Re: Bogus EXPLAIN results with column aliases for mismatched partitions

I wrote:
> Etsuro Fujita <etsuro.fujita@gmail.com> writes:
>> On Mon, Dec 2, 2019 at 6:34 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> BTW, the existing code always schema-qualifies the relation names,
>>> on the rather lame grounds that it's producing the string without
>>> knowing whether EXPLAIN VERBOSE will be specified.  In this code,
>>> the verbose flag is available so it would be trivial to make the
>>> output conform to EXPLAIN's normal policy.  I didn't change that
>>> here because there'd be a bunch more test output diffs of no
>>> intellectual interest.  Should we change it, or leave well enough
>>> alone?

>> I think it would be better to keep that as-is because otherwise, in
>> case of a foreign join or aggregate, EXPLAIN without the VERBOSE
>> option won't show any information about foreign tables involved in
>> that foreign join or aggregate, which isn't useful for users.

> No, I'm just talking about dropping the schema-qualification of table
> names when !es->verbose, not removing the Relations: output altogether.
> That would be more consistent with the rest of EXPLAIN's output.

Concretely, I'm thinking of the attached (on top of the other patch,
which I just pushed).  This agrees exactly with what ExplainTargetRel
does for regular scans.

One could make an argument that we should schema-qualify, regardless
of the "verbose" flag, if the output format isn't EXPLAIN_FORMAT_TEXT.
That would reduce the amount of variability that plan analysis tools
have to cope with.  However, ExplainTargetRel itself doesn't provide
the schema in non-verbose mode.  Maybe it should, ie we should change
it like

         case T_ModifyTable:
             /* Assert it's on a real relation */
             Assert(rte->rtekind == RTE_RELATION);
             objectname = get_rel_name(rte->relid);
-            if (es->verbose)
+            if (es->verbose || es->format != EXPLAIN_FORMAT_TEXT)
                 namespace = get_namespace_name(get_rel_namespace(rte->relid));
             objecttag = "Relation Name";
             break;

(and likewise for function schema names, a bit further down)?

            regards, tom lane

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index d276545..95ed602 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8480,15 +8480,15 @@ ANALYZE fprt2_p2;
 -- inner join three tables
 EXPLAIN (COSTS OFF)
 SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE
t1.a% 25 =0 ORDER BY 1,2,3; 
-                                                        QUERY PLAN
   

---------------------------------------------------------------------------------------------------------------------------
+                                             QUERY PLAN
+-----------------------------------------------------------------------------------------------------
  Sort
    Sort Key: t1.a, t3.c
    ->  Append
          ->  Foreign Scan
-               Relations: ((public.ftprt1_p1 t1) INNER JOIN (public.ftprt2_p1 t2)) INNER JOIN (public.ftprt1_p1 t3)
+               Relations: ((ftprt1_p1 t1) INNER JOIN (ftprt2_p1 t2)) INNER JOIN (ftprt1_p1 t3)
          ->  Foreign Scan
-               Relations: ((public.ftprt1_p2 t1_1) INNER JOIN (public.ftprt2_p2 t2_1)) INNER JOIN (public.ftprt1_p2
t3_1)
+               Relations: ((ftprt1_p2 t1_1) INNER JOIN (ftprt2_p2 t2_1)) INNER JOIN (ftprt1_p2 t3_1)
 (7 rows)

 SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE
t1.a% 25 =0 ORDER BY 1,2,3; 
@@ -8561,15 +8561,15 @@ SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1
 -- join with lateral reference
 EXPLAIN (COSTS OFF)
 SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE
t1.a%25= 0 ORDER BY 1,2; 
-                                     QUERY PLAN
--------------------------------------------------------------------------------------
+                              QUERY PLAN
+-----------------------------------------------------------------------
  Sort
    Sort Key: t1.a, t1.b
    ->  Append
          ->  Foreign Scan
-               Relations: (public.ftprt1_p1 t1) INNER JOIN (public.ftprt2_p1 t2)
+               Relations: (ftprt1_p1 t1) INNER JOIN (ftprt2_p1 t2)
          ->  Foreign Scan
-               Relations: (public.ftprt1_p2 t1_1) INNER JOIN (public.ftprt2_p2 t2_1)
+               Relations: (ftprt1_p2 t1_1) INNER JOIN (ftprt2_p2 t2_1)
 (7 rows)

 SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE
t1.a%25= 0 ORDER BY 1,2; 
@@ -8689,17 +8689,17 @@ SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 O
 SET enable_partitionwise_aggregate TO true;
 EXPLAIN (COSTS OFF)
 SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 ORDER BY 1;
-                         QUERY PLAN
--------------------------------------------------------------
+                      QUERY PLAN
+------------------------------------------------------
  Sort
    Sort Key: fpagg_tab_p1.a
    ->  Append
          ->  Foreign Scan
-               Relations: Aggregate on (public.fpagg_tab_p1)
+               Relations: Aggregate on (fpagg_tab_p1)
          ->  Foreign Scan
-               Relations: Aggregate on (public.fpagg_tab_p2)
+               Relations: Aggregate on (fpagg_tab_p2)
          ->  Foreign Scan
-               Relations: Aggregate on (public.fpagg_tab_p3)
+               Relations: Aggregate on (fpagg_tab_p3)
 (9 rows)

 SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 ORDER BY 1;
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 3eb4e40..bdc21b3 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2571,7 +2571,6 @@ postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
             {
                 int            rti = strtol(ptr, &ptr, 10);
                 RangeTblEntry *rte;
-                char       *namespace;
                 char       *relname;
                 char       *refname;

@@ -2580,11 +2579,19 @@ postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
                 rte = rt_fetch(rti, es->rtable);
                 Assert(rte->rtekind == RTE_RELATION);
                 /* This logic should agree with explain.c's ExplainTargetRel */
-                namespace = get_namespace_name(get_rel_namespace(rte->relid));
                 relname = get_rel_name(rte->relid);
-                appendStringInfo(relations, "%s.%s",
-                                 quote_identifier(namespace),
-                                 quote_identifier(relname));
+                if (es->verbose)
+                {
+                    char       *namespace;
+
+                    namespace = get_namespace_name(get_rel_namespace(rte->relid));
+                    appendStringInfo(relations, "%s.%s",
+                                     quote_identifier(namespace),
+                                     quote_identifier(relname));
+                }
+                else
+                    appendStringInfo(relations, "%s",
+                                     quote_identifier(relname));
                 refname = (char *) list_nth(es->rtable_names, rti - 1);
                 if (refname == NULL)
                     refname = rte->eref->aliasname;