ODBC, large objects and tracing

Hi,

I am porting an application from Win NT to Linux. It is an application for 
storing, querying, subsetting and exporting geographic data. On NT the data 
is stored in MS SQL Server, database access is handled through a dll which 
handles all requests for data from the application. The dll is written using 
ODBC 3 as the interface to SQL Server.

I installed postgresql 6.53 a few days ago and had a go at getting the dll 
code working with the postgresql odbc driver. As the driver is written for 
odbc 2.0, I decided to try the UnixOdbc driver and driver manager. Using 
their package my code compiled perfectly, with NO modifications.

However, I immediatley ran into trouble when inserting into large-objects 
(Lot's of blobs in this app!). In the server trace there was an error to the 
effect of "Invalid large object descriptor".

That had me stumped until yesterday, when I ran across a patch for the ODBC 
driver on this mailing list (dated Dec. 8, 99). I applied the patch (by 
hand) to the UnixODBC version of the postgres driver, and the problem went 
away. I'm impressed! I thought it was going to be way more difficult than 
this.

If anyone is interested, I would be happy to supply the modified source 
files for the driver and a script I cobbled together to add the large object 
support functions, data type and table trigger (for deleting lo's). It all 
seems to work quite well.

I do have a couple of questions. What datatype does SQL_VARBINARY map to in 
postgresql? I searched the driver header files and came up with "bytea". But 
when I try to use it by binding my binary data to a parameter in the insert 
statement and then calling SQLExecute, SQLPutDate, etc., all I get is an 
SQL_ERROR return value from SQLExecute.

Finally, as lame as it sounds, I can't figure out how to make the odbc trace 
work! I've set TRACE = yes and specified a tracefile located in the postgres 
home directory. It is always empty. Have I missed something obvious?

Thanks,

Eliot Cline
IT Systems Manager
Intercontinental Sourcing and Services, Ltd.
Bangkok, Thailand
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