From 01b5d65a1da80f3cc6120e53bba46e4da2ff44ca Mon Sep 17 00:00:00 2001
From: Tomasz Buchert
Date: Mon, 26 Sep 2011 00:03:47 +0200
Subject: Issue 187: queries are captured and not executed when template panel
 is rendered.

---
 debug_toolbar/utils/tracking/db.py | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

(limited to 'debug_toolbar/utils')

diff --git a/debug_toolbar/utils/tracking/db.py b/debug_toolbar/utils/tracking/db.py
index 7ffacef..1fa7b36 100644
--- a/debug_toolbar/utils/tracking/db.py
+++ b/debug_toolbar/utils/tracking/db.py
@@ -2,6 +2,7 @@ import inspect
 import sys
 
 from datetime import datetime
+from threading import local
 
 from django.conf import settings
 from django.template import Node
@@ -16,7 +17,39 @@ from debug_toolbar.utils.compat.db import connections
 SQL_WARNING_THRESHOLD = getattr(settings, 'DEBUG_TOOLBAR_CONFIG', {}) \
                             .get('SQL_WARNING_THRESHOLD', 500)
 
-class CursorWrapper(object):
+class SQLQueryTriggered(Exception):
+    """Thrown when template panel triggers a query"""
+    pass
+
+class ThreadLocalState(local):
+    def __init__(self):
+        self.enabled = True
+
+    @property
+    def Wrapper(self):
+        return NormalCursorWrapper if self.enabled else ExceptionCursorWrapper
+
+    def recording(self, v):
+        self.enabled = v
+
+state = ThreadLocalState()
+recording = state.recording # export function
+
+def CursorWrapper(*args, **kwds):  # behave like a class
+    return state.Wrapper(*args, **kwds)
+
+class ExceptionCursorWrapper(object):
+    """
+    Wraps a cursor and raises an exception on any operation.
+    Used in Templates panel.
+    """
+    def __init__(self, cursor, db, logger):
+        pass
+
+    def __getattr__(self, attr):
+        raise SQLQueryTriggered()
+
+class NormalCursorWrapper(object):
     """
     Wraps a cursor and logs queries.
     """
@@ -103,4 +136,4 @@ class CursorWrapper(object):
             return getattr(self.cursor, attr)
 
     def __iter__(self):
-        return iter(self.cursor)
\ No newline at end of file
+        return iter(self.cursor)
-- 
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