Re: Get relid for a relation

[Tom Lane]

Amin  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

Get relid for a relation

[Amin]

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!