On 12/14/2011 11:52 AM, Carlos Mennens wrote:
I'm wanted to find out why is it recommended or even an option to lock tables during a backup of a database? I've never experimented with database backups so I'm only guessing it locks / freezes the data so no changes can be made while the backup is in process, correct? Just curious and wasn't able to find an answer online. My next question is more complex but more of a recommendations. I'm looking to see how do you guys backup your databases? Do you simply cron 'pg_dump' command line or do you have a script that gets called in cron using 'pg_dump' / 'pg_dumpall'? Just looking for ideas / recommendations for a simple / quick way to back up 5 small databases on my server.
I assume that is coming from a mysql world, where yes, locking is a good option.
PG does not need it. Read up on MVCC. Your backup will "select * from table" and read it just fine. Other transactions can update/delete from the same table, but because of the magic of MVCC, the backup wont see em, and neither will be blocked.
Meaning, your reads and writes dont block each other. Meaning, your app wont freeze while the backup runs.
Yep, you simply cron a pg_dump. (dumpall if you want users/roles and all databases). No locking needed.
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