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<p class=MsoNormal>Hello all,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>“sqlalchemy.exc.OperationalError: (OperationalError)
internal error in 'BEGIN': not all arguments converted during string formatting
'select current_schema()' [None]”.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Obviously, this is not in the PyGreSQL code, so I chased
this error down the stack trace to the method Connection_<i>cursor</i>_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:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>“pg.OperationalError: internal error in 'BEGIN': not
all arguments converted during string formatting”<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>“TypeError: not all arguments converted during string
formatting”<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>if params == [None]:<o:p></o:p></p>
<p class=MsoNormal>
return string<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks in advance,<o:p></o:p></p>
<p class=MsoNormal>Mike<o:p></o:p></p>
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