handle postgres dialect

great_expectations/expectations/metrics/util.py

@@ -414,17 +414,18 @@ def get_sqlalchemy_column_metadata(  # noqa: C901
             )
 
         dialect_name = execution_engine.dialect.name
-        if dialect_name == GXSqlDialect.SNOWFLAKE:
+        if dialect_name in [GXSqlDialect.POSTGRESQL, GXSqlDialect.SNOWFLAKE]:
             # WARNING: Do not alter columns in place, as they are cached on the inspector
             columns_copy = [column.copy() for column in columns]
             for column in columns_copy:
                 column["type"] = column["type"].compile(dialect=execution_engine.dialect)
-            return [
-                # TODO: SmartColumn should know the dialect and do lookups based on that
-                CaseInsensitiveNameDict(column)
-                for column in columns_copy
-            ]
-
+            if dialect_name == GXSqlDialect.SNOWFLAKE:
+                return [
+                        # TODO: SmartColumn should know the dialect and do lookups based on that
+                        CaseInsensitiveNameDict(column)
+                        for column in columns_copy
+                ]
+            return columns_copy
         return columns
     except AttributeError as e:
         logger.debug(f"Error while introspecting columns: {e!r}", exc_info=e)