Syntax
------ 
DROP INDEX [IF EXISTS] index_name ON tbl_name 
 [WAIT n |NOWAIT]
 [algorithm_option | lock_option] ...
 
algorithm_option:
 ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}
 
lock_option:
 LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}
 
Description
----------- 
DROP INDEX drops the index named index_name from the table
tbl_name.
This statement is mapped to an ALTER TABLE statement to drop
the
index.
 
If another connection is using the table, a metadata lock is
active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
 
See ALTER TABLE.
 
Another shortcut, CREATE INDEX, allows the creation of an
index.
 
To remove the primary key, `PRIMARY` must be specified as
index_name. Note that the quotes are necessary, because
PRIMARY is a keyword.
 
Privileges
 
Executing the DROP INDEX statement requires the INDEX
privilege for the table or the database.
 
Online DDL
 
In MariaDB 10.0 and later, online DDL is supported with the
ALGORITHM and LOCK clauses.
 
See InnoDB Online DDL Overview for more information on
online DDL with InnoDB.
 
DROP INDEX IF EXISTS ...
 
The IF EXISTS clause was added in MariaDB 10.1.4.
 
If the IF EXISTS clause is used, then MariaDB will return a
warning instead of an error if the index does not exist.
 
WAIT/NOWAIT
 
Set the lock wait timeout. See WAIT and NOWAIT.
 
ALGORITHM
 
See ALTER TABLE: ALGORITHM for more information.
 
LOCK
 
See ALTER TABLE: LOCK for more information.
 
Progress Reporting
 
MariaDB provides progress reporting for DROP INDEX statement
for clients
that support the new progress reporting protocol. For
example, if you were using the mysql client, then the
progress report might look like this::
 


URL: https://mariadb.com/kb/en/drop-index/