[DB-SIG] db module wrapper
randall at tnr.cc
Fri Aug 20 20:32:49 CEST 2004
What about executemany? Then you'll have to pass in a list of lists as
l1 = ['harry', 'sam', 'charley']
l2 = [1, 2, 3]
query = "select * from tname where col1 = ", l1, " and col2 = ", l2
Is this what you're talking about? It's actually pretty cool, but a big
break from API 2. Maybe it could be an added feature b/c I want the
wrapper to be DBAPI2 compliant. It wouldn't be that hard to code. The
more I think about it, the more I like it. This is probably what would
happen in practice.
query = 
query.append('select * from tname where col1 = ')
query.append('and col2 = ')
That's actually quite readable. Am I getting the right idea? Is this
what you are intending?
Is this in anyway disadvantageous to the API2 way?
You're certainly on track about the API 3.0 issue. This IS a new API.
The wrapper is implementing a more strict API than 2.0 does.
I'm definitely giving this some thought. It seems very nice.
Vernon Cole wrote:
> I confess, and beg pardon. I let myself wander off from Randall's topic --
> which is creation of a wrapper for various DB API 2.0 packages -- onto the
> topic of creation of DB API 3.0. Nevertheless, I think that Randall's work
> may help to define 3.0 in some ways.
> I feel very strongly that the eventual 3.0 must be able to run simple to
> medium querys, and simple adds or updates, using a completly standardized
> syntax. When one gets to the more complex stuff -- indexing and triggers
> for example -- standardization is out the window. Way out. I think the goal
> of the wrapper is roughly that, too.
> Having said all that, is it not true that the role of cursor.execute() in
> the wrapper is not to PARSE an SQL statement, but to BUILD one?
> The four ways now used to encode parameters are all based loosly on the
> principle of an fprintf() function in C. A string with some type of escape
> patterns is passed, followed by a list of parameters. I am trying to suggest
> that we can simplify things by using the power of python. We are using a
> language with strongly typed parameters. A module implementor can tell at
> run time the data type of the contents of an arbitrary parameter.
> If the cursor.execute() method accepts an arbitrary parameter list, then we
> have no need of escapes. The application programmer simply breaks his sql
> statement at that point, puts in the python variable he has in mind, and
> then continues the SQL as another string literal. The implementor will
> inject the appropriate escape into the string she is building and prepare
> the paramater for passing as needed by the target SQL engine.
> Am I missing something?
> Why would this not work?
> -----Original Message-----
> From: M.-A. Lemburg [mailto:mal at egenix.com]
> Sent: Friday, August 20, 2004 5:06 AM
> Before yuo head off, may I suggest that you create a layer on
> top of the DB API compatible drivers (much like you have in Perl)
> instead of forcing incompatible changes onto the various DB interface
> modules ?!
> The user can then use the abstraction layer and the module
> authors can continue to craft modules that provide interfaces
> which adhere to the DB API interface standard.
> The typical approach to the problem (if at all) that
> Guido mentions is to have an application specific
> abstraction layer which then gets adapted for the
> intended list of database backends.
> This layer has all the knowledge about the application
> needs as well as the ways in which these needs can be
> mapped to the databases (both in terms of Python database
> module interface and database SQL dialect).
> In my experience trying to generalize these abstraction
> layers always fails at some point: either the database
> SQL dialects and offered features are too different,
> which let's you end up only supporting a very low-tech
> common subset, or the abstraction has to go through
> enormous lengths at trying to create a common behaviour
> among the database backends (eg. on how multiple result
> sets are handled, array processing, result set scrolling,
> DB-SIG maillist - DB-SIG at python.org
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