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Re: [INTERFACES] ODBC, Delphi and BLOBs (images)

From: "Andrzej Szydlo" <andrzej(at)gv(dot)edu(dot)pl>
To: Byron Nikolaidis <byronn(at)insightdist(dot)com>
Cc: pgsql-interfaces(at)hub(dot)org
Subject: Re: [INTERFACES] ODBC, Delphi and BLOBs (images)
Date: 1998-08-19 19:36:49
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfaces

Thanks for your help.

I still cannot solve this problem. The real problem is that Delphi 
doesn't send a BLOB to the database. In logs there is not even a 
trace of any INSERT o UPDATE attempt. When images are already in the 
table (inserted there in any other way) Delphi displays them 

I suspect the real cause is confused BDE or confused 
Delphi. One of the BLOB field properties in the Delphi's Object 
Inspector is "Size", which means the size of the BLOB portion stored 
in a table directly. For the "lo" type the Size should be 0, I guess, 
since it doesn't store any BLOB data directly in a table. Delphi 
"sees" the lo (LongVarBinary) Size is 1 and when I change it to any 
other value, it complains "Field 'img' is not of the expected type". 
The Database Explorer doesn't show any "Size" property for lo fields, 
the BLOB fields form other databases usually (haven't checked all 
yet) have this property. Do you think it might cause the problem? If 
so, how could I change it?

Any suggestions welcome.


On Tue, 18 Aug 1998 at 15:34:44 -0400, Byron Nikolaidis wrote:

> It seems that the error handling in the _SQLFetch routine was a little
> behind the times, which is confusing things even more and producing the
> "unrecognized return value from copy_and_convert...".
> I have fixed the error handling code so that it should hopefully return a
> better description of the problem.
> FYI, there are three possibilities that can cause the 0 to appear:
> 1. The large object couldn't be opened
> 2. The large object couldn't be read
> 3. Something is wrong/incompatible with the multiple GetData calls.
> I'm gonna send you the new driver with the better error handling to try in
> another mailing.
> Byron
> Andrzej Szydlo wrote:
> > Hello,
> >
> > I'm trying to access PostgreSQL database from Delphi via ODBC.
> > Everything works fast and reliably. The only problem are BLOBs,
> > images in this case.
> >
> > I created the "lo" type according to the FAQ:
> >
> >      create type lo (
> >      internallength=4,  externallength=10,
> >      input=int4in, output=int4out,
> >      default='',  passedbyvalue
> >      );
> >
> > and then created a table and an index:
> >
> > CREATE TABLE test_tab(nr int4, img lo);
> > CREATE UNIQUE INDEX test_inx ON test_tab (nr);
> >
> > I attached a DBImage control to the "img" field and DBEdit to "nr"
> >
> > When I insert "images" to the table manually, later  Delphi displays
> > it without any problem.
> >
> > When I try to insert any image from Dephi, the value "0" is inserted
> > instead of any real OID value, which causes:
> >
> >  "Unrecognized return value from copy_and_convert_field."
> >
> > on a select attempt.
> >
> > What can cause "0" to be inserted instead of any value, say 16648?
> > Have anyone ever had similar problem? How can it be solved?
> >
> > It seems that the problem is caused by the Delphi-ODBC interaction.
> > With Access everything works well.
> >
> > If the information I gave here is not precise enough or unclear,
> > please ask me for any extra details.
> >
> > I'd appreciate any suggestions pointing me to the right direction.


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Next:From: Andrzej SzydloDate: 1998-08-19 21:53:54
Subject: Re: [INTERFACES] ODBC, Delphi and BLOBs (images)
Previous:From: Byron NikolaidisDate: 1998-08-19 18:31:38
Subject: Re: [INTERFACES] iodbc interface on Unix

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