Hi! Jeff, this depends on the DB engine you are using.
On Postgresql, you have two sets of files. The base files, which contains the "stable" data, and the write-ahead logs (WALs). Every time you do an operation, whatever that is (including delete), the operation is written to the WALs. Data in WALs is never overwritten, only appended.
From time to time (namely, when a WAL file is full - usually 16 MB, and when no active transaction is using that file) the data on the WAL files is copied back to the base files, and the WALs are discarded.
Even so, this might not release unused space. To do that, you have to run VACUUM queries. Note that running VACUUM on a table (or the entire DB) is a very heavy process, specially for the disks, so it will kill your DB performance while it's being done. Anyway, you don't really need to, because PostgreSQL will be able to use the unused space in a smart way, and it automatically vacuums some tables from time to time.
Note also that each DB has it's own procedure for making a correct backup (ie, a backup you are 100% sure it's consistent and will work if recovery is needed). Here's what you should do for PostgreSQL: http://www.postgresql.org/docs/8.1/interactive/backup.html . Note that, on most DBs (if not all), simply copying the DB files for another drive is NOT a safe way to backup, your backup will most probably be corrupt. You have to make the backups in accordance with the DB engine itself.
Yours Miguel Arroz On 2009/03/17, at 09:02, Jeff Schmitz wrote:
This may be a dumb question, but why after deleting a bunch of EOs is my database backup larger than before? Looking at the data in the database, the data corresponding to the EOs does seem to be gone now.Jeff _______________________________________________ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list ([email protected]) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/arroz%40guiamac.com This email sent to [email protected]
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