On Mon, 18 Apr 2005, Rob Butler wrote:
I'd say it's very not cool :) It's not we all expected from PITR. I recall now Simon mentioned about that and have it in his TODO. Other thing I don't understand what's the problem to generate WAL file by demand ? Probably, TODO should says about this.
This would definetly be a good feature to have. What I would prefer is:
1) have the pitr stop command write out and close the WAL that it is currently using.
2) have another stored proc which can be invoked at any time that will write out and close the WAL that is currently in use when that command is executed.
3) have a feature in postgres that will automatically write out and close the WAL if the server hasn't had any activity in XX minutes, or hasn't closed a WAL file in XX minutes.
The reason for this is "the Friday night" scenario.
This is exactly what I'm worry about ! Very typical scenario. I hope PITR improvement could be done in 8.0.X development cycle.
Let's say you have your WAL's FTP'd to a remote server off-site. Friday at 4:50 PM Postgres starts a new WAL, and everyone goes home for the weekend at 5pm. No activity occurs on the database all weekend long, so the new WAL never fills and is never closed. If something should happen during the weekend, and the disks are ruined on the PG DB server, the last WAL is never sent to the remote off-site server. The last transactions of the day are lost, even though they could have taken place days ago. With feature 3, you can guarantee that the oldest WAL is XX minutes old, so at least you have all the transactions within the last XX minutes.
Of course feature #3 also needs to have some smarts to it, so it doesn't create a bunch of completely empty WAL's everytime the timer runs out. It should only write and close the WAL if there is actually some new data in it.
Later Rob
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