Scan for tables without relying upon whereclause

Fixed bug where an UPDATE statement against a JOIN using MySQL multi-table
format would fail to include the table prefix for the target table if the
statement had no WHERE clause, as only the WHERE clause were scanned to
detect a "multi table update" at that particular point.  The target
is now also scanned if it's a JOIN to get the leftmost table as the
primary table and the additional entries as additional FROM entries.

Fixes: #5617
Change-Id: I26d74afebe06e28af28acf960258f170a1627823

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/util.py b/lib/sqlalchemy/sql/util.py
index 96fa209fd..e4f7532be 100644
--- a/lib/sqlalchemy/sql/util.py
+++ b/lib/sqlalchemy/sql/util.py
@@ -366,6 +366,19 @@ def clause_is_present(clause, search):
         return False
 
 
+def tables_from_leftmost(clause):
+    if isinstance(clause, Join):
+        for t in tables_from_leftmost(clause.left):
+            yield t
+        for t in tables_from_leftmost(clause.right):
+            yield t
+    elif isinstance(clause, FromGrouping):
+        for t in tables_from_leftmost(clause.element):
+            yield t
+    else:
+        yield clause
+
+
 def surface_selectables(clause):
     stack = [clause]
     while stack: