Handle NULLs in ClickHouse !=

Author: igorkramaric

daffodil/clickhouse_query_delegate.pyx

@@ -76,6 +76,8 @@ cdef class ClickHouseQueryDelegate(BaseDaffodilDelegate):
                 return f"{cast_expr} NOT IN {val_expr}"
         else:
             val_expr = self._format_value(val_obj)
+            if op == "!=":
+                return f"({key_expr} != {val_expr}) OR ({key_expr} IS NULL)"
             return f"{key_expr} {op} {val_expr}"
 
     def call(self, predicate, query=None):

test/test_clickhouse.py

@@ -43,6 +43,11 @@ def test_existence_false(self):
         sql = self._render('zip_code ?= false')
         self.assertEqual(sql, "(isNull(hs_data.zip_code))")
 
+    def test_not_equal_with_null(self):
+        fltr = '{\n  "uni_valspar_qx_thanks" ?= true\n  "wave" != "post"\n}'
+        expected = "((isNotNull(hs_data.uni_valspar_qx_thanks)) AND ((hs_data.wave != 'post') OR (hs_data.wave IS NULL)))"
+        self.assertEqual(self._render(fltr), expected)
+
 
 if __name__ == '__main__':
     unittest.main()