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From "Sylvain Lebresne (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-1546) (Yet another) approach to counting
Date Mon, 04 Oct 2010 12:33:46 GMT


Sylvain Lebresne commented on CASSANDRA-1546:

I'm a little wary of having "bad" state on disk, because it introduces additional variables
that have to be reasoned about.
As of 2 months ago, AES doesn't perform a read-only major compaction like it did in 0.6. It
streams across the relevant subsections of each SST on disk to the target node, which is concatenated
into a new SST. So, if:
1) A streams an AES repair SST to B,
2) that streamed SST is never transformed (e.g. via compaction), then
3) B streams an AES repair SST back to A.

It will send the untransformed columns from A, back to A. When I have time, I'll re-read the
compaction code to make sure this hasn't changed.

I'll admit that if AES doesn't perform any deserialization, I have missed that. I'll re-read
the AES code too.
If so, then yes, it's broken. And in any case, I don't disagree with you that it may well
not be a good idea to
rely on such variable. I'm not against forcing deserialization after streaming to rebuild
the sstable, at least 
for counter CFs. Anyway, the AES code should also be updated since right now the building
of the merkle tree is
broken (the has of counter supercolumns will be different on all node right now).

> (Yet another) approach to counting
> ----------------------------------
>                 Key: CASSANDRA-1546
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 0.7.0
>         Attachments: 0001-Remove-IClock-from-internals.patch, 0001-v2-Remove-IClock-from-internals.patch,
0002-Counters.patch, 0002-v2-Counters.patch, 0003-Generated-thrift-files-changes.patch, 0003-v2-Thrift-changes.patch
> This could be described as a mix between CASSANDRA-1072 without clocks and CASSANDRA-1421.
> More details in the comment below.

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