primary_routing_query_pattern_list is appended instead of overwritten on reload

[0713seki-stack]

Description:
In Pgpool-II 4.4.15, when updating primary_routing_query_pattern_list in pgpool.conf and executing systemctl reload (SIGHUP), the new patterns are appended to the existing list rather than replacing them.

Steps to reproduce:

Set primary_routing_query_pattern_list = 'SELECT 1' in pgpool.conf and start Pgpool-II.

Change it to primary_routing_query_pattern_list = 'SELECT 2' and execute pgpool reload.

Pgpool-II now holds both 'SELECT 1' and 'SELECT 2' in its internal list.

Impact:

Deleted or modified patterns remain active.

Memory consumption increases with every reload.

Duplicate patterns lead to redundant evaluation logic.

Environment:

Pgpool-II version: 4.4.15

OS: RHEL8.10