[DB-SIG] db module wrapper

Marc Colosimo mcolosimo at mitre.org
Thu Aug 19 15:22:07 CEST 2004

On Aug 18, 2004, at 8:04 PM, Ian Bicking wrote:

> Randall Smith wrote:
>> I have created a db module wrapper for hiding the differences between 
>> the DB API 2 implementations.  I currently testing it on psycopg and 
>> cx_Oracle.  Some of the things I have done are:
>> * Standardize time objects to use Python datetime.datetime and 
>> datetime.date classes for both input and output.  The module converts 
>> between types transparently.  This is working on both psycopg and 
>> cx_Oracle.
> That sounds like a good idea.  It would be important that you can also 
> make it uniformly use mxDateTime or Zope's DateTime, as there are many 
> legacy applications that expect those.  And I think there are some 
> advantages of mxDateTime over datetime, though I don't know what they 
> are.
> It would be nice to have a more extendable way to decode and encode 
> types.  Psycopg has this, but there's no standard.
>> * Standardize the params input to use the ? operator and a list.  The 
>> module translates input params and query into the one appropriate for 
>> the  native module.  For example with cx_Oracle: "Select foo from 
>> table where goo > ?" with params [myparam] converts to "Select foo 
>> from table where goo > :var1" with params {'var1':myparam}.  This is 
>> working with both psycopg and cx_Oracle.
> Does this work with all the cases?  This can be hard, especially the 
> (Postgres) cases:
> SELECT * FROM questions WHERE answer = 'maybe?' AND user_id = ?
> SELECT * FROM questions WHERE answer = '''maybe?''' AND user_id = ?
> SELECT * FROM questions WHERE answer = '\'maybe?\'' AND user_id = ?
> SELECT * FROM questions WHERE answer = '
> maybe
> ?
> ' AND user_id = ?
> SELECT * FROM "questions?" WHERE answer = 'maybe' AND user_id = ?
> For MySQL support, you'd need to recognize double quotes in addition 
> to single quotes, with the backquote for quoted columns.

I would like to make the suggestion of adding something like 
quoteparams (the name in pgdb) to the DB API 3 spec. I have a hack 
which I use this directly to quote params when I write them out to a 
file to be loaded in later. By exporting this, the above wrapper can 
call that and, hopefully, get the correct result back no mater what the 
DB is.


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