On 2/2/15 7:36 PM, Jim Nasby wrote:
Currently the fact that it needs to go back to old tables and FTS them
every 2B transactions (or rely on autovacuum for this) and you can't do
anything about it (like permanently freeze the tables) seems like a big
scalability issue. Does it not?
Unfortunately it's not terribly easy to fix this. The problem is if we
try to play games here, we must have a 100% reliable method for changing
relfrozenxid as soon as someone inserts a new tuple in the relation. It
might be possible to tie this into the visibility map, but no one has
looked at this yet.
Perhaps you'd be willing to investigate this, or sponsor the work?
Oh, there is another possibility that's been discussed: read-only
tables. If we had the ability to mark a table read-only, then a VACUUM
FREEZE on such a table would be able to set that table's relfrozenxid to
FrozenTransactionId and prevent any further attempts at vacuuming. This
might be easier than trying to do something automatic.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com
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