On Mar 22, 2011, at 3:56 PM, Jay Pipes wrote:
> On Tue, Mar 22, 2011 at 3:12 PM, Michael Bayer <mike...@zzzcomputing.com>
> wrote:
>> if you say this:
>>
>> Table('sometable', MetaData(), autoload=True, autoload_with=some_engine)
>>
>> its not looking for "changes", its reflecting the entire form of that table
>> brand new, each time. This because the MetaData() object is empty. If OTOH
>> you were to call the"Table()" constructor multiple times with the same table
>> name and the *same* MetaData object, nothing happens on the second try - the
>> existing Table is used. The example code you had seems to be doing the
>> former, reflecting each time on MetaData(). So it is calling "PRAGMA
>> table_info(tablename)" each time.
>>
>> As far as why it fails in your specific case, I couldn't say for sure, but
>> it seems possible that Migrate's practice of dropping the whole table,
>> copying to a temp table, then copying back to the original table may be part
>> of the problem. Perhaps the pysqlite or sqlite3 does not see the proper
>> state when PRAGMA table_info() is used. Turning on echo='debug' would
>> illustrate the full SQL conversation occurring with the SQLite database.
>
> The test case executes the command `sqlite3
> glance_test_migration.sqlite ".schema images"` directly after doing:
>
> images_table = Table('images', MetaData(), autoload=True,
> autoload_with=self.engine)
>
> As you can see from the output of the test case, the images_table.c
> contains different columns than what is output by the sqlite3 command.
> That is why I think it's an SA problem and nothing to do with the
> migrate script.
Running with "sqlite3" executes a brand new process with all new state, whereas
using "engine" uses a SQLite connection that has remained established
throughout the entire conversation.
Did you run with echo='debug' yet ?
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