Using Cassandra and CQL3, how do you insert an entire wide row in a single request?

问题

I want to insert a single row with 50,000 columns into Cassandra 1.2.8. Before inserting, I have all the data for the entire row ready to go (in memory):

+---------+------+------+------+------+-------+
|         | 0    | 1    | 2    | ...  | 49999 |
| row_id  +------+------+------+------+-------+
|         | text | text | text | ...  | text  |
+---------+------+------+------|------+-------+

The column names are integers, allowing slicing for pagination. The column values are a value at that particular index.

CQL3 table definition:

create table results (
    row_id text,
    index int,
    value text,
    primary key (row_id, index)
) 
with compact storage;

As I already have the row_id and all 50,000 name/value pairs in memory, I just want to insert a single row into Cassandra in a single request/operation so it is as fast as possible.

The only thing I can seem to find is to do execute the following 50,000 times:

INSERT INTO results (row_id, index, value) values (my_row_id, ?, ?);

the first ? is is an index counter (i) and the second ? is the text value to store at location i.

This takes a lot of time. Even when we put the above INSERTs into a batch, it takes a lot of time.

We have all the data we need (the complete row) in its entirety, I would assume it to be very easy to just say "here, Cassandra, store this data as a single row in one request", for example:

//EXAMPLE-BUT-INVALID CQL3 SYNTAX:
insert into results (row_id, (index,value)) values 
    ((0,text0), (1,text1), (2,text2), ..., (N,textN));

This example isn't possible via current CQL3 syntax, but I hope it illustrates the desired effect: everything would be inserted as a single query.

Is it possible to do this in CQL3 and the DataStax Java Driver? If not, I suppose I'll be forced to use Hector or the Astyanax driver and the Thrift batch_insert operation instead?

回答1:

Multiple INSERTs / UPDATEs can be done using batch_mutate method in Thrift APIs, by making use of mutation multi-maps.

Map<byte[], Map<String, List<Mutation>>> mutationMap = new HashMap<byte[], Map<String, List<Mutation>>>();

List<Mutation> mutationList = new ArrayList<Mutation>();

mutationList.add(mutation);
Map<String, List<Mutation>> m = new HashMap<String, List<Mutation>>();

m.put(columnFamily, mutationList);

mutationMap.put(key, m);
client.batch_mutate(mutationMap, ConsistencyLevel.ALL);

回答2:

Edit: only 4 days after I posted this question regarding Cassandra 1.2.9, Cassandra 2.0 final was released. 2.0 supports batch prepared statements, which should be much faster than the non-batched CQL3 that was required to be used for C* < 2.0. We have not yet tested this to be sure.

When this question was posted 4 days ago on 30 August 2013, it was not possible in CQL3 for C* versions less than 2.0. It was only possible via a Thrift client, e.g. Astyanax's MutationBatch.

Per Alex's suggestion, I created CASSANDRA-5959 as a feature request, but it was marked as a duplicate to CASSANDRA-4693, which supposedly solved the issue for C* 2.0.

回答3:

CQL3 INSERT statement doesn't support multiple value tuples. But I think this could make an interesting addition to CQL so please submit a feature request.
The DataStax Java driver is based on CQL so there's anything it can do if the statement is not supported.
For the time being if you need this your best option would be to use a Thrift-based library (nb: I'm not very familiar with Thrift-based API to confirm this insert would be possible, but I think it should)

回答4:

Use Batch statement in CQL3 if you want to do multiple insert.

With C* 2.0, it'll be even easier and faster since they'll enable prepared statement in batch

来源：https://stackoverflow.com/questions/18522191/using-cassandra-and-cql3-how-do-you-insert-an-entire-wide-row-in-a-single-reque

标签

cassandra

cql3

datastax-java-driver