On Fri, 14 Nov 2014, Marcos Douglas wrote:
By the very nature of the problem: GetLastAutoIncValue simply cannot be
implemented in general.
In firebird, postgres, these values are generated using a
generator/sequence.
...as well as could have a trigger for these cases, encapsulating the
"problem" in database... but the code in these cases should be
different.
I know. RETURNING will handle this case correctly.
You don't know the name of the generator, and even if you did, it is
impossible to retrieve the value that was used to fill your particular
record because the sequence/generator may have been updated several
thousands of times by the time your second statement arrives.
If you use a sequence/generator, you should call it before INSERT.
That is one way, but not obligatory. Mostly it is done in triggers.
This is not a problem. RETURNING handles all cases.
If you use auto-inc, the DMBS have support to return the last id on
your session.
I know.
The only way to do this correctly is using a RETURNING clause when doing the
insert.
This RETURNING clause works for all DBMS?
AFAIK Only sqlite does not (maybe it does today).
But that is not a DBMS :-)
The idea is to add [pfRefresh] to providerflags. When doing an insert, the
fields with this flag will be added to the RETURNING clause and used to
update the buffer.
Fields of type ftautoInc can be added to this list (i.e. they automatically
get pfRefresh in their providerflags)
This approach will work on all SQL databases that support RETURNING.
(That should include any SQL database available today)
Nice. But this is only a part of code. How do you will get the last ID
and put in record?
This is the complete code, because the "returning" clause will contain the ID.
Your remarks sound like maybe you don't understand/know exactly what RETURNING
does ?
It was invented exactly to deal with such things.
Michael.
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