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13.1.25 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 13.1.8, “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;

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 13.1.8, “ALTER TABLE Syntax”


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!
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