On Thu, Jul 23, 2015 at 9:58 AM, Laurent Debacker <[email protected]> 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
