Cassandra: Cannot parse <col_Name> as hex bytes: MarshallException - exception

Question

I was trying my first 'Helloworld' application in Cassandra. Whenever I try to add any data to my keyspace column family I get this error:
[default#MyKeyspace] set User['ehewitt'] ['fname']='Eben';
org.apache.cassandra.serializers.MarshalException: cannot parse 'fname' as hex bytes
This is despite the fact that I have executed
[default#MyKeyspace] assume Users keys as utf8;
So the above command does not seem to have any effect at all. How do I solve this issue?

Answer 1

Cassandra is assuming the columns as bytes.
Check with
help assume;
assume User keys as ascii;
assume User comparator as ascii;
assume User validator as ascii;
assume User sub_comparator as ascii;
set User['ehewitt']['fname']='Eben';
Value inserted.
Elapsed time: 216 msec(s).

Answer 2

I had similar problem, but the cli told me that the value is what cannot be parsed.
set game_outcome['1']['userId']='123asdasd';
cannot parse '123asdasd' as hex bytes
so I tried to use utf8 function like this :
set game_outcome['1']['userId']=utf8('123asdasd');
cannot parse '123asdasd' as hex bytes
Try
set User['ehewitt'] [utf8('fname')]='Eben'
I tried to use set some assumption like this
assume validator keys as utf8;
validator not found in current keyspace.
But as you can see it did not work as well !
I hope this answer helps.

Answer 3

Starting the CLI
You can start the CLI using the bin/cassandra-cli script in your Cassandra installation (bin\cassandra-cli.bat on windows). If you are evaluating a local cassandra node then be sure that it has been correctly configured and successfully started before starting the CLI.
If successful you will see output similar to this:
Welcome to cassandra CLI.
Type 'help;' or '?' for help. Type 'quit;' or 'exit;' to quit.
You must then specify a system to connect to:
connect localhost/9160;
Creating a Keyspace
We first create a keyspace to run our examples in.
create keyspace Twissandra;
Selecting the keyspace to user
We must then select our example keyspace as our new context before we can run any queries.
use Twissandra;
To Create A Column
We can then create a column to play with.
create column family User with comparator = UTF8Type;
For the later examples to work you must also update the schema using the following command. This will set the return type for the first and last name to make them human readable. It will also add and index for the age field so that you filter your gets using the Users name field.
update column family User with
column_metadata =
[
{column_name: first, validation_class: UTF8Type},
{column_name: last, validation_class: UTF8Type},
{column_name: age, validation_class: UTF8Type, index_type: KEYS}
];
To Add Data
To add data we want to into our new column we must first specify our default key type otherwise we would have to specify it for each key using the format [utf8('keyname')] this is probably advisable if you have mixed key types but makes simple cases harder to read.
So we run the command below, which will last the length of you cli session. On quitting and restarting we must run it again.
assume User keys as utf8;
and then we add our data.
set User['jsmith']['first'] = 'John';
set User['jsmith']['last'] = 'Smith';
set User['jsmith']['age'] = '38';
If you get the error like this cannot parse 'John' as hex bytes, then it likely you either haven't set your default key type or you haven't updated your schema as in the create column example.
To Update Data
If we need to update a value we simply set it again.
set User['jsmith']['first'] = 'Jack';
To Get Data
Now let's read back the jsmith row to see what it contains:
get User['jsmith'];
The get command uses API#get_slice
To Query Data
get User where age = '12';