Re: pg11.1: dsa_area could not attach to segment - Mailing list pgsql-hackers

I should have included query plan for the query which caused the "could not
find free pages" error.

This is a contrived query which I made up to try to exercise/stress bitmap
scans based on Thomas's working hypothesis for this error/bug.  This seems to
be easier to hit than the other error ("could not attach to segment") - a loop
around this query has run into "free pages" several times today.

explain (analyze,costs off,timing off) SELECT * FROM eric_enodeb_metrics WHERE start_time>='2017-10-01' AND
(site_id<1900OR site_id>2700)
 

 Gather (actual rows=82257 loops=1)
   Workers Planned: 3
   Workers Launched: 3
   ->  Parallel Append (actual rows=20564 loops=4)
         ->  Parallel Bitmap Heap Scan on eric_enodeb_201901 (actual rows=6366 loops=4)
               Recheck Cond: ((site_id < 1900) OR (site_id > 2700))
               Filter: (start_time >= '2017-10-01 00:00:00-04'::timestamp with time zone)
               Heap Blocks: exact=2549
               ->  BitmapOr (actual rows=0 loops=1)
                     ->  Bitmap Index Scan on eric_enodeb_201901_site_idx (actual rows=0 loops=1)
                           Index Cond: (site_id < 1900)
                     ->  Bitmap Index Scan on eric_enodeb_201901_site_idx (actual rows=25463 loops=1)
                           Index Cond: (site_id > 2700)
         ->  Parallel Bitmap Heap Scan on eric_enodeb_201810 (actual rows=15402 loops=1)
               Recheck Cond: ((site_id < 1900) OR (site_id > 2700))
               Filter: (start_time >= '2017-10-01 00:00:00-04'::timestamp with time zone)
               ->  BitmapOr (actual rows=0 loops=1)
                     ->  Bitmap Index Scan on eric_enodeb_201810_site_idx (actual rows=0 loops=1)
                           Index Cond: (site_id < 1900)
                     ->  Bitmap Index Scan on eric_enodeb_201810_site_idx (actual rows=15402 loops=1)
                           Index Cond: (site_id > 2700)
         ->  Parallel Bitmap Heap Scan on eric_enodeb_201812 (actual rows=14866 loops=1)
               Recheck Cond: ((site_id < 1900) OR (site_id > 2700))
               Filter: (start_time >= '2017-10-01 00:00:00-04'::timestamp with time zone)
               ->  BitmapOr (actual rows=0 loops=1)
                     ->  Bitmap Index Scan on eric_enodeb_201812_site_idx (actual rows=0 loops=1)
                           Index Cond: (site_id < 1900)
                     ->  Bitmap Index Scan on eric_enodeb_201812_site_idx (actual rows=14866 loops=1)
                           Index Cond: (site_id > 2700)
         ->  Parallel Bitmap Heap Scan on eric_enodeb_201811 (actual rows=7204 loops=2)
               Recheck Cond: ((site_id < 1900) OR (site_id > 2700))
               Filter: (start_time >= '2017-10-01 00:00:00-04'::timestamp with time zone)
               Heap Blocks: exact=7372
               ->  BitmapOr (actual rows=0 loops=1)
                     ->  Bitmap Index Scan on eric_enodeb_201811_site_idx (actual rows=0 loops=1)
                           Index Cond: (site_id < 1900)
                     ->  Bitmap Index Scan on eric_enodeb_201811_site_idx (actual rows=14408 loops=1)
                           Index Cond: (site_id > 2700)
         ->  Parallel Bitmap Heap Scan on eric_enodeb_201902 (actual rows=5128 loops=1)
               Recheck Cond: ((site_id < 1900) OR (site_id > 2700))
               Filter: (start_time >= '2017-10-01 00:00:00-04'::timestamp with time zone)
               Heap Blocks: exact=3374
               ->  BitmapOr (actual rows=0 loops=1)
                     ->  Bitmap Index Scan on eric_enodeb_201902_site_idx (actual rows=0 loops=1)
                           Index Cond: (site_id < 1900)
                     ->  Bitmap Index Scan on eric_enodeb_201902_site_idx (actual rows=5128 loops=1)
                           Index Cond: (site_id > 2700)
         [...]

Justin