Re: Deviation from object-relational mapping (pySQLFace)

On okt. 12, 19:54, Paul Boddie <p...@xxxxxxxxxxxxx> wrote:
On 12 Okt, 17:19, sulyokp...@xxxxxxxxx wrote:

I have made a simple python module to handle SQL databases:
https://fedorahosted.org/pySQLFace/wiki
Its goal to separate relational database stuff (SQL) from algorythmic
code (python). A SQLFace is a facade initialized with a configuration
file (XML). It provides callable command objects for each sql query.
The call substitutes template variables with its parameters, and
returns the result of the query.
I would like to get some opinions on this approach.

Not being a fan of object-relational mappers myself, I think that it's
worthwhile to explore other avenues that make database access more
convenient than plain DB-API usage, yet to still expose the benefits
of the database technology. I think that focusing on queries and
operations is the right thing to do, rather than to place the database
schema in a central position like most object-relational mappers do,
and I think that you've made the right decision in preserving the
queries instead of trying to erase all traces of SQL, but I'm not too
convinced by the usage of XML: what I've done myself in various
applications is to define query classes which declare the outputs from
each query as a list stored in a class attribute - something like
this:

class WeatherQuery(Query):

  outputs = ["city", "temp_lo", "temp_hi", "prcp", "date"]
  query = "SELECT city,temp_lo,temp_hi,prcp,date FROM weather"

Naturally, the superclass provides support for the actual query
execution, production of different output representations (such as
XML), and so on. If I wanted to make this more automatic (to stop
people squealing about "DRY" and the repetition of the column names,
although the outputs need not have the same names as the columns), I'd
probably want to parse the SQL (within reason, of course, since SQL is
quite a big language once you start to consider all the different
features).

Still, I don't think there's much to choose between what you've done
and what I've described above, and I think that there's definitely
merit in your approach.

Paul

It is not convincing to look at an XML file alone. Let me give you an
example. Glade is a GTK+ application for creating GTK+ GUI. It
generates an XML file, that can be loaded in every programming
language that has libglade binding. Similarly, there could be a
database design tool to create a database, and save SQL/DML
expressions into an XML config file. Then you create the RDB command
objects by loading the XML in your favourite language. I think
programming languages are intended for describing neither relational
databases nor GUIs.
.

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