Thanks Jeff! That makes sense indeed.
I'm a bit surprised a COUNT(1) would need a bitmap heap scan since we know the row count from the index, but okay.
Have a nice day,
Laurent
On Thu, Jul 23, 2015 at 8:04 PM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote:
On Thu, Jul 23, 2015 at 9:58 AM, Laurent Debacker <debackerl@xxxxxxxxx> wrote:Hi,I have read that GIN indexes don't require a recheck cond for full text search as long as work_mem is big enough, otherwise you get lossy blocks, and the recheck cond.In my case, I have no lossy blocks (from what I could tell), but I do have a recheck...EXPLAIN (ANALYZE, BUFFERS) SELECT COUNT(1) FROM enterprises WHERE fts @@ 'activ'::tsquery"Aggregate (cost=264555.07..264555.08 rows=1 width=0) (actual time=25813.920..25813.921 rows=1 loops=1)"" Buffers: shared hit=1 read=178192"" -> Bitmap Heap Scan on enterprises (cost=5004.86..263202.54 rows=541014 width=0) (actual time=170.546..25663.048 rows=528376 loops=1)"" Recheck Cond: (fts @@ '''activ'''::tsquery)"" Heap Blocks: exact=178096"" Buffers: shared hit=1 read=178192"" -> Bitmap Index Scan on enterprises_fts_idx (cost=0.00..4869.61 rows=541014 width=0) (actual time=120.214..120.214 rows=528376 loops=1)"" Index Cond: (fts @@ '''activ'''::tsquery)"" Buffers: shared hit=1 read=96""Planning time: 2.383 ms""Execution time: 25824.476 ms"Any advice would be greatly appreciated. I'm running PostgreSQL 9.4.1.The Recheck Cond line is a plan-time piece of info, not a run-time piece. It only tells you what condition is going to be rechecked if a recheck is found to be necessary.It doesn't indicate how many times it was found it to be necessary to do the recheck. Presumably that number was zero.Cheers,Jeff
