diff --git a/README.md b/README.md index f4831e5..fd45c19 100644 --- a/README.md +++ b/README.md @@ -171,6 +171,15 @@ And this time, the specific configuration is applied. Caveats -------- +`pg_query_settings` doesn't work well with **prepared queries**. More specifically: +for a given parameter `P`, if the generic plan is selected, and if the executor +needs to fetch the value of `P`, then it won't get the value specified in the +`pgqs_config` table. For example, the executor fetches the value of `work_mem` +in order to decide whether to perform an in-memory sort, while the parameter +`max_parallel_workers_per_gather` is only used during the planification stage, +so `pg_query_settings` only works for this last example. +This will be fixed in future releases. + Enabling this extension might have a performance impact on any workloads with a high number of fast queries, as it slighlty increases the time taken to compute the query plan. The more entries in the table, the greater the