Re: Re: how to get current database connection associated with current thread

> On Aug 24, 2016, at 09:11, Sanjay Rao <[email protected]> wrote:
> 
> I got my answer
> obj._p_jar is connection

If `obj` is a persistent object that has previously been added to or loaded from a Connection, yes, its _p_jar will be a Connection object. 

Note, however, that that connection is not necessarily safe to use or associated with the current thread. If you have a bug in your code that allows a persistent object to leak between threads or outlive a transaction boundary when the connection is closed, you can run into trouble. A faulty cache, for example, can produce this situation, leaving you with ConnectionStateErrors:

py>> import ZODB, ZODB.DemoStorage, persistent, transaction
py>> db = ZODB.DB(ZODB.DemoStorage.DemoStorage())
py>> conn = db.open()
py>> plist = persistent.list.PersistentList()
py>> conn.root()['key'] = plist
# Note that there is no connection yet
py>> plist._p_jar 
# After commit we have a connection
py>> transaction.commit()
py>> plist._p_jar
<Connection at 10728bf30>
# But we still have it after the connection is closed
py>> conn.close()
py>> plist._p_jar
<Connection at 10728bf30>
# And it is useless
py>> plist.thing
Traceback (most recent call last):
  ...
ConnectionStateError: Shouldn't load state for persistent.list.PersistentList 0x316490b7e11981b6 when the connection is closed
py>> plist._p_jar.root()
Traceback (most recent call last):
  ...
ConnectionStateError: The database connection is closed

So I guess I'm just saying, be careful about the lifetime of your persistent objects.

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