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

From: Frederik Ramm
Subject: [Maposmatic-dev] Re: Growth of on-disk size of OSM database
Date: Wed, 14 Jul 2010 12:26:57 +0200
User-agent: Thunderbird (X11/20100317)


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.


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