OPTIMIZATION #2: Direct Python C API for integer and floating-point types

- Replaced pybind11 wrappers with direct Python C API calls
- SQL_INTEGER, SQL_SMALLINT, SQL_BIGINT: PyLong_FromLong/PyLong_FromLongLong
- SQL_TINYINT, SQL_BIT: PyLong_FromLong/PyBool_FromLong
- SQL_REAL, SQL_DOUBLE, SQL_FLOAT: PyFloat_FromDouble
- Uses PyList_SET_ITEM macro for direct list assignment (no bounds checking)
- Eliminates pybind11 wrapper overhead for simple numeric types
- Added PERF_TIMER instrumentation for each numeric type conversion

Author: bewithgaurav

mssql_python/pybind/ddbc_bindings.cpp

@@ -3354,23 +3354,58 @@ SQLRETURN FetchBatchData(SQLHSTMT hStmt, ColumnBuffers& buffers, py::list& colum
                     break;
                 }
                 case SQL_INTEGER: {
-                    row[col - 1] = buffers.intBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::int_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyInt = PyLong_FromLong(buffers.intBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyInt);
+                    }
                     break;
                 }
                 case SQL_SMALLINT: {
-                    row[col - 1] = buffers.smallIntBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::smallint_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyInt = PyLong_FromLong(buffers.smallIntBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyInt);
+                    }
                     break;
                 }
                 case SQL_TINYINT: {
-                    row[col - 1] = buffers.charBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::tinyint_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyInt = PyLong_FromLong(buffers.charBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyInt);
+                    }
                     break;
                 }
                 case SQL_BIT: {
-                    row[col - 1] = static_cast<bool>(buffers.charBuffers[col - 1][i]);
+                    PERF_TIMER("construct_rows::bit_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyBool = PyBool_FromLong(buffers.charBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyBool);
+                    }
                     break;
                 }
                 case SQL_REAL: {
-                    row[col - 1] = buffers.realBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::real_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyFloat = PyFloat_FromDouble(buffers.realBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyFloat);
+                    }
                     break;
                 }
                 case SQL_DECIMAL:
@@ -3392,7 +3427,14 @@ SQLRETURN FetchBatchData(SQLHSTMT hStmt, ColumnBuffers& buffers, py::list& colum
                 }
                 case SQL_DOUBLE:
                 case SQL_FLOAT: {
-                    row[col - 1] = buffers.doubleBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::double_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyFloat = PyFloat_FromDouble(buffers.doubleBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyFloat);
+                    }
                     break;
                 }
                 case SQL_TIMESTAMP:
@@ -3405,7 +3447,14 @@ SQLRETURN FetchBatchData(SQLHSTMT hStmt, ColumnBuffers& buffers, py::list& colum
                     break;
                 }
                 case SQL_BIGINT: {
-                    row[col - 1] = buffers.bigIntBuffers[col - 1][i];
+                    PERF_TIMER("construct_rows::bigint_c_api_assign");
+                    if (buffers.indicators[col - 1][i] == SQL_NULL_DATA) {
+                        Py_INCREF(Py_None);
+                        PyList_SET_ITEM(row.ptr(), col - 1, Py_None);
+                    } else {
+                        PyObject* pyInt = PyLong_FromLongLong(buffers.bigIntBuffers[col - 1][i]);
+                        PyList_SET_ITEM(row.ptr(), col - 1, pyInt);
+                    }
                     break;
                 }
                 case SQL_TYPE_DATE: {