IGNORE INDEX

Syntax

IGNORE INDEX [{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])

Description

You can tell the optimizer to not consider a particular index with the IGNORE INDEX option.

The benefit of using IGNORE_INDEX instead of USE_INDEX is that it will not disable a new index which you may add later.

Also see Ignored Indexes for an option to specify in the index definition that indexes should be ignored.

Index Prefixes

When using index hints (USE, FORCE or IGNORE INDEX), the index name value can also be an unambiguous prefix of an index name.

Example

This is used after the table name in the FROM clause:

CREATE INDEX Name ON City (Name);
CREATE INDEX CountryCode ON City (Countrycode);
EXPLAIN SELECT Name FROM City IGNORE INDEX (Name)
WHERE name="Helsingborg" AND countrycode="SWE";

This produces:

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	City	ref	CountryCode	CountryCode	3	const	14	Using where

See Also

• See Index Hints: How to Force Query Plans for more details

• USE INDEX

• FORCE INDEX

• Ignored Indexes

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