MySQL elimina todos los índices de la tabla

Solución:

Guión simple:

-- list all non-unique indexes
SELECT table_name AS `Table`,
       index_name AS `Index`,
       GROUP_CONCAT(column_name ORDER BY seq_in_index) AS `Columns`
FROM information_schema.statistics
WHERE NON_UNIQUE = 1 AND table_schema="mydatabase" AND table_name="mytable"
GROUP BY 1,2;

-- drop all non-unique indexes
SET SESSION group_concat_max_len=10240;

SELECT CONCAT('ALTER TABLE ', `Table`, ' DROP INDEX ', GROUP_CONCAT(`Index` SEPARATOR ', DROP INDEX '),';' )
FROM (
SELECT table_name AS `Table`,
       index_name AS `Index`
FROM information_schema.statistics
WHERE NON_UNIQUE = 1 AND table_schema="mydatabase" AND table_name="mytable"
GROUP BY `Table`, `Index`) AS tmp
GROUP BY `Table`;

-- add all non-unique indexes , WITHOUT index length spec
SET SESSION group_concat_max_len=10240;
SELECT CONCAT('ALTER TABLE ', `Table`, ' ADD INDEX ', GROUP_CONCAT(CONCAT(`Index`, '(', `Columns`, ')') SEPARATOR ',n ADD INDEX ') )
FROM (
SELECT table_name AS `Table`,
       index_name AS `Index`,
        GROUP_CONCAT(column_name ORDER BY seq_in_index) AS `Columns`
FROM information_schema.statistics
WHERE NON_UNIQUE = 1 AND table_schema="mydatabase" AND table_name="mytable"
GROUP BY `Table`, `Index`) AS tmp
GROUP BY `Table`;

Si tiene phpmyadmin o cualquier herramienta similar, puede hacerlo muy fácilmente gráficamente.

O para cada índice haga algo como

ALTER TABLE  `table` DROP INDEX  `NameIndex`

Puede obtener los índices con

SHOW INDEX FROM `table`

En Ruby on Rails hago esto:

indexes = ActiveRecord::Base.connection.execute("SHOW INDEX FROM tablename")
indexes.each do |index|
  ActiveRecord::Base.connection.execute("ALTER TABLE tablename DROP INDEX #{index[2]};")
end

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