Horton

Re: Sync Replication with transaction-controlled durability

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: pgsql-hackers@postgresql.org
Date: 2010-09-15T08:54:32Z
Lists: pgsql-hackers 
On 14/09/10 20:48, Simon Riggs wrote:
> When each new messages arrives from master the WALreceiver will write
> the new data to the WAL file, wake the WALwriter and then reply. Each
> new message from master receives a reply. If no further WAL data has
> been received the WALreceiver waits on the latch. If the WALReceiver is
> woken by WALWriter or Startup then it will reply to master with a
> message, even if no new WAL has been received.

Wrt. the earlier discussion about when the standby sends the 
acknowledgment, this is the key paragraph. So you *are* sending multiple 
acknowledgments per transaction, but there is some smarts to combine 
them when there's a lot of traffic. Fair enough.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com