[PyGreSQL] PyGreSQL changes to integrate with SQLAlchemy

[Christopher Hilton]

That's awesome news!

I'm in the midst of fleshing out the pgdb.txt file to include documentation for our differences/extensions to DB-ABI v2.0 I've had to suspend the work for a bit (client work calls) but will be back to it as soon as possible.

-- Chris

On Feb 15, 2010, at 12:00 PM, Michael Dominice wrote:

> Hello all,
>  
> I have been attempting to integrate PyGreSQL’s DBAPI compliant module as the database driver for SQLAlchemy.  After initial searching, I found that you can pass the driver as the “module” argument when initializing SQLAlchemy, and that this was the way to get it to start working with PyGreSQL. 
>  
> The only Python PostgreSQL driver that SQLAlchemy “supports” is Psycopg2, but I am unable to use that library due to its license restrictions, and I have been using PyGreSQL for quite some time now, so it’s a much more attractive alternative.
>  
> I had been attempting to write the code using Psycopg2 as the Postgres driver for SQLAlchemy and was able to reflect my schema without hang-ups, but wanted to try using PyGreSQL.  My first attempt at replacing the driver and reflecting my schema resulted in the following error:
>  
> “sqlalchemy.exc.OperationalError: (OperationalError) internal error in 'BEGIN': not all arguments converted during string formatting 'select current_schema()' [None]”.
>  
> Obviously, this is not in the PyGreSQL code, so I chased this error down the stack trace to the method Connection_cursor_execute() method in base.py (SQLAlchemy).  I changed the exception that is caught there to look into exactly what is happening, and then ran my code again, resulting in an error being thrown in PyGreSQL:
>  
> “pg.OperationalError: internal error in 'BEGIN': not all arguments converted during string formatting”
>  
> I chased this error to where it was being raised, which was in lines 290-291 in pgdbCursor.executemany() method in pgdb.py.  I removed the exception handling so I could further find where things were going wrong.  I found that the error in question was:
>  
> “TypeError: not all arguments converted during string formatting”
>  
> This was occurring at line 222 in pgdb.py in the method pgdbCursor._quoteparams().  After some more inspection, I found that the params argument was a list containing only the value None, that is, [None].  I added a check at the beginning of that method for this value:
>  
> if params == [None]:
>                 return string
>  
> After this change, my code functioned exactly the same as when I was working with Psycopg2, and I’ve been running fine for about a month of work.
>  
> My question is whether or not this is something that is OK to change, as I am not familiar with the inner workings of PyGreSQL and wanted to see if there are any repercussions of this change that I could potentially be missing.
>  
> I am using Python 2.5.4, working on Windows XP SP 2,  Using SQLAlchemy 0.5.6 and the latest stable version of PyGreSQL.
>  
> Thanks in advance,
> Mike
> _______________________________________________
> PyGreSQL mailing list
> PyGreSQL at Vex.Net
> http://mailman.vex.net/mailman/listinfo/pygresql

Chris Hilton                       tildeChris -- http://myblog.vindaloo.com
                                        e: -- chris /at/ vindaloo /dot/ com
.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.--.~~.
                        "I'm on the outside looking inside, What do I see?
                              Much confusion, disillusion, all around me."
                                        -- Ian McDonald / Peter Sinfield