On Tue, 8 Apr 2025 at 12:21, Ryohei Takahashi (Fujitsu) <r.takahash...@fujitsu.com> wrote: > By using Statistics Import and Export feature, is it possible to achieve the > above request by following procedure? > (1) Export the statistics from production environment by using pg_dump > --statistics-only. > (2) On the staging environment, set the autovacuum related parameters to > prevent autovacuum from running. > (3) Import the statistics to staging environment by using the result of (1).
You could certainly test the performance, but this method isn't guaranteed to give meaningful results just because the table stats match. One important thing to remember is that the planner also looks at the *actual size* of the relation and takes that into account when scaling the statistics (see table_block_relation_estimate_size() in tableam.c). If the table sizes don't match between the two servers then there's no guarantees the planner will produce the same plan. Also, there might be other subtleties regarding OIDs of indexes which are not guaranteed to be the same after dump/restore. Given some fuzzily close enough cost estimates (See add_path() and compare_path_costs_fuzzily()), it is possible a plan would switch to using another index if sorting the indexes by their OIDs didn't match on each server. The chances of that might be fairly small, but not zero. You'd also need to ensure the configs are the same in terms of GUCs that are used for costs. You could probably use get_relation_info_hook to overwrite the sizes and make sure the indexes are in the same order, etc. David
