From 9e1447f6ff34be5d994548d8a266c473e7a2a638 Mon Sep 17 00:00:00 2001
From: Bertrand Bordage <bordage.bertrand@gmail.com>
Date: Wed, 18 Feb 2015 00:32:51 +0100
Subject: [PATCH] Handles rare complex queries.

---
 cachalot/utils.py | 43 ++++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/cachalot/utils.py b/cachalot/utils.py
index 59b8b8a..c1c7ee0 100644
--- a/cachalot/utils.py
+++ b/cachalot/utils.py
@@ -6,7 +6,7 @@ from time import time
 
 import django
 from django.db import connections
-from django.db.models.sql.where import ExtraWhere
+from django.db.models.sql.where import ExtraWhere, SubqueryConstraint
 if django.VERSION[:2] >= (1, 7):
     from django.utils.module_loading import import_string
 else:
@@ -75,6 +75,32 @@ def _get_tables_from_sql(connection, lowercased_sql):
             if t in lowercased_sql]
 
 
+def _find_subqueries(children):
+    for child in children:
+        if isinstance(child, SubqueryConstraint):
+            yield child.query_object.query
+        elif isinstance(child, tuple) and hasattr(child[-1], 'query'):
+            yield child[-1].query
+        if hasattr(child, 'children'):
+            for grand_child in _find_subqueries(child.children):
+                yield grand_child
+
+
+def _get_tables(query, db_alias):
+    tables = set(query.table_map)
+    tables.add(query.model._meta.db_table)
+    subquery_constraints = _find_subqueries(query.where.children
+                                            + query.having.children)
+    for subquery in subquery_constraints:
+        tables.update(_get_tables(subquery, db_alias))
+    if query.extra_select or hasattr(query, 'subquery') \
+            or any(isinstance(c, ExtraWhere) for c in query.where.children):
+        sql = query.get_compiler(db_alias).as_sql()[0].lower()
+        additional_tables = _get_tables_from_sql(connections[db_alias], sql)
+        tables.update(additional_tables)
+    return tables
+
+
 def _get_table_cache_keys(compiler):
     """
     Returns a ``list`` of cache keys for all the SQL tables used
@@ -86,18 +112,9 @@ def _get_table_cache_keys(compiler):
     :rtype: list
     """
 
-    query = compiler.query
-    using = compiler.using
-
-    tables = set(query.table_map)
-    tables.add(query.model._meta.db_table)
-    if query.extra_select or any([isinstance(c, ExtraWhere)
-                                  for c in query.where.children]):
-        sql = compiler.as_sql()[0].lower()
-        connection = connections[using]
-        additional_tables = _get_tables_from_sql(connection, sql)
-        tables.update(additional_tables)
-    return [_get_table_cache_key(using, t) for t in tables]
+    db_alias = compiler.using
+    tables = _get_tables(compiler.query, db_alias)
+    return [_get_table_cache_key(db_alias, t) for t in tables]
 
 
 def _invalidate_table_cache_keys(cache, table_cache_keys):