On 2012-Jan-21, at 6:39 PM, Scott Marlowe wrote:
> On Sat, Jan 21, 2012 at 1:37 AM, Dan Charrois <dan001@xxxxxxx> wrote:
>> Hi everyone. I'm currently in the situation of administering a rather large PostgreSQL database which for some reason seems to be even much larger than it should be.
>>
>> I'm currently running version 8.4.5 - not the latest and greatest, I know - but this is a live database that would problematic to take down to upgrade unless all else fails - especially considering its size if it does need to be rebuilt somehow.
>>
>> Anyway, I'm no stranger to SQL, but new to PostgreSQL - all my SQL administration in the past has been with MySQL. So I'm somewhat bumbling my way through administrative commands trying to solve this - please bear with me.
>>
>> The size of the tables reported by \dt+ add up to around 120 GB. The size of the indexes reported with \di+ adds up to around 15 GB. This is pretty consistent with what I would expect the data to require.
>>
>> The problem is, the disk usage of the pgsql directory where the data is kept (as reported by 'du') comes to 647 GB - significantly more than it should. select pg_database_size('mydatabase') confirms this, returning 690830939920.
>>
>> Vacuuming the tables (full and otherwise) hasn't helped, but then considering how the database is used, I didn't really expect it to. It's strictly a read-only database, with the exception of once a month when it is refreshed by loading new data into newly created tables, and once that is done, vacuum analyzing the new tables, dropping the old tables, then renaming the new ones to have the name of the old ones. Vacuums never claim to recover any space, and the disk usage stays the same.
>>
>> So how do I find out what's eating up all this extra space?
>
> Real quick, if you run pg_database_size(name) for each db, including
> template1 and postgres, what do you get back?
Thanks for your reply, Scott.
My database: 697490323216
postgres: 5537796
template0: 5537796
template1: 5537796
pg_database_size(mydatabase) did return a value consistent with disk usage. But that value didn't jive with what I expected from summing up the sizes I got from \dt+
It looks like a large TOAST table, not reported by \dt+ was the biggest culprit, but I thought it was orphaned. Due to some help by Adrian Klaver, it looks like I was mistaken - it was in fact used by one of my tables. So it looks like there wasn't really a problem at all - other than my data still taking up a lot more physical storage than I thought it did. I don't think there's much I can do about it, but that's much better than assuming it was related to a problem that needed fixing.
Thanks again!
Dan
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