FIX: clarify decimal parsing in bulk fetch and add regression test

mssql_python/pybind/ddbc_bindings.cpp

@@ -2899,7 +2899,7 @@ SQLRETURN SQLGetData_wrap(SqlHandlePtr StatementHandle, SQLUSMALLINT colCount, p
     SQLHSTMT hStmt = StatementHandle->get();
 
     // Cache decimal separator to avoid repeated system calls
-    std::string decimalSeparator = GetDecimalSeparator();
+
 
     for (SQLSMALLINT i = 1; i <= colCount; ++i) {
         SQLWCHAR columnName[256];
@@ -3622,7 +3622,7 @@ SQLRETURN FetchBatchData(SQLHSTMT hStmt, ColumnBuffers& buffers, py::list& colum
             columnInfos[col].processedColumnSize + 1;  // +1 for null terminator
     }
 
-    std::string decimalSeparator = GetDecimalSeparator();  // Cache decimal separator
+
 
     // Performance: Build function pointer dispatch table (once per batch)
     // This eliminates the switch statement from the hot loop - 10,000 rows × 10

tests/test_decimal_separator.py

@@ -0,0 +1,59 @@
+import os
+from decimal import Decimal
+
+import pytest
+import mssql_python
+
+
+@pytest.mark.skipif(not os.getenv("DB_CONNECTION_STRING"), reason="Requires DB_CONNECTION_STRING")
+def test_decimal_separator_bug(db_connection):
+    """
+    Test that fetchall() dealing with DECIMALS works correctly even when
+    setDecimalSeparator is set to something other than '.'
+    """
+    conn = db_connection
+    cursor = None
+
+    try:
+        cursor = conn.cursor()
+        # Create a temp table
+        cursor.execute("CREATE TABLE #TestDecimal (Val DECIMAL(10, 2))")
+        cursor.execute("INSERT INTO #TestDecimal VALUES (1234.56)")
+        cursor.execute("INSERT INTO #TestDecimal VALUES (78.90)")
+        conn.commit()
+
+        # Set custom separator
+        mssql_python.setDecimalSeparator(",")
+
+        # Test fetchall
+        cursor.execute("SELECT Val FROM #TestDecimal ORDER BY Val")
+        rows = cursor.fetchall()
+
+        # Verify fetchall results
+        assert len(rows) == 2, f"Expected 2 rows, got {len(rows)}"
+        assert isinstance(rows[0][0], Decimal), f"Expected Decimal, got {type(rows[0][0])}"
+        assert rows[0][0] == Decimal("78.90"), f"Expected 78.90, got {rows[0][0]}"
+        assert rows[1][0] == Decimal("1234.56"), f"Expected 1234.56, got {rows[1][0]}"
+
+        # Verify fetchmany
+        cursor.execute("SELECT Val FROM #TestDecimal ORDER BY Val")
+        batch = cursor.fetchmany(2)
+        assert len(batch) == 2
+        assert batch[1][0] == Decimal("1234.56")
+
+        # Verify fetchone behavior is consistent
+        cursor.execute("SELECT CAST(99.99 AS DECIMAL(10,2))")
+        val = cursor.fetchone()[0]
+        assert isinstance(val, Decimal)
+        assert val == Decimal("99.99")
+
+    finally:
+        # Reset separator to default just in case
+        mssql_python.setDecimalSeparator(".")
+        if cursor:
+            try:
+                cursor.execute("DROP TABLE #TestDecimal")
+                conn.commit()
+            except Exception:
+                pass
+            cursor.close()