[Maposmatic-dev] Re: Growth of on-disk size of OSM database

[Frederik Ramm]

Hi,

Thomas Petazzoni wrote:
> We've done an initial import of this database in ~october 2009, and
> since then, we've used daily diffs to keep this database up to date. As
> of today, our PostgreSQL database takes 174 GB. However, during a
> discussion at SOTM, Frederik told us that the size of the world
> database resulting from a brand-new import would only be 120-130 GB.
> This seems to mean that using the daily diffs does not produce the same
> result as making a full import of the database. Is this true ?

Depends on what you define as "same result". If you make a full dump of 
your PostgreSQL tables and then re-import that, you will be somewhere at 
122 GB or so. You could also do a "vacuum full" to achieve the same 
result, or do a fresh import. But if you make a comparison of the files 
in your /var/lib/postgresql directory, these will not be the same as if 
you were to do a new import. The normal vacuuming that PostgreSQL does 
is insufficient to release some allocated space and later freed space in 
the data files, that's why your database is larger that it would have to 
be. Your select results will look the same.

Bye
Frederik