Thread

1. problem with fe/be protocol and large objects

   Eric Marsden <emarsden@mail.dotcom.fr> — 2001-03-11T21:24:43Z

   I am trying to debug my socket-level interface to the backend, which
   implements the 6.4 protocol. It works for general queries, but I have
   a problem with large objects.
   
   lo_create and lo_unlink seem to work OK; I get an oid which looks ok
   and there is a corresponding xinv??? file in the base/ directory.
   lo_open returns 0 as a file descriptor. However, following up with one
   of the other lo functions which take descriptor arguments (such as
   lo_write or lo_tell) fails with
   
      ERROR:  lo_tell: invalid large object descriptor (0)
   
   Looking at be-fsstubs.c it seems that this arises when cookies[fd] is
   NULL. I don't know what this might come from: the lo_tell is sent
   right after the lo_open, on the same connection.
   
   Running the sample lo program in C works, so I suppose the problem
   must come from the bytes I'm sending. Any ideas what could cause this? 
   
   
   PostgreSQL 7.0.3 on sparc-sun-solaris2.5.1, compiled by gcc 2.95.2
   
   -- 
   Eric Marsden                          <URL:http://www.laas.fr/~emarsden/>
   
   

2. Re: problem with fe/be protocol and large objects

   Denis Perchine <dyp@perchine.com> — 2001-03-13T15:15:17Z

   On Monday 12 March 2001 03:24, Eric Marsden wrote:
   > I am trying to debug my socket-level interface to the backend, which
   > implements the 6.4 protocol. It works for general queries, but I have
   > a problem with large objects.
   >
   > lo_create and lo_unlink seem to work OK; I get an oid which looks ok
   > and there is a corresponding xinv??? file in the base/ directory.
   > lo_open returns 0 as a file descriptor. However, following up with one
   > of the other lo functions which take descriptor arguments (such as
   > lo_write or lo_tell) fails with
   >
   >    ERROR:  lo_tell: invalid large object descriptor (0)
   
   You should do ANY operations with LOs in transaction.
   
   > Looking at be-fsstubs.c it seems that this arises when cookies[fd] is
   > NULL. I don't know what this might come from: the lo_tell is sent
   > right after the lo_open, on the same connection.
   >
   > Running the sample lo program in C works, so I suppose the problem
   > must come from the bytes I'm sending. Any ideas what could cause this?
   >
   >
   > PostgreSQL 7.0.3 on sparc-sun-solaris2.5.1, compiled by gcc 2.95.2
   
   -- 
   Sincerely Yours,
   Denis Perchine
   
   ----------------------------------
   E-Mail: dyp@perchine.com
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3. Re: problem with fe/be protocol and large objects

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-03-13T15:52:27Z

   Eric Marsden <emarsden@mail.dotcom.fr> writes:
   > lo_open returns 0 as a file descriptor. However, following up with one
   > of the other lo functions which take descriptor arguments (such as
   > lo_write or lo_tell) fails with
   
   >    ERROR:  lo_tell: invalid large object descriptor (0)
   
   Are you remembering to wrap this sequence in a transaction block
   (begin/end)?  LO descriptors are only valid till end of transaction.
   
   			regards, tom lane
   
   

4. Re: problem with fe/be protocol and large objects

   Eric Marsden <emarsden@mail.dotcom.fr> — 2001-03-13T16:31:33Z

   >>>>> "tl" == Tom Lane <tgl@sss.pgh.pa.us> writes:
   
     ecm> ERROR:  lo_tell: invalid large object descriptor (0)
   
     tl> Are you remembering to wrap this sequence in a transaction block
     tl> (begin/end)? LO descriptors are only valid till end of
     tl> transaction.
   
   that was it, thanks. The code used to work with PostgreSQL 6.3, and I
   hadn't seen the relevant warning in the programmer's guide.
   
   -- 
   Eric Marsden                          <URL:http://www.laas.fr/~emarsden/>