Rural Hunter <ruralhunter@gmail.com> wrote:
> 2011/8/29 23:18, Kevin Grittner:
>> I also recommend a VACUUM FREEZE ANALYZE on the database unless
>> most of these rows will be deleted or updated before you run a
>> billion database transactions. Otherwise you will get a painful
>> "anti-wraparound" autovacuum on everything, probably at a time
>> of heavy usage.
> hmm....I will try to turn autovacuum off though I didn't see any
> resource intension caused by it.
Well, turning off autovacuum during a bulk load is probably a net
gain if it's insert-only (i.e., no need to query just-loaded data to
decide what to do with new rows); but that's not what I was getting
at. Bulk loading 200 GB of data which is not going to be deleted or
updated heavily is setting a performance time bomb without a VACUUM
FREEZE. At some point, perhaps months later, it will be necessary
to freeze the tuples to prevent data loss, and since this occurs
based on a threshold of how many transaction IDs have been consumed,
it is most likely to happen at peak OLTP loads, when it will be the
biggest problem. A VACUUM FREEZE (and you might as well throw in
ANALYZE while you're at it) will take care of that up front. As a
side benefit it will keep SELECT statements from generating heavy
*write* loads on the first access to tuples, and will perform other
maintenance which will improve database performance.
I just count the time for VACUUM FREEZE ANALYZE as part of the bulk
load time required before letting in users.
>> Network latency?
> No, I do the import locally on the db server so the network
> letency can be excluded.
Hmm... I don't remember the details, but there was a problem at
some point where Linux pipe connections could introduce significant
latency, and you could get much better performance on a TCP
connection through localhost. It might be worth a try. (Maybe
someone else will remember the details.)
-Kevin