On 3/18/24 16:19, Melanie Plageman wrote: > On Mon, Mar 18, 2024 at 02:10:28PM +0200, Heikki Linnakangas wrote: >> On 14/02/2024 21:42, Andres Freund wrote: >>> On 2024-02-13 18:11:25 -0500, Melanie Plageman wrote: >>>> patch 0004 is, I think, a bug fix. see [2]. >>> >>> I'd not quite call it a bugfix, it's not like it leads to wrong >>> behaviour. Seems more like an optimization. But whatever :) >> >> It sure looks like bug to me, albeit a very minor one. Certainly not an >> optimization, it doesn't affect performance in any way, only what EXPLAIN >> reports. So committed and backported that to all supported branches. > > I've attached v7 rebased over this commit. >
I've started a new set of benchmarks with v7 (on top of f69319f2f1), but unfortunately that results in about 15% of the queries failing with: ERROR: prefetch and main iterators are out of sync Reproducing it is pretty simple (at least on my laptop). Simply apply 0001-0011, and then do this: ====================================================================== create table test_table (a bigint, b bigint, c text) with (fillfactor = 25); insert into test_table select 10000 * random(), i, md5(random()::text) from generate_series(1, 1000000) s(i); create index on test_table(a); vacuum analyze ; checkpoint; set work_mem = '128kB'; set effective_io_concurrency = 8; set random_page_cost = 2; set max_parallel_workers_per_gather = 0; explain select * from test_table where a >= 1 and a <= 512; explain analyze select * from test_table where a >= 1 and a <= 512; ERROR: prefetch and main iterators are out of sync ====================================================================== I haven't investigated this, but it seems to get broken by this patch: v7-0009-Make-table_scan_bitmap_next_block-async-friendly.patch I wonder if there are some additional changes aside from the rebase. regards -- Tomas Vondra EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
