|
|
QUESTION: We turned on autovacuums on 8.2 and we have a database which is read
only , it is basically a USPS database used only for address lookups
(only SELECTS, no updates/deletes/inserts).
This database has about 10gig data and yesterday autovacuum started
on this database and all of a sudden I see lot of archive logs generated
during this time, I guess it might have generated close to 3-4gig data
during this period.
It was doing only vacuum not vacuum analyze.
My question is why does it have to generate so many archive logs on
static tables ?
I am thinking these archive logs are mostly empty , the reason I am
saying that because I noticed that when I restore the db using PITR
backups for my reporting db these same logs are recovered in seconds
compared to the logs generated while vacuums are not running.
Is this a BUG ? or am I missing something here ?
ANSWER: Probably represents freezing of old tuples, which is a WAL-logged
operation as of 8.2. Is it likely that the data is 200M transactions
old?
|
|
|
|
