On Jun 5, 2015, at 8:42 AM, Igor Neyman <ineyman@perceptron.com> wrote:
>
> The problem I see with “checksum utility” is that for it to work both compared servers should be “static”: not
transactionswhile it does its job.
Indeed, and that was brought up before and OP seems to be ignoring it. What magic does MySQL (supposedly) use to
comparedatabases without interfering with updates?
One could imagine a built-in feature in PG which depends on using MVCC and having both sides look at the same snapshot.
(Whichwould require repeatable reads.)
But for an external utility, that's quite a bit harder. One suggestion which would involve minimal interruption to
processing:if you have a snapshottable file system, shut down master, take snapshot, shut down replica, bring master
backup, snapshot replica, bring it back up. You *still* have the issue of making sure that at the moment you take
masterdown all changes have been streamed to replica, and the (easier) issue of making sure replica has applied them
beforetaking its snapshot... But if you can manage to pull that off, then you can checksum & compare as much as you
want,*IF* you can actually pull that off correctly ;-)
--
Scott Ribe
scott_ribe@elevated-dev.com
http://www.elevated-dev.com/
https://www.linkedin.com/in/scottribe/
(303) 722-0567 voice
