From: "Amit Kapila" <>
On Fri, Jul 4, 2014 at 7:29 PM, MauMau <> wrote:
Why does the connection processing emit WAL?

Probably, it did page-at-a-time vacuum during access to pg_database and
pg_authid for client authentication.  src/backend/access/heap/README.HOT

I agree with your analysis that it can happen during connection

Thank you.  I'm relieved the cause seems correct.

But the customer could not reproduce the problem when he performed the
same archive recovery from the same base backup again.  Why?  I guess the
autovacuum daemon vacuumed the system catalogs before he attempted to
connect to the database.

One way to confirm could be to perform the archive recovery by
disabling autovacuum.

Yeah, I thought of that too. Unfortunately, the customer deleted the the base backup for testing.

Another thing which I am wondering about is can't the same happen
even for Read Only transaction (incase someone does Select which
prunes the page).

I'm afraid about that, too.


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