On 2020/08/04 19:21, Stelios Sfakianakis wrote: > Thank you again, I have another question in order to make sure I have a clear understanding: > > >> On 4 Aug 2020, at 11:24, Ian Lawrence Barwick <barwick@xxxxxxxxx> wrote: >> >> The hash table is specific to each running backend so will only be >> accessed by that process. >> >> Pre-loading a shared library just gives the library an opportunity to >> set up shared memory etc. You can always try adding one of the FDW >> libraries to "shared_preload_libraries" and see what happens >> (theoretically nothing). >> > > My impression was that since each client (e.g. libpq) connection results in the creation of a Postgres process in the backend (https://www.postgresql.org/developer/backend/) then this (mysql) "connection pool" hash table is not global per se and shared among the different client / users sessions. Correct, the connections are specific to each individual backend. > But that defeats the purpose, no? The purpose is to cache connections within the session, to avoid the overhead of reconnecting to the remote server each time a query for that server is issued in that session. Regards Ian Barwick -- Ian Barwick https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
