1.6.1dev: use sorted() instead of ORDER BY session.sid in order t…

…o avoid filesort caused by indexing only a prefix of column values on MySQL (closes #13634) git-svn-id: http://trac.edgewall.org/intertrac/log:/branches/1.6-stable@17760 af82e41b-90c4-0310-8c96-b1721e28e2e2
edgewall · Dec 16, 2023 · a62e8b0 · a62e8b0
1 parent 0c96c81
commit a62e8b0
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Showing 2 changed files with 12 additions and 6 deletions.
diff --git a/trac/env.py b/trac/env.py
@@ -715,15 +715,18 @@ def get_known_users(self, as_dict=False):
 
     @cached
     def _known_users(self):
-        return self.db_query("""
-                SELECT DISTINCT s.sid, n.value, e.value
+        # Use sorted() instead of "ORDER BY s.sid" in order to avoid filesort
+        # caused by indexing only a prefix of column values on MySQL.
+        users = self.db_query("""
+                SELECT s.sid, n.value, e.value
                 FROM session AS s
                  LEFT JOIN session_attribute AS n ON (n.sid=s.sid
                   AND n.authenticated=1 AND n.name = 'name')
                  LEFT JOIN session_attribute AS e ON (e.sid=s.sid
                   AND e.authenticated=1 AND e.name = 'email')
-                WHERE s.authenticated=1 ORDER BY s.sid
+                WHERE s.authenticated=1
         """)
+        return sorted(users, key=lambda u: u[0])
 
     @cached
     def _known_users_dict(self):

diff --git a/trac/web/session.py b/trac/web/session.py
@@ -463,9 +463,12 @@ def _get_list(self, sids):
         sids = {self._split_sid(sid)
                 for sid in sids
                 if sid not in ('anonymous', 'authenticated', '*')}
+        # Use sort() instead of "ORDER BY s.sid, s.authenticated" in order to
+        # avoid filesort caused by indexing only a prefix of column values on
+        # MySQL.
         rows = self.env.db_query("""
-            SELECT DISTINCT s.sid, s.authenticated, s.last_visit,
-                            n.value, e.value, h.value
+            SELECT s.sid, s.authenticated, s.last_visit, n.value, e.value,
+                   h.value
             FROM session AS s
               LEFT JOIN session_attribute AS n
                 ON (n.sid=s.sid AND n.authenticated=s.authenticated
@@ -476,8 +479,8 @@ def _get_list(self, sids):
               LEFT JOIN session_attribute AS h
                 ON (h.sid=s.sid AND h.authenticated=s.authenticated
                     AND h.name='default_handler')
-            ORDER BY s.sid, s.authenticated
             """)
+        rows.sort(key=lambda u: (u[0], u[1]))
         for sid, authenticated, last_visit, name, email, handler in rows:
             if all_anon and not authenticated or all_auth and authenticated \
                     or (sid, authenticated) in sids: