Adding upstream version 6.0.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

sqlglot/optimizer/isolate_table_selects.py

@@ -0,0 +1,31 @@
+from sqlglot import alias, exp
+from sqlglot.errors import OptimizeError
+from sqlglot.optimizer.scope import traverse_scope
+
+
+def isolate_table_selects(expression):
+    for scope in traverse_scope(expression):
+        if len(scope.selected_sources) == 1:
+            continue
+
+        for (_, source) in scope.selected_sources.values():
+            if not isinstance(source, exp.Table):
+                continue
+
+            if not isinstance(source.parent, exp.Alias):
+                raise OptimizeError(
+                    "Tables require an alias. Run qualify_tables optimization."
+                )
+
+            parent = source.parent
+
+            parent.replace(
+                exp.select("*")
+                .from_(
+                    alias(source, source.name or parent.alias, table=True),
+                    copy=False,
+                )
+                .subquery(parent.alias, copy=False)
+            )
+
+    return expression