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: 2019-01-23T22:08:56Z
Lists: pgsql-hackers 
On Mon, Jan 21, 2019 at 6:32 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> Also, another case to think in this regard is the upgrade for standby
> servers, if you read below paragraph from the user manual [1], you
> will see what I am worried about?
>
> "What this does is to record the links created by pg_upgrade's link
> mode that connect files in the old and new clusters on the primary
> server. It then finds matching files in the standby's old cluster and
> creates links for them in the standby's new cluster. Files that were
> not linked on the primary are copied from the primary to the standby.
> (They are usually small.)"
>
> [1] - https://www.postgresql.org/docs/devel/pgupgrade.html

I am still not able to get the upgraded standby to go into recovery
without resorting to pg_basebackup, but in another attempt to
investigate your question I tried the following (data1 = old cluster,
data2 = new cluster):


mkdir -p data1 data2 standby

echo 'heap' > data1/foo
echo 'fsm' > data1/foo_fsm

# simulate streaming replication
rsync --archive data1 standby

# simulate pg_upgrade, skipping FSM
ln data1/foo -t data2/

rsync --archive --delete --hard-links --size-only --no-inc-recursive
data1 data2 standby

# result
ls standby/data1
ls standby/data2


The result is that foo_fsm is not copied to standby/data2, contrary to
what the docs above imply for other unlinked files. Can anyone shed
light on this?

-- 
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