cassandra copy data from one columnfamily to another columnfamily

Question

I am newbie to cassandra . I need to copy data from one columnFamily to another columnFamily in same keyspace in cassandra .Say for ex we have a A1 columnFamily in keyspace

Answer 1

Please be aware of a limit of max. 2 million rows when using the COPY command. See https://docs.datastax.com/en/cql/3.3/cql/cql_reference/cqlshCopy.html

Note: Only use COPY FROM to import datasets that have less than 2 million rows. To import large datasets, use the Cassandra bulk loader

Answer 2

cqlsh -k mykeyspace -e 'COPY fromTable(columnNames) TO STDOUT' | head -n -1 | cqlsh -k mykeyspace -e 'COPY toTable(columnNames) FROM STDIN'

Answer 3

Depending on the cassandra version you can use the copy cql command. To use that you need a cql client like the one that is distributted with cassandra.

First you have to copy the columnfamily A1 to a CSV file using:

COPY K1.A1 (column1, column2,...) TO 'temp.csv';

And after that copy the file to the new column family

COPY K1.A2 (column1, column2,...) FROM 'temp.csv';

Obviously you have to change the name of the columns to your names.

More information:

http://www.datastax.com/documentation/cassandra/1.2/index.html#cassandra/cql_reference/copy_r.html