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

On Mon, Jan 21, 2019 at 6:32 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)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/
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