Add sql generators to LinearRegression and Ridge.

metrics.py

@@ -699,7 +699,7 @@ def compute_on_sql_sql_mode(self, table, split_by=None, execute=None):
         finally:
           sql.TEMP_TABLE_SUPPORTED = None
     res = execute(str(query))
-    extra_idx = list(utils.get_extra_idx(self, return_superset=True))
+    extra_idx = list(self.get_extra_idx(return_superset=True))
     indexes = split_by + extra_idx if split_by else extra_idx
     columns = [a.alias_raw for a in query.groupby.add(query.columns)]
     columns[:len(indexes)] = indexes
@@ -745,7 +745,7 @@ def to_sql(
     """
     global_filter = utils.get_global_filter(self)
     indexes = sql.Columns(split_by).add(
-        utils.get_extra_idx(self, return_superset=True)
+        self.get_extra_idx(return_superset=True)
     )
     with_data = sql.Datasources()
     if isinstance(table, sql.Sql) and table.with_data:
@@ -1005,6 +1005,32 @@ def add_edges(metric):
     add_edges(self)
     return dot.to_string()
 
+  def get_extra_idx(self, return_superset=False):
+    """Collects the extra indexes added by self and its descendants.
+
+    Args:
+      return_superset: If to return the superset of extra indexes if metric has
+        incompatible indexes.
+
+    Returns:
+      A tuple of column names which are just the index of metric.compute_on(df).
+    """
+    extra_idx = self.extra_index[:]
+    children_idx = [
+        c.get_extra_idx(return_superset)
+        for c in self.children
+        if utils.is_metric(c)
+    ]
+    if len(set(children_idx)) > 1:
+      if not return_superset:
+        raise ValueError('Incompatible indexes!')
+      children_idx_superset = set()
+      children_idx_superset.update(*children_idx)
+      children_idx = [list(children_idx_superset)]
+    if children_idx:
+      extra_idx += list(children_idx[0])
+    return tuple(extra_idx)
+
   def traverse(self, include_self=True, include_constants=False):
     ms = [self] if include_self else list(self.children)
     while ms:
@@ -1358,7 +1384,7 @@ def get_sql_and_with_clause(self, table, split_by, global_filter, indexes,
       The global with_data which holds all datasources we need in the WITH
         clause.
     """
-    utils.get_extra_idx(self)  # Check if indexes are compatible.
+    self.get_extra_idx()  # Check if indexes are compatible.
     local_filter = (
         sql.Filters(self.where_).add(local_filter).remove(global_filter)
     )