Cassandra Documentation


Secondary Indexes

CQL supports creating secondary indexes on tables, allowing queries on the table to use those indexes. A secondary index is identified by a name defined by:

index_name::= re('[a-zA-Z_0-9]+')


Creating a secondary index on a table uses the CREATE INDEX statement:

create_index_statement::= CREATE [ CUSTOM ] INDEX [ IF NOT EXISTS ] [ index_name ]
	ON table_name '(' index_identifier ')'
	[ USING string [ WITH OPTIONS = map_literal ] ]
index_identifier::= column_name
	| ( KEYS | VALUES | ENTRIES | FULL ) '(' column_name ')'

For instance:

CREATE INDEX userIndex ON NerdMovies (user);
CREATE INDEX ON Mutants (abilityId);
CREATE INDEX ON users (keys(favs));
   USING '';
   USING ''
   WITH OPTIONS = {'storage': '/mnt/ssd/indexes/'};

The CREATE INDEX statement is used to create a new (automatic) secondary index for a given (existing) column in a given table. A name for the index itself can be specified before the ON keyword, if desired. If data already exists for the column, it will be indexed asynchronously. After the index is created, new data for the column is indexed automatically at insertion time.

Attempting to create an already existing index will return an error unless the IF NOT EXISTS option is used. If it is used, the statement will be a no-op if the index already exists.

Indexes on Map Keys

When creating an index on a maps <maps>, you may index either the keys or the values. If the column identifier is placed within the keys() function, the index will be on the map keys, allowing you to use CONTAINS KEY in WHERE clauses. Otherwise, the index will be on the map values.


Dropping a secondary index uses the DROP INDEX statement:

drop_index_statement::= DROP INDEX [ IF EXISTS ] index_name

The DROP INDEX statement is used to drop an existing secondary index. The argument of the statement is the index name, which may optionally specify the keyspace of the index.

If the index does not exists, the statement will return an error, unless IF EXISTS is used in which case the operation is a no-op.