Documentation Home
MySQL 8.0 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 44.5Mb
PDF (A4) - 44.5Mb
PDF (RPM) - 40.2Mb
HTML Download (TGZ) - 10.5Mb
HTML Download (Zip) - 10.5Mb
HTML Download (RPM) - 9.1Mb
Man Pages (TGZ) - 204.6Kb
Man Pages (Zip) - 311.6Kb
Info (Gzip) - 3.9Mb
Info (Zip) - 3.9Mb
Excerpts from this Manual

13.1.27 DROP INDEX Syntax

DROP INDEX index_name ON tbl_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 13.1.9, “ALTER TABLE Syntax”.

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.

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 13.1.9, “ALTER TABLE Syntax”

MySQL NDB Cluster supports online operations using the same ALGORITHM=INPLACE syntax supported in the standard MySQL Server. See Section 13.1.9.2, “ALTER TABLE Online Operations in NDB Cluster”, for more information.


User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
  Posted by Tim Tribe on November 18, 2011
How long would you expect a drop index to take?
Think again!

It can easily run into tens of minutes if not hours!!(on innodb, at least), during which time other operation can be impacted.
So use with care on live production servers!
Sign Up Login You must be logged in to post a comment.