On Wednesday, January 21st, 2026 at 17:28, Tom Lane <[email protected]> wrote:
> > > Nicolas Seinlet [email protected] writes: > > > We issue queries like : > > SELECT model, res_id FROM ir_model_data WHERE module='base' AND > > name='public_user'; > > > With 1.0 extension, the query is planned with a matching btree index: > > "ir_model_data_module_name_uniq_index" UNIQUE, btree (module, name) > > > With 1.6 extension, the query is planned with a gist index: > > "ir_model_data_name_idx2" gist (name gist_trgm_ops) > > > 1.0 extension executes the query in 0.1ms, while 1.6 in 100ms > > > It seems quite odd that the planner would prefer an index > using only one of the two clauses. It must be concluding that > the gist indexscan will be cheaper, but it's hard to see why > that would be. > > Could we see EXPLAIN ANALYZE output for those two cases? > Are the statistics for the table up-to-date? > > regards, tom lane That table is not that much updated, so we could expect the statistics are quite up-to-date, especially because our analyse trigger parameters are quite aggressive. But, to ensure they are decently correct, I'll include a vacuum analyse in my test. With pg_trgm=1.5: QUERY PLAN ----------- Index Scan using ir_model_data_module_name_uniq_index on ir_model_data (cost=0.56..2.58 rows=1 width=17) (actual time=0.027..0.028 rows=1 loops=1) Index Cond: (((module)::text = 'base'::text) AND ((name)::text = 'public_user'::text)) Planning Time: 0.093 ms Execution Time: 0.050 ms (4 rows) With pg_trgm=1.6: QUERY PLAN ---------- Index Scan using ir_model_data_name_idx2 on ir_model_data (cost=0.42..2.44 rows=1 width=17) (actual time=8403.936..9847.983 rows=1 loops=1) Index Cond: ((name)::text = 'public_user'::text) Rows Removed by Index Recheck: 10 Filter: ((module)::text = 'base'::text) Planning Time: 1.564 ms Execution Time: 9848.027 ms (6 rows) For the tests, the random_page_cost=1. Let's try with random_page_cost=2 QUERY PLAN ---------- Index Scan using ir_model_data_name_idx2 on ir_model_data (cost=0.42..4.44 rows=1 width=17) (actual time=106.136..191.606 rows=1 loops=1) Index Cond: ((name)::text = 'public_user'::text) Rows Removed by Index Recheck: 10 Filter: ((module)::text = 'base'::text) Planning Time: 0.096 ms Execution Time: 191.623 ms (6 rows) And finally, after a vacuum analyse and set random_page_cost to 1: QUERY PLAN ----------- Index Scan using ir_model_data_name_idx2 on ir_model_data (cost=0.42..4.44 rows=1 width=17) (actual time=104.866..189.119 rows=1 loops=1) Index Cond: ((name)::text = 'public_user'::text) Rows Removed by Index Recheck: 10 Filter: ((module)::text = 'base'::text) Planning Time: 0.352 ms Execution Time: 189.134 ms (6 rows) Thanks for all, Nicolas.
