From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Amin <amin(dot)fallahi(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Get relid for a relation |
Date: | 2023-01-13 14:45:26 |
Message-ID: | 1674576.1673621126@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Amin <amin(dot)fallahi(at)gmail(dot)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
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