Re: Why is DEFAULT_FDW_TUPLE_COST so insanely low?

On Thu, Nov 2, 2023 at 3:19 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> I'm not yet seeing any failures in the buildfarm, so don't really want
> to push a fix for this one if there are going to be a few more
> unstable ones to fix. I may just hold off a while to see.

It seems that the test is still not stable on 32-bit machines even after
4b14e18714. I see the following plan diff on cfbot [1].

--- /tmp/cirrus-ci-build/contrib/postgres_fdw/expected/postgres_fdw.out
2023-11-02 11:35:12.016196978 +0000
+++
/tmp/cirrus-ci-build/build-32/testrun/postgres_fdw/regress/results/postgres_fdw.out
2023-11-02 11:42:09.092242808 +0000
@@ -4022,24 +4022,21 @@
-- subquery using stable function (can't be sent to remote)
PREPARE st2(int) AS SELECT * FROM ft1 t1 WHERE t1.c1 < $2 AND t1.c3 IN
(SELECT c3 FROM ft2 t2 WHERE c1 > $1 AND date(c4) = '1970-01-17'::date)
ORDER BY c1;
EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st2(10, 20);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------
+ Nested Loop Semi Join
Output: t1.c1, t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7, t1.c8
- Sort Key: t1.c1
- -> Nested Loop Semi Join
+ Join Filter: (t2.c3 = t1.c3)
+ -> Foreign Scan on public.ft1 t1
Output: t1.c1, t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7, t1.c8
- Join Filter: (t2.c3 = t1.c3)
- -> Foreign Scan on public.ft1 t1
- Output: t1.c1, t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7,
t1.c8
- Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM
"S 1"."T 1" WHERE (("C 1" < 20))
- -> Materialize
+ Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S
1"."T 1" WHERE (("C 1" < 20)) ORDER BY "C 1" ASC NULLS LAST
+ -> Materialize
+ Output: t2.c3
+ -> Foreign Scan on public.ft2 t2
Output: t2.c3
- -> Foreign Scan on public.ft2 t2
- Output: t2.c3
- Filter: (date(t2.c4) = '01-17-1970'::date)
- Remote SQL: SELECT c3, c4 FROM "S 1"."T 1" WHERE (("C
1" > 10))
-(15 rows)
+ Filter: (date(t2.c4) = '01-17-1970'::date)
+ Remote SQL: SELECT c3, c4 FROM "S 1"."T 1" WHERE (("C 1" >
10))
+(12 rows)

[1]
https://api.cirrus-ci.com/v1/artifact/task/5727898984775680/testrun/build-32/testrun/postgres_fdw/regress/regression.diffs

Thanks
Richard