QODBC: fix converted string values empty SQLServer 2012

SQL Server 2012 Native Client (version 11.0.2100.60) or later introduced
a change in the behavior of the SQLGetData method when converted string values
are involved. In older version a (sometimes wrong) size was returned. Now always
SQL_NO_TOTAL is returned which signals to read as much data as available.
SQL_NO_TOTAL was handled like SQL_NULL_DATA in the code before which indicates a
NULL value so the returned string was empty.

See link for more info: http://msdn.microsoft.com/en-us/library/jj219209.aspx

Change-Id: Ia0d2296caf593890b301ee1848d1bf3eb8d7b6fe
Reviewed-by: Mark Brand <mabrand@mabrand.nl>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/sql/drivers/odbc/qsql_odbc.cpp b/src/sql/drivers/odbc/qsql_odbc.cpp
index f95fb8868e..2b14809943 100644
--- a/src/sql/drivers/odbc/qsql_odbc.cpp
+++ b/src/sql/drivers/odbc/qsql_odbc.cpp
@@ -373,10 +373,20 @@ static QString qGetStringData(SQLHANDLE hStmt, int column, int colSize, bool uni
                             colSize*sizeof(SQLTCHAR),
                             &lengthIndicator);
             if (r == SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO) {
-                if (lengthIndicator == SQL_NULL_DATA || lengthIndicator == SQL_NO_TOTAL) {
+                if (lengthIndicator == SQL_NULL_DATA) {
                     fieldVal.clear();
                     break;
                 }
+                // starting with ODBC Native Client 2012, SQL_NO_TOTAL is returned
+                // instead of the length (which sometimes was wrong in older versions)
+                // see link for more info: http://msdn.microsoft.com/en-us/library/jj219209.aspx
+                // if length indicator equals SQL_NO_TOTAL, indicating that
+                // more data can be fetched, but size not known, collect data
+                // and fetch next block
+                if (lengthIndicator == SQL_NO_TOTAL) {
+                    fieldVal += fromSQLTCHAR(buf, colSize);
+                    continue;
+                }
                 // if SQL_SUCCESS_WITH_INFO is returned, indicating that
                 // more data can be fetched, the length indicator does NOT
                 // contain the number of bytes returned - it contains the