----- Original Message -----
Sent: Friday, January 14, 2005 9:27
AM
Subject: RE: [DUG] concurrent Interbase
Transactions
Hi
Phil
It
might be safer to have the generator giving you a new unique number (on
request, not in a trigger) and to use and insert that with the data in the
ExeQuery.
As
you indicated, when implemented in a trigger then your fetch, to get this
value, may come too late and you end up with somebody
else's number.
Cheers,
John
Hi everyone - hope you all had a good break.
Looks like summer has finally arrived (now that everyone's back at work)!
Anyway...
I'm using Firebird (and transactions) for the
first time. I'm connecting to a remote database via the Firebird Server with
no problems, but I have a question about transactions:
When I insert a new record, I use a trigger and
a generator to generate a new unique ID for the new record - I also query
the generator to see what the new value is that was returned by the trigger.
The code snippet is as follows:
orderTransaction.Active := True;
with
orderQuery do //insert the
record
begin
ExecQuery;
with
IBCurrentGeneratorValueQuery do //
this query fetches the current value of the
generator
try
Transaction := orderTransaction; // share the
same transaction as the
order
Open;
result:=FieldByName('newID').asInteger; // get the generator
value
except
result:=-1;
end;
orderTransaction.Commit;
end;
The question is, if multiple clients access the
database server at the same time, will IBCurrentGeneratorValueQuery still return the correct value,
or if another concurrent transaction on another thread increments the
generator, will this query return the wrong value?
When I was using MySQL (with PHP) I could use
mysql_insert_id() to query the new key value. I guess that if I
could get hold of the newly inserted row I could just get the field value,
but the same concurrency issue applies and I'm not sure how to get the
record I just inserted.
Cheers,
Phil.
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