Re: [Firebird-devel] "cannot update erased record" - handling

[Ivan P. <iva...@se...>]

"Dmitry Yemanov" wrote:
>> * It can be raised in the situation one would not expect it - normally
>>   the DELETE/UPDATE command either succeeds because
>>   it deletes/updates required record(s), or it succeeds because there is nothing
>>   to delete/update (e.g. delete from tab where 1=2;)
>>   But in described situation the DELETE can complain that record
>>   was already deleted - looks strange.
> 
> I kinda agree. But I think that all related issues should be solved as a 
> whole.

Yes, it would be nice, but not absolutely necessary, there already are situations
when different commands have different handling. Example from my post to fb-support:

  When one transaction locks (updates) row in Master table,
  then other transactions
    - can Update related rows in Detail table, but
    - can't Insert new Detail rows (referencing pk of locked row)


> For example, if the concurrent transaction has modified the 
> record, we need to re-fetch it and re-evaluate booleans.

Right, solving situation when concurrent transaction deletes
the record is easier, since there is nothing to re-fetch
(and it is what I had in mind, see Subject.)

>> * Could this error by avoided at all ? If the record was deleted,
>>   it means there is nothing to delete/update, so from users point of view
>>   the error has no sense.
>>   The only problem I see is with Before triggers that were already fired,
>>   can't they be just silently undone ?
> 
> I fail to see how the trigger actions could be undone for a single 
> record, sorry.

By creating internal savepoint ?  (but you know - I do not know the source code ...)

Ivan