Multi plan for the same query is allowed, but which one is used is undefined.

[lemontree-mxh]

The current implementation allows us create multi plan for the same query, and allow us enable all of them. and letter which one is choose is not well defined in looup_plan_by_query_hash.

How about to add a new index

create unique index sr_plans_query_hash_idx on sr_plan(query_hash) where (enable=true);