Horton

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

John Naylor <john.naylor@2ndquadrant.com>

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From: John Naylor <john.naylor@2ndquadrant.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Mithun Cy <mithun.cy@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-28T04:33:12Z
Lists: pgsql-hackers 
On Mon, Jan 28, 2019 at 4:53 AM Amit Kapila <amit.kapila16@gmail.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

Commits

  1. Improve code comments in b0eaa4c51b.

  2. During pg_upgrade, conditionally skip transfer of FSMs.

  3. Add more tests for FSM.

  4. Doc: Update the documentation for FSM behavior for small tables.

  5. Make FSM test portable.

  6. Avoid creation of the free space map for small heap relations, take 2.

  7. Move page initialization from RelationAddExtraBlocks() to use, take 2.

  8. Avoid creation of the free space map for small heap relations.

  9. In bootstrap mode, don't allow the creation of files if they don't already