Re: pg_plan_advice

Robert Haas <robertmhaas(at)gmail(dot)com> 于2026年4月16日周四 03:47写道：
>
> On Wed, Apr 15, 2026 at 6:30 AM Tender Wang <tndrwang(at)gmail(dot)com> wrote:
> > In the plan_showdown phase, in pgpa_qf_add_plan_rtis(), we can add 7,
> > 5, and 3 to qf->relids.
> > It seems difficult to add "6" to qf->relids when walking through the
> > plan tree.(Maybe have an easy way, I don't know too much
> > pg_plan_advice related code).
>
> Thanks for looking through this. sj_unique_rtis is actually not set
> from the plan tree walk, but based on the calls to
> pgpa_join_path_setup that occur during planning, so it makes sense
> that the join RTI crept in there. I'm guessing that this is another
> place that needs a call to pgpa_filter_out_join_relids -- I've had a
> few of those bugs already.
I try a quick fix as follow:
diff --git a/contrib/pg_plan_advice/pgpa_planner.c
b/contrib/pg_plan_advice/pgpa_planner.c
index 72ef3230abc..971f301e950 100644
--- a/contrib/pg_plan_advice/pgpa_planner.c
+++ b/contrib/pg_plan_advice/pgpa_planner.c
@@ -541,6 +541,7 @@ pgpa_join_path_setup(PlannerInfo *root, RelOptInfo *joinrel,
{
pgpa_planner_state *pps;
RelOptInfo *uniquerel;
+ Bitmapset *relids;

uniquerel = jointype == JOIN_UNIQUE_OUTER ? outerrel : innerrel;
pps = GetPlannerGlobalExtensionState(root->glob,
planner_extension_id);
@@ -562,8 +563,11 @@ pgpa_join_path_setup(PlannerInfo *root,
RelOptInfo *joinrel,
oldcontext = MemoryContextSwitchTo(pps->mcxt);
proot = pgpa_planner_get_proot(pps, root);
if (!list_member(proot->sj_unique_rels,
uniquerel->relids))
+ {
+ relids =
pgpa_filter_out_join_relids(uniquerel->relids, root->parse->rtable);
proot->sj_unique_rels =
lappend(proot->sj_unique_rels,
-
bms_copy(uniquerel->relids));
+
bms_copy(relids));
+ }
MemoryContextSwitchTo(oldcontext);
}
}

postgres=# LOAD 'pg_plan_advice';
LOAD
postgres=# EXPLAIN (COSTS OFF, PLAN_ADVICE)SELECT 1 FROM t1 WHERE EXISTS
(SELECT 1 FROM
(SELECT 1 FROM
(SELECT 1) LEFT JOIN t2 ON true),
t2 WHERE a = b);
QUERY PLAN
---------------------------------------------------
Hash Join
Hash Cond: (t1.a = t2.b)
-> Seq Scan on t1
-> Hash
-> HashAggregate
Group Key: t2.b
-> Nested Loop
-> Nested Loop Left Join
-> Result
-> Seq Scan on t2 t2_1
-> Materialize
-> Seq Scan on t2
Generated Plan Advice:
JOIN_ORDER(t1 ("*RESULT*" t2#2 t2))
NESTED_LOOP_PLAIN(t2#2)
NESTED_LOOP_MATERIALIZE(t2)
HASH_JOIN((t2 t2#2 "*RESULT*"))
SEQ_SCAN(t1 t2#2 t2)
SEMIJOIN_UNIQUE((t2 t2#2 "*RESULT*"))
NO_GATHER(t1 t2 t2#2 "*RESULT*")
(20 rows)

--
Thanks,
Tender Wang