create extension tsm_system_rows ; create schema s1; create function s1.system_rows(internal) returns void language c as 'tsm_system_rows.so', 'tsm_system_rows_handler'; set search_path to s1,public,pg_catalog; select count(*) from pg_class tablesample system_rows(0); ERROR: function system_rows must return type tsm_handler LINE 1: select count(*) from pg_class tablesample system_rows(0);
The above is a denial-of-service due to our decision to lookup handler functions by name regardless of return type and consider it an error if a function with the wrong return type shows up (in particular, even though one with the correct signature exists and otherwise would have been found).
The attached POC fixes this by allowing callers to also specify the OID of the handler type as part of their function lookup criteria. Tablesample is fixed to use this new call though possibly others exist. I'm not particularly fond of what I ended up with naming conventions but figure it's good enough for now.
