I went though the exact same process of discovery that you did Jonathan :)
It does work perfectly but does not get rendered properly when printing out
the queries (possibly even when I set echo=True on the connection, if I
remember correctly)
On Sun, Sep 22, 2013 at 5:44 PM, Jonathan Vanasco <jonat...@findmeon.com>wrote:
> ah ha! yes!
>
> that is right.
>
> query = select( (these,columns,) ).distinct( this.column )
>
> this was an even tricker problem... and I might have been executing
> correct queries last night without realizing it.
>
> i just noticed that i was getting a correct query in my database, while I
> was seeing the wrong query on screen.
>
> sqlalchemy didn't know that that 'core' commands I was using were for
> postgresql, so it rendered the query not using that dialect.
>
> when i actually did query the database, it was compiling with the right
> dialect :
>
> _query_EXT = dbSession.query( model.Table.data )
> _query_INT = dbSession.query( model.Table.data )
> _slurped = sqlalchemy.union( _query_EXT , _query_INT )
> _slurped = sqlalchemy.sql.expression.alias( _slurped , name='slurped')
> _deduped = sqlalchemy.select(\
> (\
> _slurped.c.object_id.label('object_id') ,
> _slurped.c.event_timestamp.label('event_timestamp')
> ),
> )\
> .distinct( _slurped.c.object_id )\
> .order_by(\
> _slurped.c.object_id.desc() ,
> _slurped.c.event_timestamp.desc()
> )
> _deduped = sqlalchemy.sql.expression.alias( _deduped , name='deduped')
> _culled = sqlalchemy.select( (_deduped.c.object_id,) )\
> .order_by(\
> _deduped.c.event_timestamp.desc()
> )
> _query = _culled
>
>
> # this executes a "DISTINCT ON ( slurped.object_id ) slurped.object_id
> , event_timestamp"
> yay = dbSession.execute( _query )
>
>
> # this renders a "DISTINCT slurped.object_id , event_timestamp"
> nay = str( _query )
>
>
>
>
>
>
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