DROP INDEX

Removes an index.

Synopsis

DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <name> [, ...] [ CASCADE | RESTRICT ]

DROP INDEX drops an existing index from the database system. To run this command you must be the owner of the index.

CONCURRENTLY: Drop the index without locking out concurrent selects, inserts, updates, and deletes on the index’s table. A normal DROP INDEX acquires an exclusive lock on the table, blocking other accesses until the index drop can be completed. With this option, the command instead waits until conflicting transactions have completed.; There are several caveats to be aware of when using this option. Only one index name can be specified, and the CASCADE option is not supported. (Thus, an index that supports a UNIQUE or PRIMARY KEY constraint cannot be dropped this way.) Also, regular DROP INDEX commands can be performed within a transaction block, but DROP INDEX CONCURRENTLY cannot.
IF EXISTS: Do not throw an error if the index does not exist. A notice is issued in this case.
name: The name (optionally schema-qualified) of an existing index.
CASCADE: Automatically drop objects that depend on the index.
RESTRICT: Refuse to drop the index if any objects depend on it. This is the default.

Remove the index title_idx:

DROP INDEX title_idx;

DROP INDEX is a Greenplum Database language extension. There are no provisions for indexes in the SQL standard.