Re: JDBC: ERROR: portal "C_2" does not exist

Sorry, the email system wrapped some of my lines.  Here is a corrected version:

I have narrowed the problem down.  In pseudo code, here is what I am
trying to do (in my sample program):

conn.setAutoCommit(false)
PreparedStatement pstat = conn.prepareStatement(sql)
pstat.setFetchSize(50)
select all records in a large file
for each record:
        read one field from the record
        through a second statement, add a record to a different table - XXX
        execute the second statement - YYY
        commit the change - ZZZ
        loop

So, if I am just spinning through the records (not do XXX, YYY, and
ZZZ), it works.  But, I want to add records to a second table.  I need
the commit because I don't want thousands of new records in one
commit.  And, in terms of the reads, I want to read records 50 at a
time - not all at once.

It seems I can do one or the other but not both - or can I?

Thanks!

Blake

On Fri, Mar 11, 2022 at 9:45 PM Blake McBride  wrote:
>
> I have narrowed the problem down.  In pseudo code, here is what I am
> trying to do (in my sample program):
>
> conn.setAutoCommit(false)
> PreparedStatement pstat = conn.prepareStatement(sql)
> pstat.setFetchSize(50)
> select all records in a large file
> for each record:
>         read one field from the record
>         through a second statement, add a record to a different table   XXX
>         execute the second statement
>                  YYY
>         commit the change
>                         ZZZ
>         loop
>
> So, if I am just spinning through the records (not do XXX, YYY, and
> ZZZ), it works.  But, I want to add records to a second table.  I need
> the commit because I don't want thousands of new records in one
> commit.  And, in terms of the reads, I want to read records 50 at a
> time - not all at once.
>
> It seems I can do one or the other but not both - or can I?
>
> Thanks!
>
> Blake
>
>
>
> On Fri, Mar 11, 2022 at 1:56 PM Blake McBride  wrote:
> >
> > Thank you for the info, Sehrope!
> >
> > I checked. I am not closing anything.  However, I am using C3P0.  Perhaps that is configured wrong.  I'll look there.  Just knowing it should work is a big help.
> >
> > It is hard for me to give a sample because it is part of a larger system and I am using utilities in that system rather than raw JDBC.  However, I am the author of those utilities so it's not a blackbox.  (They're at https://github.com/blakemcbride/Kiss)
> >
> > Thank you!
> >
> > Blake
> >
> >
> >
> > On Fri, Mar 11, 2022 at 1:04 PM Sehrope Sarkuni  wrote:
> >>
> >> When auto commit is diabled and using a non-zero fetch size, the pgjdbc driver creates a portal to read the query results from the server in chunks of fetch size. The portals have a string identifier and the driver generates them sequentially per connection with a "C_" prefix, so "C_1", "C_2", "C_3", ... etc.
> >>
> >> As you read results via ResultSet.next(), the driver checks if it has the next row already buffered. If not, it reads from the named portal to retrieve the next chunk of fetchSize quantity of rows.
> >>
> >> A fetch size of 50 and the error happening at row 51 likely means that something either closed the portal or the connection itself is not correct.
> >>
> >> Are you using a connection pool like pgbouncer in between your Java application and the database server?
> >>
> >> If so, the connection pooler must be transaction aware to ensure that the same connection is used throughout the entire transaction.
> >>
> >> If not, try creating a minimal example that reproduces the error.
> >>
> >> Regards,
> >> -- Sehrope Sarkuni
> >> Founder & CEO | JackDB, Inc. | https://www.jackdb.com/
> >>
> >>
> >>