zhaoyongjie commented on a change in pull request #13739:
URL: https://github.com/apache/superset/pull/13739#discussion_r605344811
##########
File path: superset/connectors/sqla/models.py
##########
@@ -882,6 +867,51 @@ def adhoc_metric_to_sqla(
return self.make_sqla_column_compatible(sqla_metric, label)
+ def make_sqla_column_compatible(
+ self, sqla_col: Column, label: Optional[str] = None
+ ) -> Column:
+ """Takes a sqlalchemy column object and adds label info if supported
by engine.
+ :param sqla_col: sqlalchemy column instance
+ :param label: alias/label that column is expected to have
+ :return: either a sql alchemy column or label instance if supported by
engine
+ """
+ label_expected = label or sqla_col.name
+ db_engine_spec = self.database.db_engine_spec
+ # add quotes to tables
+ if db_engine_spec.allows_alias_in_select:
+ label = db_engine_spec.make_label_compatible(label_expected)
+ sqla_col = sqla_col.label(label)
+ return sqla_col
+
+ def make_orderby_compatible(
+ self, select_exprs: List[ColumnElement], orderby_exprs:
List[ColumnElement]
+ ) -> None:
+ """
+ If needed, make sure aliases for selected columns are not used in
+ `ORDER BY`.
+
+ In some databases (e.g. Presto), `ORDER BY` clause is not able to
+ automatically pick the source column if a `SELECT` clause alias is
named
+ the same as a source column. In this case, we update the SELECT alias
to
+ another name to avoid the conflict.
+ """
+ if self.database.db_engine_spec.allows_alias_to_source_column:
Review comment:
I recommend making this change by default.
for instance, this SQL in Postgres. the 'ORDER BY' clause still refer to the
original `score` column. We should try to avoid the same `Column Name` and
`Column Alias`
```
SELECT name, sum(score) as score
FROM (
SELECT 'a' as name, 4 as score
UNION ALL
SELECT 'b', 5
UNION ALL
SELECT 'a', 4
) t
GROUP BY name
ORDER by max(score) desc
```
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