[Twisted-Python] Using different cursor types with psycopg+twisted.enterprise.adbapi?

Phil Christensen phil at bubblehouse.org
Fri Apr 18 14:11:46 EDT 2008

On Apr 18, 2008, at 2:05 PM, Phil Christensen wrote:
> On Apr 18, 2008, at 1:09 PM, Nathan wrote:
>> In my non-twisted scripts, I usually use psycopg2 DictCursors so that
>> my query results come back in dicts instead of lists.
>> curs = db.cursor(cursor_factory = psycopg2.extras.DictCursor)
>> Now I'd like to do the same thing in Twisted.  Is there a way to ask
>> t.e.adbapi to use that DictCursor cursor factory?
>> Or maybe there's a way to globally configure psycopg2 so that it used
>> psycopg2.extras.DictCursor by default...
> I think I ran into this while trying to support multiple DB drivers.
> The adbapi.ConnectionPool constructor automatically passes any  
> additional arguments or keyword params to the DB-API Connection  
> object constructor.
> I remember having problems setting a default cursor via Connection()  
> params, but I thought it was with the other PG driver, not psycopg2.  
> In fact, I almost seem to remember pgdb not even directly supporting  
> DictCursors at all, but I could easily be mistaken.
> In any event, I ended up having the real drivers return a the row as  
> sequence (the normal behavior), and made a trivial ConnectionPool  
> subclass that contained the following:
[snip wrong code]
> Hacky, I know, but it did the trick. This way if you have a driver  
> that does support DictCursors by passing params to the Connection  
> constructor, it will use that functionality instead.

Ah yes, this is the right one:

    def _runInteraction(self, interaction, *args, **kw):
        conn = adbapi.Connection(self)
        trans = adbapi.Transaction(self, conn)
            result = interaction(trans, *args, **kw)
            if(result and isinstance(result[0], (list, tuple))):
                colanmes = [c[0] for c in trans._cursor.description]
                result = [dict(zip(colnames, item)) for item in result]
            return result

Small change, but I was feeling some....what's the opposite of shame?  
Pride? No, not that far from shame...less shame?


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