Обсуждение: SELECT INTO TEMPORARY problem

I have a servlet which gets its data through a DataSource (Tomcat 5.5)
and starts each request as a new SQL transaction and either commits
the transaction or rolls it back at the end of each request.

In one of the requests I do a SELECT ... INTO TEMPORARY t1 ..., which
works just fine when I first use it, but from then on it objects saying
that t1 already exists.  When I read the documentation (8.1 as that is
what I am using) I thought I understood that the table would disappear
at the end of the transaction.  Other than deleting it, is there something
else I need to do or have I missunderstood that into temporary does?

David

David Goodenough <david.goodenough@btconnect.com> writes:
> In one of the requests I do a SELECT ... INTO TEMPORARY t1 ..., which
> works just fine when I first use it, but from then on it objects saying
> that t1 already exists.  When I read the documentation (8.1 as that is
> what I am using) I thought I understood that the table would disappear
> at the end of the transaction.

No, the default is to last until end of session.

There's an ON COMMIT DROP option in the CREATE TEMP TABLE syntax,
but I don't think it's possible to stick it into an INTO TEMP clause.

            regards, tom lane

David Goodenough wrote:
> I thought I understood that the table would disappear
> at the end of the transaction.  Other than deleting it, is there something
> else I need to do or have I missunderstood that into temporary does?

Dropped when the connection is closed normally, but see the ON COMMIT.

http://www.postgresql.org/docs/8.1/static/sql-createtable.html

You might have to do CREATE TABLE then INSERT INTO ... SELECT though.

--
   Richard Huxton
   Archonet Ltd

am  Wed, dem 17.01.2007, um 16:04:10 +0000 mailte David Goodenough folgendes:
> I have a servlet which gets its data through a DataSource (Tomcat 5.5)
> and starts each request as a new SQL transaction and either commits
> the transaction or rolls it back at the end of each request.
>
> In one of the requests I do a SELECT ... INTO TEMPORARY t1 ..., which
> works just fine when I first use it, but from then on it objects saying
> that t1 already exists.  When I read the documentation (8.1 as that is
> what I am using) I thought I understood that the table would disappear
> at the end of the transaction.  Other than deleting it, is there something
> else I need to do or have I missunderstood that into temporary does?

known problem, FAQ. Use EXECUTE for your DDL-Statements.

http://www.postgresql.org/docs/faqs.FAQ.html#item4.19



Andreas
--
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net

On 1/17/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> David Goodenough <david.goodenough@btconnect.com> writes:
> > In one of the requests I do a SELECT ... INTO TEMPORARY t1 ..., which
> > works just fine when I first use it, but from then on it objects saying
> > that t1 already exists.  When I read the documentation (8.1 as that is
> > what I am using) I thought I understood that the table would disappear
> > at the end of the transaction.
>
> No, the default is to last until end of session.
>
> There's an ON COMMIT DROP option in the CREATE TEMP TABLE syntax,
> but I don't think it's possible to stick it into an INTO TEMP clause.
>
>                        regards, tom lane
>

IIRC, you can do it using CREATE TEMP TABLE t1 ON COMMIT DROP AS query
but i think this new in 8.2

why not extending this to SELECT INTO TEMP?

--
regards,
Jaime Casanova

"Programming today is a race between software engineers striving to
build bigger and better idiot-proof programs and the universe trying
to produce bigger and better idiots.
So far, the universe is winning."
                                       Richard Cook