Re: pg_database_size differs from df -s

Frank Lanitz <frank(at)frank(dot)uvena(dot)de> writes:
> I've got an issue I'm not sure I might have a misunderstanding. When
> calling

> select sum(pg_database_size(datid)) as total_size from pg_stat_database

> the result is much bigger than running a df -s over the postgres folder
> - Its about factor 5 to 10 depending on database.

Did you mean "du -s"?

> My understanding was, pg_database_size is the database size on disc. Am
> I misunderstanding the docu here?

For me, pg_database_size gives numbers that match up fairly well with
what "du" says. I would not expect an exact match, since du probably
knows about filesystem overhead (such as metadata) whereas
pg_database_size does not. Something's fishy if it's off by any large
factor, though. Perhaps you have some tables in a nondefault
tablespace, where du isn't seeing them?

regards, tom lane