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RE: [SQL] Re: [INTERFACES] JDBC and getting just assigned serial number

From: "Hutton, Rob" <HuttonR(at)plymart(dot)com>
To: "'Herouth Maoz'" <herouth(at)oumail(dot)openu(dot)ac(dot)il>, steinbeck(at)ice(dot)mpg(dot)de, pgsql-interfaces(at)postgreSQL(dot)org
Cc: pgsql-sql(at)postgreSQL(dot)org
Subject: RE: [SQL] Re: [INTERFACES] JDBC and getting just assigned serial number
Date: 1999-09-22 16:21:53
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfacespgsql-sql
  Except in an active database, or possibly not so active, where another
record is inserted between the time yours is committed and you do the
currval.  It is much safer to do a select on nextval to get the value, the
put it in as part of your update.  It eliminates the chance that you will
get the wrong record, and there is minimal overhead.

-----Original Message-----
From: Herouth Maoz [mailto:herouth(at)oumail(dot)openu(dot)ac(dot)il]
Sent: Wednesday, September 22, 1999 11:17 AM
To: steinbeck(at)ice(dot)mpg(dot)de; pgsql-interfaces(at)postgreSQL(dot)org
Cc: pgsql-sql(at)postgreSQL(dot)org
Subject: [SQL] Re: [INTERFACES] JDBC and getting just assigned serial

At 21:19 +0200 on 13/09/1999, Christoph Steinbeck wrote:

> I'm thrilled to see that there is some kind of discussion running in the
> C area on the exact equivalent of my very recent JDBC problem.
> I insert a row into a table where one field is a SERIAL. This SERIAL, of
> course, is automatically assigned by PostgreSQL. How do I get this
> number immeadiately after inserting the row? When I issue the command
> with psql I get back some kind of number which presumably is the OID.
> Getting just this one would be fine too because I need it for
> referencing.

I have answered this question several times already on the SQL list. It has
nothing to do with Java or any other interface you are using (except,
maybe, the question about how to get the OID).

Let's make it short.

1) Don't use OIDs for reference. It will only make life harder.

2) If you want to use the OID just to retrieve that last row, make sure
   that the OID column is indexed, otherwise you are in for sequential
   searching. See, I told you not to use it...

3) As for the serial field. "serial" is a shorthand notation for
   creating an PostgreSQL sequence, and taking the next number from
   that sequence. You can see the name of the sequence that was
   created with a quick \ds in psql.

   Now, after inserting a row, use SELECT currval('sequence_name');
   The number returned is the number assigned to the serial number in
   the last INSERT statement of the current session.


Herouth Maoz, Internet developer.
Open University of Israel - Telem project

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