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From Peter Schuller <>
Subject Re: force gc?
Date Mon, 03 Sep 2012 05:17:27 GMT
> I think I described the problem wrong :) I don't want to do Java's memory
> GC. I want to do cassandra's GC - that is I want to "really" remove deleted
> rows from a column family and get my disc space back.

I think that was clear from your post. I don't see a problem with your
process. Setting gc grace to 0 and forcing compaction should indeed
return you to the smallest possible on-disk size.

Did you really not see a *decrease*, or are you just comparing the
final size with that of PostgreSQL? Keep in mind that in many cases
(especially if not using compression) the Cassandra on-disk format is
not as compact as PostgreSQL. For example column names are duplicated
in each row, and the row key is duplicated twice (once in index, once
in data).

/ Peter Schuller (@scode,

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