reuse of a closed cursor

[Christian Boos]

At least with PySqlite, it's not possible to reuse a cursor after a rollback has been performed on the connection it was created from.

2010-01-08 04:57:04,395 Trac[main] ERROR: Internal Server Error:
Traceback (most recent call last):
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/web/main.py", line 450, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/web/main.py", line 229, in dispatch
    req.session.save()
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/web/session.py", line 100, in save
    (self.sid,))
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/db/util.py", line 64, in execute
    return self.cursor.execute(sql_escape_percent(sql), args)
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/db/sqlite_backend.py", line 80, in execute
    result = PyFormatCursor.execute(self, *args)
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/db/sqlite_backend.py", line 59, in execute
    args or [])
  File "/usr/local/virtualenv-0.11/lib/python2.5/site-packages/Trac-0.11.7stable_r8997-py2.5.egg/trac/db/sqlite_backend.py", line 51, in _rollback_on_error
    return function(self, *args, **kwargs)
ProgrammingError: Cannot operate on a closed cursor.

0.12 version of the same error:

2010-03-02 11:10:25,782 Trac[main] ERROR: Internal Server Error:
Traceback (most recent call last):
  File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 499, in _dispatch_request
    dispatcher.dispatch(req)
  File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 255, in dispatch
    req.session.save()
  File "build/bdist.linux-x86_64/egg/trac/web/session.py", line 88, in save
    @with_transaction(self.env)
  File "build/bdist.linux-x86_64/egg/trac/db/util.py", line 36, in transaction_wrapper
    fn(dbtmp)
  File "build/bdist.linux-x86_64/egg/trac/web/session.py", line 108, in delete_session_cookie
    (self.sid,))
  File "build/bdist.linux-x86_64/egg/trac/db/util.py", line 90, in execute
    return self.cursor.execute(sql_escape_percent(sql), args)
  File "build/bdist.linux-x86_64/egg/trac/db/sqlite_backend.py", line 77, in execute
    result = PyFormatCursor.execute(self, *args)
  File "build/bdist.linux-x86_64/egg/trac/db/sqlite_backend.py", line 56, in execute
    args or [])
  File "build/bdist.linux-x86_64/egg/trac/db/sqlite_backend.py", line 48, in _rollback_on_error
    return function(self, *args, **kwargs)
ProgrammingError: Cannot operate on a closed cursor.

As discussed in ticket:9077#comment:4 point 2.

[Christian Boos]

web: avoid using a cursor after the connection from which it depends has been rollbacked

[Christian Boos]

Please test and review the above patch.

For some background on the problem, see also ticket:9077#comment:10.

[Christian Boos]

Or alternatively, we could just return when a concurrent save was detected (#3563), see t9104-fix-operate-closed-cursor-r9282.2.diff​.

[Christian Boos]

alternative solution, returning earlier

[Christian Boos]

First alternative picked for 0.11-stable in r9336, on trunk I'll do the second one.

[Christian Boos]

Ported to trunk in r9342, using the second alternative.

[anonymous]

Looks like the changes that closed #7663 were removed in the changes that fixed this ticket. I noticed this because I now have .12.1 and am getting the "IntegrityError: duplicate key violates unique constraint "session_attribute_pk"" logged in #7663 during Performance Testing. It actually causes the performance testing to stop due to the high volume of errors (repeating the one below). There are plans to log a defect.

Traceback (most recent call last):

File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 511, in _dispatch_request File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 260, in dispatch File "build/bdist.linux-x86_64/egg/trac/web/session.py", line 88, in save File "build/bdist.linux-x86_64/egg/trac/db/api.py", line 77, in transaction_wrapper File "build/bdist.linux-x86_64/egg/trac/web/session.py", line 113, in delete_session_cookie File "build/bdist.linux-x86_64/egg/trac/db/util.py", line 85, in executemany

IntegrityError: duplicate key value violates unique constraint "session_attribute_pk" IntegrityError: duplicate key value violates unique constraint "session_attribute_pk"

[Remy Blank]

The fix has been re-introduced in [10823].