[Boulder Ruby Group] ar validations licking the balls

[Charlie Savage]

Peter Williams wrote:
> Tony Arcieri wrote:
>> If you could get a table level lock, then checking the uniqueness of a
>> value before performing an insert/update could be an atomic, as well as
>> performing a find_or_create_by type operation
> 
> This approach would work but I have a hard time imagining wanting to
> take the performance hit of a table lock on any operation that happens
> often enough to make this race condition a real issue.
> 
> A workable approach for the case of find_or_create is to enforce the
> uniqueness with a database constraint and do this in ruby code:
> 
>   1. do a find
>   2a. return the model object if you found it
>   2b. if it does not exist try to insert it
>   3a. if the insert succeeds return the new object
>   3b. if the insert fails re-run the find and return the result of
>       that.

Mostly the same idea (also does update), but hides the nastiness in a 
postgresql procedure:

http://www.varlena.com/GeneralBits/126.php

And I don't think it requires a savepoint.

Charlie
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