Hot Standby startup with overflowed snapshots - Mailing list pgsql-hackers

From Simon Riggs
Subject Hot Standby startup with overflowed snapshots
Date
Msg-id CA+U5nMJ3-kAFtRZo5g7gRjp0iA4BwdavbbH9_UQsekeqT-2m1A@mail.gmail.com
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Responses Re: Hot Standby startup with overflowed snapshots  (Chris Redekop <chris@replicon.com>)
List pgsql-hackers
Chris Redekop's recent report of slow startup for Hot Standby has made
me revisit the code there.

Although there isn't a bug, there is a missed opportunity for starting
up faster which could be the source of Chris' annoyance.

The following patch allows a faster startup in some circumstances.

The patch also alters the log levels for messages and gives a single
simple message for this situation. The log will now say

  LOG:  recovery snapshot waiting for non-overflowed snapshot or until
oldest active xid on standby is at least %u (now %u)
  ...multiple times until snapshot non-overflowed or xid reached...

whereas before the first LOG message shown was

  LOG:  consistent state delayed because recovery snapshot incomplete
  and only later, at DEBUG2 do you see
  LOG:  recovery snapshot waiting for %u oldest active xid on standby is %u
  ...multiple times until xid reached...

Comments please.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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