NULL data not mapped to NA with RODBC on 64-bit Mac OS X
Hi Harlan, I suspect that we will need to wait for Prof. Ripley to be able to look into this further. There may be subtle issues at play here and I would defer to his more intimate knowledge of the ODBC tool chain. I do know that the Actual driver is both 32 and 64 bit in a single installation. However, I run R in 32 bit mode (don't need the extra address space, even though I now have 8Gb on my MacBook Pro), so have not encountered the 64 bit issues that you report here. I have the same header file. Note that SQLLEN is a signed declaration below. It is defined as a 'long' generally and as a INT64 for 64 bit Windows. It would be 'unsigned long' or UINT64, respectively for an unsigned value. One question for you however, which is do you know if you are booting the 32 bit or 64 bit OSX kernel on your Mac? Macs prior to mid-2010 (like mine) running Snow Leopard typically default to the 32 bit kernel, though can be 64 bit 'capable'. It depends upon various factors including the presence of a 64 bit EFI. Newer Macs now boot into the 64 bit kernel by default. I have seen some problems reported on older Macs where the default kernel was changed from 32 bit to 64 bit, resulting in subtle and not so subtle problems with some drivers. Booting to the 32 bit kernel still allows you to run 64 bit apps under Snow Leopard, just that the kernel and extensions are 32 bit. Regards, Marc
On Mar 23, 2011, at 2:29 PM, Harlan Harris wrote:
Any thoughts? Is there someone else or somewhere else I might ask? -Harlan On Tue, Mar 22, 2011 at 1:31 PM, Harlan Harris <harlan at harris.name> wrote:
Hello,
I seem to have hit a bug in RODBC on 64-bit versions of R on Mac OS X. I'm
running R 2.12.1, and using R to talk to Oracle and other databases using
RODBC 1.3-2. In 32-bit mode (R32), everything works. (The ODBC drivers are
the ones from Actual.) In 64-bit mode (R), it seems as if NULL data is not
being treated as missing. For example, a NULL value in an integer column is
being returned as a 0 instead, which is wrong/bad.
Diving into the code and Google a bit, it seems like an issue that's been
seen before in other contexts. Here's the relevant C code, from
RODBCFetchRows:
for(row = thisHandle->rowsUsed;
row < thisHandle->rowsFetched && j <= maximum;
j++, row++)
{
thisHandle->rowsUsed++;
if(j > blksize) {
blksize *= 2;
for (i = 0; i < nc; i++)
SET_VECTOR_ELT(data, i,
lengthgets(VECTOR_ELT(data, i), blksize));
}
for (i = 0; i < nc; i++) {
SQLLEN len = thisHandle->ColData[i].IndPtr[row];
switch(thisHandle->ColData[i].DataType) {
case SQL_DOUBLE:
REAL(VECTOR_ELT(data, i))[j-1] =
len == SQL_NULL_DATA ? NA_REAL :
thisHandle->ColData[i].RData[row];
break;
etc...
Googling for SQL_NULL_DATA and related terms finds this page, about the
same issue in a Python driver:
http://code.google.com/p/pyodbc/issues/detail?id=51
It appears as if SQLLEN might be unsigned in 64-bit builds, while
SQL_NULL_DATA is -1. Casting len to be an int rather than an unsigned int
seems to solve the problem for them.
On my machine, /usr/include/sqltypes.h starts like this:
/*
* sqltypes.h
*
* $Id: sqltypes.h,v 1.23 2007/10/07 13:27:13 source Exp $
*
* ODBC typedefs
*
* The iODBC driver manager.
and defines SQLLEN as follows:
#ifdef _WIN64
typedef INT64 SQLLEN;
typedef UINT64 SQLULEN;
typedef UINT64 SQLSETPOSIROW;
#elif defined(STRICT_ODBC_TYPES)
typedef long SQLLEN;
typedef unsigned long SQLULEN;
typedef unsigned short SQLSETPOSIROW;
#else
#define SQLLEN long
#define SQLULEN unsigned long
#define SQLSETPOSIROW unsigned short
#endif
Seems to me like SQLLEN should be signed, but apparently not?
Can anyone help? Thank you!
-Harlan