Re: misleading error message in ProcessUtilitySlow T_CreateStatsStmt

On Thu, Nov 13, 2025 at 5:41 PM Álvaro Herrera <alvherre(at)kurilemu(dot)de> wrote:
>
> On 2025-Nov-13, jian he wrote:
>
> > @@ -15658,10 +15658,19 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
> > querytree_list = list_concat(querytree_list, afterStmts);
> > }
> > else if (IsA(stmt, CreateStatsStmt))
> > + {
> > + RangeTblEntry *rte;
> > + CreateStatsStmt *ss = castNode(CreateStatsStmt, stmt);
> > +
> > + rte = makeNode(RangeTblEntry);
> > + rte->rtekind = RTE_RELATION;
> > + rte->relid = oldRelId;
> > + rte->rellockmode = ShareUpdateExclusiveLock;
> > + ss->rtable = list_make1(rte);
> > +
> > querytree_list = lappend(querytree_list,
> > - transformStatsStmt(oldRelId,
> > - (CreateStatsStmt *) stmt,
> > - cmd));
> > + transformStatsStmt(ss, cmd));
> > + }
> > else
> > querytree_list = lappend(querytree_list, stmt);
> > }
>
> Hmm, how would this part here work in the hypothetical world where a
> stats object references multiple relations?
>
hi.

per
https://www.postgresql.org/docs/current/catalog-pg-statistic-ext.html
extended statistics either based on column name or expression.

If based on column name, imagine a simple case:
CREATE STATISTICS ON a FROM t1,t2;
pg_statistic_ext obviously needs another column to store other relation oids.
in this case, we can use AlteredTableInfo->changedStatisticsOids to lookup
catalog table pg_statistic_ext to find out the associated relation oids

If extended statistics is based on expression, imagine a simple case:
CREATE STATISTICS on (t1.a + t2.a) from t1, t2;
ruleutils.c can not cope with expressions like: "(t1.a + t2.a)",
so we have to wrap the expression into a Query Node, store it in
pg_statistic_ext.stxexprs.

If pg_statistic_ext does not contain all associated relation
OIDs, all these pg_get_statisticsobjdef_expressions won't work

pg_statistic_ext should contain all associated relation OIDs, in my opinion. If
pg_statistic_ext does store all related relation OIDs, then the potential issue
you mentioned above should be solvable.

--
jian
https://www.enterprisedb.com/