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From Thorsten von Eicken <...@rightscale.com>
Subject trouble with deleted counter columns
Date Wed, 30 Nov 2011 07:36:56 GMT
Running a single 1.0.3 node and using counter columns I have a problem.
I have rows with ~200k counters. I deleted a number of such rows and now
I can't put counters back in, or really, I can't query what I put back in.

Example using the cli:
[default@rslog_production] get req_word_freq['20111124'];
Returned 0 results.
Elapsed time: 2089 msec(s).
[default@rslog_production] incr req_word_freq['20111124']['test'];
Value incremented.
[default@rslog_production] get req_word_freq['20111124'];
Returned 0 results.
Elapsed time: 2018 msec(s).

Note how long it's taking, presumably because it's going through 200K+
tombstones?

Here's the same using a fresh row key, note the timings:
[default@rslog_production] get req_word_freq['test'];
Returned 0 results.
Elapsed time: 1 msec(s).
[default@rslog_production] incr req_word_freq['test']['test'];
Value incremented.
[default@rslog_production] get req_word_freq['test'];
=> (counter=test, value=1)
Returned 1 results.
Elapsed time: 6 msec(s).

Incidentally, I then tried out deleting the column and I don't
understand why the value is 2 at the end:
[default@rslog_production] del req_word_freq['test'];
row removed.
[default@rslog_production] get req_word_freq['test'];
Returned 0 results.
Elapsed time: 1 msec(s).
[default@rslog_production] incr req_word_freq['test']['test'];
Value incremented.
[default@rslog_production] get req_word_freq['test'];
=> (counter=test, value=2)
Returned 1 results.
Elapsed time: 1 msec(s).

All this is on a single node system, running the cassandra-cli on the
system itself. The CF is as follows:
[default@rslog_production] describe req_word_freq;
    ColumnFamily: req_word_freq
      Key Validation Class: org.apache.cassandra.db.marshal.UTF8Type
      Default column value validator:
org.apache.cassandra.db.marshal.CounterColumnType
      Columns sorted by: org.apache.cassandra.db.marshal.UTF8Type
      Row cache size / save period in seconds / keys to save : 0.0/0/all
      Row Cache Provider:
org.apache.cassandra.cache.SerializingCacheProvider
      Key cache size / save period in seconds: 200000.0/14400
      GC grace seconds: 864000
      Compaction min/max thresholds: 4/32
      Read repair chance: 1.0
      Replicate on write: true
      Built indexes: []
      Compaction Strategy:
org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy

I must be missing something...
Thorsten


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