Get relid for a relation

Hi,

In CustomScan cost estimator, where PlannerInfo and RelOptInfo are passed,
I want to get access to the relation stats (for example pg_stat_all_tables)
by calling pg_stat_fetch_stat_tabentry(). However, I don't have access to
relid to pass to this function. For a sample relation, when I hardcode the
relid (for example 16385), it works. However, RelOptInfo->relid is always 1
(for whatever relation the query is scanning). Why this happens and how to
get access to the correct relid (16385) as in pg_stat_all_tables?

Thank you!