How do I create an index from a stored procedure or create index on every table in MySQL?

Question

These are two things that I've tried so far, along with their error messages:

DELIMITER //

CREATE PROCEDURE createModifiedIndex(t varchar(256))
  BEGIN
    declare idx varchar(256);
    DECLARE i int;
    declare makeIndexSql varchar(256);
    set idx = concat('idx_', t, '_modified_on');
    set i = (select count(*) from INFORMATION_SCHEMA.STATISTICS where table_name = t and index_name = idx);
    if i > 0 then
        set makeIndexSql = concat('create index ', idx, ' on ', t, ' (modified_on);');
        prepare stmt from makeIndexSql;
        execute stmt;
    end if;
  END //

DELIMITER ;

call createModifiedIndex ('ACHDebitFrequencies');
call createModifiedIndex ...

ERROR 1064 (42000) at line 5: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'makeIndexSql; execute stmt; end if; END' at line 10

This is another different attempt but won't work because MySQL doesn't allow IF/THEN outside of stored procedures.

set @i = (select count(*) from INFORMATION_SCHEMA.STATISTICS where table_name = 'ACHDebitFrequencies' and index_name = 'idx_ACHDebitFrequencies_modified_on');
if @i > 0 then begin
        create index 'idx_ACHDebitFrequencies_modified_on' on ACHDebitFrequencies (modified_on);
end;
end if;
...

ERROR 1064 (42000) at line 3: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'if @i > 0 then begin create index 'idx_ACHDebitFrequencies_modified_on' on ACHD' at line 1

Version mysql-5.1.62-r1

Answer 1

The core problem with your procedure was that PREPARE statement only works with a user variable or a string literal. It can't prepare a statement from a procedure variable.

PREPARE Syntax
PREPARE stmt_name FROM preparable_stmt
... preparable_stmt is either a string literal or a user variable that contains the text of the SQL statement.

DELIMITER //
CREATE PROCEDURE createModifiedIndex(t VARCHAR(256))
  BEGIN
    DECLARE idx VARCHAR(256);
    DECLARE i INT;

    SET idx = CONCAT('idx_', t, '_modified_on');
    SET i = (SELECT COUNT(*) FROM INFORMATION_SCHEMA.STATISTICS WHERE table_name = t AND index_name = idx);
    IF i = 0 THEN
        SET @makeIndexSql = CONCAT('CREATE INDEX ', idx, ' ON ', t, ' (modified_on);');
        PREPARE stmt FROM @makeIndexSql;
        EXECUTE stmt;
        DEALLOCATE PREPARE stmt; -- Use DEALLOCATE when you're done with the statement
    END IF;
  END //

DELIMITER ;