Cassandra Data Dictionary CSQL QUERIES AND SCRIPTS

Cassandra Data Dictionary CSQL QUERIES AND SCRIPTS

1)

How to List All Tables in Cassandra ?

cqlsh>use <key_space>;

The keyspace is another term for the name of the database that you are using. For example, I can type in: use db;

1	cqlsh:db> describe tables;

There you go! The command lists all tables within that key space.

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2) How to run cql files (.cql) from within cqlsh?

Assuming that the path of the file with the CQL commands is /mydir/myfile.cql, there are two ways:

If you are not logged in to cqlsh:

cqlsh -u 'my_username' -p 'my_password' -f /mydir/myfile.cql

If you are logged in to cqlsh:

SOURCE '/mydir/myfile.cql'

Notice the single quotation marks. The shorthand notation for $HOME (for example, '~/mydir/myfile.cql') is also supported.

Both ways also work with relative paths (to the current directory).

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3) Keyspace, table, and column information ?

An alternative to the cqlsh describe_* functions or using DevCenter to discover keyspace, table, and column information is querying system.schema_* table directly.

Procedure

• Query the defined keyspaces using the SELECT statement.

  cqlsh> SELECT * FROM system.schema_keyspaces;

  
  

  
• Query schema_columnfamilies about a particular table.

  cqlsh> SELECT * FROM system.schema_columnfamilies WHERE keyspace_name = 'cycling' AND columnfamily_name = 'cyclist_name';

  
• Query schema_columns about the columns in a table.

  cqlsh> SELECT * FROM system.schema_columns WHERE keyspace_name = 'cycling' AND columnfamily_name = 'cyclist_name';

  

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4) How to find out dropped columns ?

cqlsh:system_schema> select * from system_schema.dropped_columns; keyspace_name | table_name | column_name | dropped_time | type ---------------+------------+-------------+--------------------------+------ dev | foo | baz | 2016-02-07 05:26:10+0000 | text

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5) How to  get column names of a columnfamily?

SELECT column_name FROM system.schema_columnfamilies 
  WHERE keyspace_name = 'testks' AND columnfamily_name = 'testcf';

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