This is a bit of a wild guess but Windows and encoding and 0.7.5 sounds like
https://issues.apache.org/jira/browse/CASSANDRA-2367 On May 3, 2011, at 5:15 PM, Henrik Schröder wrote: > Hey everyone, > > We did some tests before upgrading our Cassandra cluster from 0.6 to 0.7, > just to make sure that the change in how keys are encoded wouldn't cause us > any dataloss. Unfortunately it seems that rows stored under a unicode key > couldn't be retrieved after the upgrade. We're running everything on Windows, > and we're using the generated thrift client in C# to access it. > > I managed to make a minimal test to reproduce the error consistently: > > First, I started up Cassandra 0.6.13 with an empty data directory, and a > really simple config with a single keyspace with a single bytestype > columnfamily. > I wrote two rows, each with a single column with a simple column name and a > 1-byte value of "1". The first row had a key using only ascii chars ('foo'), > and the second row had a key using unicode chars ('ドメインウ'). > > Using multi_get, and both those keys, I got both columns back, as expected. > Using multi_get_slice and both those keys, I got both columns back, as > expected. > I also did a get_range_slices to get all rows in the columnfamily, and I got > both columns back, as expected. > > So far so good. Then I drain and shut down Cassandra 0.6.13, and start up > Cassandra 0.7.5, pointing to the same data directory, with a config > containing the same keyspace, and I run the schematool import command. > > I then start up my test program that uses the new thrift api, and run some > commands. > > Using multi_get_slice, and those two keys encoded as UTF8 byte-arrays, I only > get back one column, the one under the key 'foo'. The other row I simply > can't retrieve. > > However, when I use get_range_slices to get all rows, I get back two rows, > with the correct column values, and the byte-array keys are identical to my > encoded keys, and when I decode the byte-arrays as UTF8 drings, I get back my > two original keys. This means that both my rows are still there, the keys as > output by Cassandra are identical to the original string keys I used when I > created the rows in 0.6.13, but it's just impossible to retrieve the second > row. > > To continue the test, I inserted a row with the key 'ドメインウ' encoded as UTF-8 > again, and gave it a similar column as the original, but with a 1-byte value > of "2". > > Now, when I use multi_get_slice with my two encoded keys, I get back two > rows, the 'foo' row has the old value as expected, and the other row has the > new value as expected. > > However, when I use get_range_slices to get all rows, I get back *three* > rows, two of which have the *exact same* byte-array key, one has the old > column, one has the new column. > > > How is this possible? How can there be two different rows with the exact same > key? I'm guessing that it's related to the encoding of string keys in 0.6, > and that the internal representation is off somehow. I checked the generated > thrift client for 0.6, and it UTF8-encodes all keys before sending them to > the server, so it should be UTF8 all the way, but apparently it isn't. > > Has anyone else experienced the same problem? Is it a platform-specific > problem? Is there a way to avoid this and upgrade from 0.6 to 0.7 and not > lose any rows? I would also really like to know which byte-array I should > send in to get back that second row, there's gotta be some key that can be > used to get it, the row is still there after all. > > > /Henrik Schröder
