Re: WIP: Avoid creation of the free space map for small tables

On Mon, Jan 28, 2019 at 4:53 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> There are a few buildfarm failures due to this commit, see my email on
> pgsql-committers. If you have time, you can also once look into
> those.

I didn't see anything in common with the configs of the failed
members. None have a non-default BLCKSZ that I can see.

Looking at this typical example from woodlouse:

================== pgsql.build/src/test/regress/regression.diffs
==================
--- C:/buildfarm/buildenv/HEAD/pgsql.build/src/test/regress/expected/fsm.out
2019-01-28 04:43:09.031456700 +0100
+++ C:/buildfarm/buildenv/HEAD/pgsql.build/src/test/regress/results/fsm.out
2019-01-28 05:06:20.351100400 +0100
@@ -26,7 +26,7 @@
pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
heap_size | fsm_size
-----------+----------
- 24576 | 0
+ 32768 | 0
(1 row)

***It seems like the relation extended when the new records should
have gone into block 0.

-- Extend table with enough blocks to exceed the FSM threshold
@@ -56,7 +56,7 @@
SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
fsm_size
----------
- 16384
+ 24576
(1 row)

***And here it seems vacuum didn't truncate the FSM. I wonder if the
heap didn't get truncated either.

--
John Naylor https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services