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!
Amin <amin.fallahi@gmail.com> writes:
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.
Sure you do. The existing code, eg in selfuncs.c, does it about like
this:
RangeTblEntry *rte = planner_rt_fetch(rel->relid, root);
Assert(rte->rtekind == RTE_RELATION);
relid = rte->relid;
Assert(relid != InvalidOid);
...
vardata.statsTuple = SearchSysCache3(STATRELATTINH,
ObjectIdGetDatum(relid),
Int16GetDatum(colnum),
BoolGetDatum(rte->inh));
This is maybe a bit confusing, in that rel->relid is a range
table index but rte->relid is an OID.
FWIW, I seriously doubt that the numbers kept by the pg_stat mechanisms
are what you want for query planning purposes.
regards, tom lane