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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Commit log changes in 0.7
Date Fri, 26 Feb 2010 20:39:53 GMT
Remember that the header is per-segment.  So I would just say that CF
modification forces a new segment creation.

We can support additions and deletions just by doing that, so that
should probably be the first milestone.  Renames are harder because
currently we map id -> name -> files on disk.  We'd need to change
that to id -> files on disk, id -> sequence of names and when they
were in effect for HH.  (Maybe this is the straw that breaks the HH
camel's back?)

-Jonathan

On Fri, Feb 26, 2010 at 11:22 AM, Gary Dusbabek <gdusbabek@gmail.com> wrote:
> The commit log currently has a header section whose size is constant,
> but is a function of the total number of defined column families.
> This isn't going to work with CASSANDRA-44 where CFs can be added or
> removed on the fly.  I see two options:
>
> 1.  hard code the size of the header to accommodate a maximum number
> of CFs.  I don't like this approach because it imposes a hard limit.
> 2.  move the header into its own file.  I don't like this because it
> adds complexity.
>
> Any better other ideas?
>
> Some background:  the data stored in the header indicates a) which CFs
> are 'dirty' and b) log replay offsets for each CF.
>

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