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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Created: (CASSANDRA-1417) add cache save/load
Date Sat, 21 Aug 2010 12:35:19 GMT
add cache save/load
-------------------

                 Key: CASSANDRA-1417
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1417
             Project: Cassandra
          Issue Type: New Feature
          Components: Core
            Reporter: Jonathan Ellis
             Fix For: 0.6.6, 0.7 beta 2


Since mixing 0.7 nodes with 0.6 is looking increasingly unlikely to be supported because of
the deep changes to Thrift, we should allow saving out the 0.6 cache and loading it on startup
so that we don't inflict the pain of an entire cluster of cold cache on upgraders.

The cache format should just be a list of row keys.  Loading it is as simple as calling getColumnFamily
(with a zero-column predicate) on each row, for row cache.

Key cache is more complicated, but only a little.  First is that you have to de-duplicate
the row keys from multiple sstables.  (Saving which sstable version it's associated with is
less useful, since that will be obsoleted by compaction.)  Second is that we don't need to
actually read any row data, we just need to go through the index locator part of the read
path (getPosition).

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