Include UPDATE/DELETE extra_froms in correlation

Fixed bug where the multi-table support for UPDATE and DELETE statements
did not consider the additional FROM elements as targets for correlation,
when a correlated SELECT were also combined with the statement.  This
change now includes that a SELECT statement in the WHERE clause for such a
statement will try to auto-correlate back to these additional tables in the
parent UPDATE/DELETE or unconditionally correlate if
:meth:`.Select.correlate` is used.  Note that auto-correlation raises an
error if the SELECT statement would have no FROM clauses as a result, which
can now occur if the parent UPDATE/DELETE specifies the same tables in its
additional set of tables ; specify :meth:`.Select.correlate` explicitly to
resolve.

Change-Id: Ie11eaad7e49af3f59df11691b104d6359341bdae
Fixes: #4313
(cherry picked from commit abeea1d82db34232bbef01e98fa4d1de0f583eb6)

1 files changed, 15 insertions, 12 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 75827b34e..80df2fcb5 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -2177,11 +2177,6 @@ class SQLCompiler(Compiled):
     def visit_update(self, update_stmt, asfrom=False, **kw):
         toplevel = not self.stack
 
-        self.stack.append(
-            {'correlate_froms': {update_stmt.table},
-             "asfrom_froms": {update_stmt.table},
-             "selectable": update_stmt})
-
         extra_froms = update_stmt._extra_froms
         is_multitable = bool(extra_froms)
 
@@ -2191,8 +2186,15 @@ class SQLCompiler(Compiled):
             render_extra_froms = [
                 f for f in extra_froms if f not in main_froms
             ]
+            correlate_froms = main_froms.union(extra_froms)
         else:
             render_extra_froms = []
+            correlate_froms = {update_stmt.table}
+
+        self.stack.append(
+            {'correlate_froms': correlate_froms,
+             "asfrom_froms": correlate_froms,
+             "selectable": update_stmt})
 
         text = "UPDATE "
 
@@ -2286,14 +2288,15 @@ class SQLCompiler(Compiled):
     def visit_delete(self, delete_stmt, asfrom=False, **kw):
         toplevel = not self.stack
 
-        self.stack.append({'correlate_froms': {delete_stmt.table},
-                           "asfrom_froms": {delete_stmt.table},
-                           "selectable": delete_stmt})
-
         crud._setup_crud_params(self, delete_stmt, crud.ISDELETE, **kw)
 
         extra_froms = delete_stmt._extra_froms
 
+        correlate_froms = {delete_stmt.table}.union(extra_froms)
+        self.stack.append({'correlate_froms': correlate_froms,
+                           "asfrom_froms": correlate_froms,
+                           "selectable": delete_stmt})
+
         text = "DELETE "
 
         if delete_stmt._prefixes:
@@ -2398,9 +2401,9 @@ class StrSQLCompiler(SQLCompiler):
             for t in extra_froms)
 
     def delete_extra_from_clause(self, update_stmt,
-                           from_table, extra_froms,
-                           from_hints,
-                           **kw):
+                                 from_table, extra_froms,
+                                 from_hints,
+                                 **kw):
         return ', ' + ', '.join(
             t._compiler_dispatch(self, asfrom=True,
                                  fromhints=from_hints, **kw)