Sequences
Hi All,
I am using a sequence to automatically generate a transaction number in
my database. I've set up the transaction number to have a default value
from the sequence, so that I don't have to provide a number while
entering. However, I want to know the number of the transaction I've
just entered. I can do that by calling curval(sequence), but in a
dynamic situation with lot of transactions being recorded by multiple
users, how can I be sure I am getting the value which I had entered.
It sounds silly, but I am sure there is a simple solution for it. Do I
have to lock the sequence while I am using so that no one else can use
it, or do I fire both the queries in the same TRANSACTION block?
Thanks for any help,
Anand.
Exactly. I want to do the same thing, but don't know of any better way. Can
you check the tuple which has just been inserted?
Thanks,
Anand
Fran Fabrizio wrote:
Show quoted text
Correct me if I am wrong, but you are inserting the value of this sequence
into a table for the transaction you've just processed, right? So instead
of accessing the current value of the sequence, can't you just access the
transaction number that got insterted into the table?At 04:15 PM 10/20/98 -0700, you wrote:
Hi All,
I am using a sequence to automatically generate a transaction number in
my database. I've set up the transaction number to have a default value
from the sequence, so that I don't have to provide a number while
entering. However, I want to know the number of the transaction I've
just entered. I can do that by calling curval(sequence), but in a
dynamic situation with lot of transactions being recorded by multiple
users, how can I be sure I am getting the value which I had entered.
It sounds silly, but I am sure there is a simple solution for it. Do I
have to lock the sequence while I am using so that no one else can use
it, or do I fire both the queries in the same TRANSACTION block?
Thanks for any help,
Anand.
Import Notes
Reference msg id not found: 3.0.6.32.19981020183130.007a1380@mail.primary.net | Resolved by subject fallback
At 1:15 +0200 on 21/10/98, Anand Surelia wrote:
I am using a sequence to automatically generate a transaction number in
my database. I've set up the transaction number to have a default value
from the sequence, so that I don't have to provide a number while
entering. However, I want to know the number of the transaction I've
just entered. I can do that by calling curval(sequence), but in a
dynamic situation with lot of transactions being recorded by multiple
users, how can I be sure I am getting the value which I had entered.
It sounds silly, but I am sure there is a simple solution for it. Do I
have to lock the sequence while I am using so that no one else can use
it, or do I fire both the queries in the same TRANSACTION block?
Thanks for any help,
The following is from the "create_sequence" manpage:
After sequence created, You may use function nextval with
sequence name as argument to get new number from sequence
specified. Function currval ('sequence_name') may be used
to determine number returned by last call to nextval for
specified sequence in current session.
When they say "current session", they mean "the connection we are working
with in the current process".
That is, if your client uses a connection, and this connection has used
nextval (within the default clause, invoked by an insert), the call to
currval will *always* relate to that specific nextval. Even if three
hundred other processes have inserted lines and received their own nextval,
they will each have a different value to currval - the value they, and only
they, have created.
So, unless you have a connection shared between multiple threads of the
same process or something on the client side, currval is the right thing to
use, with no fear.
Herouth
--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma