How to reuse auto_increment values? [duplicate]

Answer 1

It contains unique ids given to each thread for distinction.

You said that.
Unique id. For distinction.

How can you call an id unique?
What distinction it could be when today some topic has one id and a next day - another?
How can you find it back?
How you going to link it to other threads?

Try to think of these words meaning. It is called unique for the reason.

Try to think not as a child who wants "neat" and "cute" things just for the pleasure but as an adult, who can see the consequences.

Try to learn to listen to more experienced people and follow their knowledge and experience based advises, not only your whims.

Answer 2

I agree with the rest of everyone where it is a very bad idea to implement your own find minimal open number. But at where I work, we are given a closed set of number and when a number is free up, we must reuse.

Here is how we did it.

We do not delete the row, but set all values of every column null, So what you do is SELECT min(id) WHERE columnA IS NULL, and if this returns something, we reuse, otherwise, insert a new row.

Answer 3

Do yourself a favor and forget about this. It is going to be a massive pain to implement, so unless there is a very compelling goal to achieve that cannot be approached otherwise (unlikely) we are talking massive pain for no gain.

MySql itself does not support this scenario for exactly this reason: massive complication for no benefit.

Answer 4

MySQL will maintain the order of IDs unless the entire table is truncated. Deletion of rows does not affect the last ID.

Answer 5

So, for referential integrity I don't recommend re-using ids. With the maximum limits on int and bigint you should never run out of unique values. Unique values are the core of referential databases.

With that said, you could run a search sub-routine (or instead of trigger) to find the lowest available id. Then momentarily turn off identity inserts, insert the data, then turn identity inserts back on.

There are so many reasons not to do this! Among which are all of the potential collisions between inserting data when more than one value are coming in at the same time.

Answer 6

The maximum number of INT in MySQL 4294967295 if you are creating 1000 threads per minute you would need 1440000 ( 1000 x 60 x 24 ) id's per day. So you would run out of ids after about 8.17 years.

The maximum number of BIGINT is 18446744073709551615 and that would be enough to create 1000000000 (1 billion) ids per minute for 35 096 years.

So you should be fine with just wasting ids as much as you like and not worry about them.