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Björn Hegerfors commented on CASSANDRA-9211:
--------------------------------------------
I have started with a first pass at this system table in this branch:
https://github.com/Bj0rnen/cassandra/tree/Bj0rnen/SSTableMetadataHistory. I
haven't tried yet, but figuring out when to do insertions to this table could
be difficult. I think it should be when the SSTable first gets loaded by
Cassandra, but if you restart Cassandra, I guess all SSTables will be loaded
again, and then it seems unnecessary to insert them another time. But it
wouldn't be too bad. If anyone can point me to a good place for writing to this
table, that would be helpful! I'm not only interested in SSTables that come
from compaction, since I want to know metadata about the ones that are the
input to a compaction operation, not just the output.
> Keep history of SSTable metadata
> --------------------------------
>
> Key: CASSANDRA-9211
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9211
> Project: Cassandra
> Issue Type: Wish
> Reporter: Björn Hegerfors
>
> Similar to the request in CASSANDRA-8078, I'm interested in SSTables'
> lineage. Specifically, I want to visualize the behaviors of compaction
> strategies based on real data. For example, for STCS I might want to generate
> something like this image:
> http://www.datastax.com/wp-content/uploads/2011/10/size-tiered-1.png. For LCS
> and DTCS, other properties than size are interesting.
> As Marcus responded in CASSANDRA-8078, there is already tracking of ancestors
> in the SSTable metadata. But as far as I know, the metadata gets garbage
> collected along with the SSTable itself. So what I propose is to persist
> metadata in a system table. Maybe some, maybe all metadata. Like the
> compaction_history table, this should have a default TTL of something like
> one week or just one day. But users can freely modify/remove the TTL.
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