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pythoncassandracomposite-keypycassapython-datetime

Can't insert into Cassandra column family using Pycassa with composite row keys (UTF8Type, DateType)

I've got a Cassandra column family (created using Pycassa) with the following schema:

ColumnFamily: tracker
  Key Validation Class: org.apache.cassandra.db.marshal.CompositeType(org.apache.cassandra.db.marshal.UTF8Type,org.apache.cassandra.db.marshal.DateType)
  Default column value validator: org.apache.cassandra.db.marshal.BytesType
  Cells sorted by: org.apache.cassandra.db.marshal.UTF8Type
  GC grace seconds: 864000
  Compaction min/max thresholds: 4/32
  Read repair chance: 0.1
  DC Local Read repair chance: 0.0
  Populate IO Cache on flush: false
  Replicate on write: true
  Caching: KEYS_ONLY
  Bloom Filter FP chance: default
  Built indexes: []
  Compaction Strategy: org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy
  Compression Options:
    sstable_compression: org.apache.cassandra.io.compress.SnappyCompressor

I'm trying to insert into it with the following line:

self.tracker_batcher.insert(tracker_key, dictionary_to_insert)

where tracker_key is:

('cd7449e8-8f0d-4730-9ee4-ef60edfdd409', datetime.datetime(2013, 8, 14, 16, 47, 55, 856000))

I'd expect this to work - I use datetypes in other tables as row keys and they work a treat. Additionally - it looks like I'm following the tutorial on the Pycassa site (http://pycassa.github.io/pycassa/assorted/composite_types.html).

For further information I'm using Pycassa version 1.9.0 and Cassandra 1.2.8

Thanks,

Matt

edit:

In a bizarre twist of events, the first error message I receive:

TypeError: A str or unicode value was expected, but datetime was received instead (2013-08-14 16:45:15.376000)

I tried modifying the query as such:

tracker_key = (str(dictionary_to_insert['session_id']), datetime.datetime.strftime(dictionary_to_insert['datestamp'], "%Y-%m-%d %H:%M:%S"))

i.e. changed the datetime to a string

and got the following error message:

    raise TypeError('DateType arguments must be a datetime or timestamp')
TypeError: DateType arguments must be a datetime or timestamp

Baffling.

Solution

  • So it looks like the problem wasn't actually with the row columns but with the values being inserted.

    I've specified that I'm going to be using UTF8Type as values but was trying to insert the same datetime that is used as part of the key as a value in the column family.

    Creating the tracker key and then converting the dictionary_to_insert value to a string fixes it :)