Too many auto increments with ON DUPLICATE KEY UPDATE

问题

I have a basic table with columns:

id (primary with AI)
name (unique)
etc

If the unique column doesn't exist, INSERT the row, otherwise UPDATE the row....

INSERT INTO pages (name, etc)
VALUES
  'bob',
  'randomness'
ON DUPLICATE KEY UPDATE
 name = VALUES(name),
 etc = VALUES(etc)

The problem is that if it performs an UPDATE, the auto_increment value on the id column goes up. So if a whole bunch of UPDATES are performed, the id auto_increment goes through the roof.

Apparently it was a bug: http://bugs.mysql.com/bug.php?id=28781

...but I'm using InnoDB on mySQL 5.5.8 on shared hosting.

Other people having issues with no solution years ago: prevent autoincrement on MYSQL duplicate insert and Why does MySQL autoincrement increase on failed inserts?

Ideas on a fix? Have I maybe structured the database incorrectly somehow?

******EDIT****: It appears adding innodb_autoinc_lock_mode = 0 to your my.ini file fixes the problem but what options do I have for shared hosting?

******EDIT 2******: OK, I think my only option is to change to MyISAM as the storage engine. Being a mega mySQL newbie, I hope that doesn't cause many issues. Yeah?

回答1:

I don't think there is a way to bypass this behaviour of INSERT ... ON DUPLICTE KEY UPDATE.

You can however put two statements, one UPDATE and one INSERT, in one transaction:

START TRANSACTION ;

UPDATE pages
SET etc = 'randomness'
WHERE name = 'bob' ;

INSERT INTO pages (name, etc)
SELECT 
      'bob' AS name
    , 'randomness' AS etc 
FROM dual 
WHERE NOT EXISTS
      ( SELECT *
        FROM pages p
        WHERE p.name = 'bob'
      ) ;

COMMIT ;

回答2:

The on duplicate key functionality of MySQL is exactly the same as doing two separate queries, one to select, then one to either update the selected record, or insert a new record. Doing so programmatically is just as fast and will prevent this problem in the future as well as make your code more portable.

来源：https://stackoverflow.com/questions/9189102/too-many-auto-increments-with-on-duplicate-key-update

标签

mysql

auto-increment

on-duplicate-key