "explain (analyze,buffers)", preferably with
> track_io_timing set to on?
>

table_b has 1,530,710,469 rows

Attached is the output with track_io_timings and buffers.

> Cheers,
>
> Jeff