SQLDescribeParam / SUPPORT_DESCRIBE_PARAM

Hello,

I noticed that unixODBC logs IM001 SQL_ERRORs for SQLDescribeParam in
its tracefile. Actually, I first noticed the problem when I tried to use
a prepared statement in PHP 5.3.8 with a PostgreSQL 9.1 database and I
got error messages at odbc_execute() due to the SQLDescribeParam error.

First I thought that the problem is in PHPs ODBC extension because it
worked fine back in PHP-5.3.3. But digging into the sources of PHP I
found out, that the return value of SQLDescribeParam simply wasn't
validated before 5.3.5 (and there as no 5.3.4 release), but it returned
an IM001 SQL_ERROR ever since.

So following the chain I looked at the source of psqlodbc and noticed,
that the library is prepared for a database connection that supports
SQLDescribeParam and this is verified by SUPPORT_DESCRIBE_PARAM().

But what does it depend on, whether the connection supports it? psqlodbc
is for PostgreSQL only. I built the latest PostgreSQL library, compiled
the latest psqlodbc against it and SQLDescribeParam still threw the
IM001 SQL_ERROR.

As a quick fix just created a patch for PHP for my internal use, which
removes checking of the return values of SQLDescribeParam. But that
seems very odd. I'd really like to understand what's behind this issue.

Kind regards
Marten Lehmann