Limiting mysql table to a sertain size and automatically deleting oldest entries [duplicate]

Question

Possible Duplicate:
How can I set a maximum number of rows in MySQL table?

Is it possible ( and how ) to put a limit on a MySQL table ( let's say 100'000 ) and deleting the old entries when limit reaches?

Meaning, when I have 100'000 entries and the 100'001 appears, the entry with the smallest ID is deleted and the new one is created ( with the new ID of course ).

I want MySQL to handle this on it's own, so no outside scripts need to interfere.

I need this for logging purposes, meaning, I want to keep logs only for a certain time period, let's say a week. Maybe it is possible for MySQL just to delete entries, that are older then 1 week on it's own?

Answer 1

I propose triggers. This is the best way of insuring that at each insert the maximum table size is being taken into account.

Possible duplicate of How can I set a maximum number of rows in MySQL table?

From that accepted answer:

---

Try to make a restriction on adding a new record to a table. Raise an error when a new record is going to be added.

DELIMITER $$

CREATE TRIGGER trigger1
BEFORE INSERT
ON table1
FOR EACH ROW
BEGIN
  SELECT COUNT(*) INTO @cnt FROM table1;
  IF @cnt >= 25 THEN
    CALL sth(); -- raise an error
  END IF;
END
$$

DELIMITER ;

Note, that COUNT operation may be slow on big InnoDb tables.

On MySQL 5.5 you can use SIGNAL statement to raise an error.