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Re: Add-if-not-present

> masarati@aero.polimi.it wrote:
>> I need to implement a modify operation whose semantics is "add if not
>> present", an add that only takes place if that attribute is not yet
>> present in the entry.
>> I need it as an internal operation, so right now I wouldn't bother
>> formalizing it as an extension of the semantics of the modify operation.
>> Something like the SLAP_MOD_SOFTADD, which in turn consists in adding an
>> attribute value only if that value is not already present.
>> I'd introduce a SLAP_MOD_ADD_IF_NOT_PRESENT flag and add code to support
>> it in all (well, most) backends/overlays that need to muck with modify
>> operation type.
> Sounds like you could do it with an Assertion Control (!(attr=*)).

Well, I already considered the possibility to combine already existing
semantics; however, there are two good reasons not to use that:

1) if the assertion fails, the operation needs to be resubmitted

2) there might already be an assertion control on the request