if create fails, it still auto increment

[bbc4468]

I have the following code

class SizeList
include Mongoid::Document
field :_id, type: Integer
field :name
auto_increment :sequence, :seed => -1, :step => 1
before_create { self.id = self.sequence }
end

I want the sequence to be continuous. This works really well, except in the case when create fails. It should decrease the sequence in such cases.

You should probably use after_add callback to increase the auto increment value.

Although i can still live with it.

[0sc]

Hi @proton, I'm looking to take this on. What do you think of changing https://github.com/proton/mongoid_auto_increment/blob/master/lib/mongoid_auto_increment.rb#L17 to after_create instead? That way the sequence is only generated when the DB persistence is confirmed

[proton]

@0sc can you tell me more?
If we just move this code to after_create it will create objects with nil id.

[0sc]

@proton my understanding is that if create fails the @@incrementor.inc(seq_name, options)) logic never executes and @@incrementor will remain in the state it was in before the creation was attempted. That way only valid/persisted get to have sequence assigned to them.

[proton]

@0sc so what you propose?

[0sc]

As per this issue, I suggest using after_create instead so that sequences are only assigned to records that will successfully be persisted.

[proton]

@0sc so you want make it in two transactions? I prefer keep atomicity.

[0sc]

I'm not sure I understand what you mean. Activerecord callbacks are executed within a single database transaction (See the transaction section here). Maybe I'm missing something but switching from before_create to after_create should not introduce another transaction

[proton]

@0sc it's not ActiveRecord :)

[0sc]

Ahh, my bad I was looking at the wrong docs.

But why will switching from before_create to after_create introduce another transaction in mongoid?

[proton]

There are no transactions in mongoid :3