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This project is derived from the work done at Riptano (now Datastax)
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There wouldn't have been anything if not for the original work done by Edward Capriolo. Look at the Apache Jira here
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Majority of the cleanup and upgrade to 1.2.x work was done by the wonderful guys (and our development partners) at Imaginea by Venkatesh Ragi
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Thanks to all the other contributors -
And of course countless others how have contributed to Cassandra, Hadoop and Hive and the Open Source community in general. THansk to each and everyone of you!
This handler provides hive support for cassandra.
check out the project from https://github.com/tuplejump/cash.git.
> git clone https://github.com/tuplejump/cash.git
Go to branch cas-support-cql
> git checkout cas-support-cql
Go to cassandra-handler folder run the maven package command.
> mvn package
This generates a hive-cassandra-x.x.x.jar file in target folder and all other project dependencies are downloaded to target/dependency.
Copy the target/hive-cassandra-x.x.x.jar to the hive lib directory
Copy target/dependency/cassandra-all-x.x.x.jar and target/dependency/cassandra-thrift-x.x.x.jar to hive lib directory.
Start hive
> bin/hive
Create a database in hive (or use an existing one)
To create a cql3 table in cassandra from hive, execute the following command
hive> CREATE EXTERNAL TABLE test.messages(message_id string, author string, body string)
STORED BY 'org.apache.hadoop.hive.cassandra.cql.CqlStorageHandler'
WITH SERDEPROPERTIES ("cql.primarykey" = "message_id, author", "comment"="check", "read_repair_chance" = "0.2",
"dclocal_read_repair_chance" = "0.14", "gc_grace_seconds" = "989898", "bloom_filter_fp_chance" = "0.2",
"compaction" = "{'class' : 'LeveledCompactionStrategy'}", "replicate_on_write" = "false", "caching" = "all")
where 'test' is the keyspace in cassandra. The above query also creates a column family in cassandra if does not exist.
Note: By default hive tries to use cassandra running on localhost at port 9160. To change these specify cassandra.host and cassandra.port in the SerDeProperties while creating a table. Hive connects to the specified cassandra instance for further queries to the table.
To create a keyspace that does not exist in cassandra execute the following query
hive> CREATE EXTERNAL TABLE test.messages(row_key string, col1 string, col2 string)
STORED BY 'org.apache.hadoop.hive.cassandra.cql.CqlStorageHandler' WITH SERDEPROPERTIES("cql.primarykey" = "row_key")
TBLPROPERTIES ("cassandra.ks.name" = "mycqlks", "cassandra.ks.stratOptions"="'DC':1, 'DC2':1",
"cassandra.ks.strategy"="NetworkTopologyStrategy");
Note: For brevity, only minimal SERDEPROPERTIES are given in the above query.
If 'test' keyspace does not exist in cassandra it will be created.
Inserting values into CQL3 table through hive:
hive> insert into table messages select * from tweets;
The values from tweets table are appended to messages table.
Note: With Cassandra INSERT OVERWRITE is same as INSERT INTO as Cassandra merges changes if keys are same.
Retrieving values from a CQL3 table using hive:
hive> select * from messages;
Note: If local mode execution is not enabled, hive compiler generates map-reduce jobs for most queries. These jobs are then submitted to the Map-Reduce cluster. The map-reduce jobs need hive-cassandra-handler, cassandra-all and cassandra-thrift jars. Point the HIVE_AUX_JARS_PATH environment variable to the location containing these jars to run those jobs successfully.
While CqlStorageHandler is used to create/access cql3 tables in cassandra, CassandraStorageHandler can be used to create/access thrift tables in cassandra.
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