Hi Lance,
On Wed, 28 Jul 2010 06:45:30 -0500, Lance Edgar <lance.ed...@gmail.com> wrote:
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> On Wed, 2010-07-28 at 11:33 +0000, Faheem Mitha wrote:
>
>> On Wed, 28 Jul 2010 15:17:09 +0530 (IST), Faheem Mitha
>> <fah...@email.unc.edu> wrote:
>> >
>> > Hi,
>>
>> > When calling create_all on a metadata instance after a session has
>> > alrady been opened causes the create_all to hang, I assume because
>> > the session is blocking the create_all. Is there some way to get
>> > create_all to use the existing session, or any other graceful way
>> > around this? Thanks.
>>
>> > I guess another option is to close and then reopen the session after
>> > the create_all has been called, but I'd prefer not to do that if
>> > possible.
>>
>> Puting a session.close() before the create_all fixes the problem. I
>> assume this means that create_all doesn't work in the middle of a
>> transaction, or something like that?
>
>
> I can't speak to the underlying mechanics of create_all(), but calling
> session.close() prior to create_all() would work, as you say. Another
> option would be to simply not use a session, but instead just a
> *connection*. Sessions are specific to the ORM which, according to the
> code you posted, you are not using. So if you really just need to make
> a SELECT call to a table, then instead of creating a session and
> calling .execute() on it, you could instead do this:
> db = create_engine(dbstring)
> meta.bind = db
> db.echo = 'debug'
> make_foo(meta)
> meta.create_all()
> db.connect().execute("select * from foo;")
> make_bar(meta)
> meta.create_all()
The example was just an example. After going back and forth a bit,
I've finally standardized on session as the thing to more around in my
application. The db.connect thing works, I think, because autocommit
is the default for connect.
I'd like to hear an explanation of why create_all is blocked here. I
periodically have my scripts hang for no apparent reason, almost
always because the db is blocking something, so would like to become
more educated on this issue.
Regards, Faheem
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