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PostgreSQL, ODBC and long strings: msg#00028

Subject: PostgreSQL, ODBC and long strings
Further to my earlier post I have done some investigating. It turns out the problems is with all strings greater than 255 characters which are automatically converted to LO.

The statement of the form

cursor.execute("SELECT value FROM table WHERE x = ?", (a_value, ))

where a_value is a string longer than 255 characters always generates an error of the form
ProgrammingError: ('HY000', 7, 'ERROR:  type "lo" does not exist', 5898)

The ODBC.log

STATEMENT ERROR: func=SC_execute, desc='', errnum=7, errmsg='Error while executing the query'
                 ------------------------------------------------------------
                 hdbc=28785640, stmt=28779072, result=28813312
                 manual_result=0, prepare=1, internal=0
                 bindings=0, bindings_allocated=0
                 parameters=28817032, parameters_allocated=1
statement_type=0, statement='SELECT id FROM localekit_attributes where attribute = ?' stmt_with_params='SELECT id FROM localekit_attributes where attribute = '829028'::lo'
                 data_at_exec=-1, current_exec_param=-1, put_data=0
                 currTuple=-1, current_col=-1, lobj_fd=-1
maxRows=0, rowset_size=1, keyset_size=0, cursor_type=0, scroll_concurrency=1
                 cursor_name='SQL_CUR01B72240'
----------------QResult Info ------------------------------- fields=28815040, manual_tuples=0, backend_tuples=0, tupleField=0, conn=0 fetch_count=0, num_total_rows=0, num_fields=0, cursor='(NULL)' message='ERROR: operator does not exist: text = lo', command='(NULL)', notice='(NULL)'
                 status=7, inTuples=0
CONN ERROR: func=SC_execute, desc='', errnum=110, errmsg='ERROR: type "lo" does not exist'
            ------------------------------------------------------------
            henv=28785584, conn=28785640, status=1, num_stmts=16
            sock=28778336, stmts=28815080, lobj_type=-999
            ---------------- Socket Info -------------------------------
            socket=600, reverse=0, errornumber=0, errormsg='(NULL)'
            buffer_in=34283600, buffer_out=34291800
            buffer_filled_in=11, buffer_filled_out=0, buffer_read_in=11

It seems that the ODBC driver is not returning enough information about the datatype text and that the Python ODBC driver is automatically converting to a large object for strings more than 255 characters in length.

What possible solutions are there to this problem? defining the lo type? or improving the information provided by the ODBC driver?

Thanks for any pointers

Charlie
--
Charlie Clark
Helmholtzstr. 20
Düsseldorf
D-40215
Tel: +49-211-938-5360
GSM: +49-178-782-6226

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