MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
DROP INDEX [ONLINE | OFFLINE]index_name
ONtbl_name
[algorithm_option
|lock_option
] ...algorithm_option
: ALGORITHM [=] {DEFAULT | INPLACE | COPY}lock_option
: LOCK [=] {DEFAULT | NONE | SHARED | EXCLUSIVE}
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. See Section 13.1.7, “ALTER TABLE Statement”.
To drop a primary key, the index name is always
PRIMARY
, which must be specified as a quoted
identifier because PRIMARY
is a reserved word:
DROP INDEX `PRIMARY` ON t;
Indexes on variable-width columns of
NDB
tables are dropped online; that
is, without any table copying. The table is not locked against
access from other NDB Cluster API nodes, although it is locked
against other operations on the same API node
for the duration of the operation. This is done automatically by
the server whenever it determines that it is possible to do so;
you do not have to use any special SQL syntax or server options to
cause it to happen.
In NDB Cluster, you can drop indexes offline (which causes the
table to be locked for all API nodes in the cluster) using the
OFFLINE
keyword. The rules and limitations
governing DROP OFFLINE INDEX
and DROP
ONLINE INDEX
are the same as for ALTER OFFLINE
TABLE ... DROP INDEX
and ALTER ONLINE TABLE ...
DROP INDEX
. You cannot cause the noncopying dropping of
an index that would normally be dropped offline by using the
ONLINE
keyword: If it is not possible to
perform the DROP
operation without table
copying, the server ignores the ONLINE
keyword.
For more information, see
Section 18.5.11, “Online Operations with ALTER TABLE in NDB Cluster”.
The ONLINE
and OFFLINE
keywords are available only in NDB Cluster; attempting to use
these keywords in standard MySQL Server 5.6 releases
results in a syntax error. The ONLINE
and
OFFLINE
keywords are deprecated in MySQL NDB
Cluster 7.3; they continue to be supported in MySQL NDB Cluster
7.4, but are scheduled for removal in a future NDB Cluster
release.
ALGORITHM
and LOCK
clauses
may be given to influence the table copying method and level of
concurrency for reading and writing the table while its indexes
are being modified. They have the same meaning as for the
ALTER TABLE
statement. For more
information, see Section 13.1.7, “ALTER TABLE Statement”