Re: [gnome-db] Studying the posibility to add parametrized statements

[Rodrigo Moya <rodrigo gnome-db org>]

On Mon, 2004-09-27 at 17:43 +0200, Vivien Malerba wrote:
> On Mon, 27 Sep 2004 11:12:26 +0000, Jeronimo Albi
> <amenofisvii yahoo com ar> wrote:
> > I've been studying the posibility to add parametrized statements to
> > libgda, but the modifications needed are important, so I'd need some
> > advise :-).
> > 
> > These are the steps i thought:
> > 
> > 1. Set gda_command text with the parametrized statement.
> > 2. Somehow, prepare the statement to let the provider get parameters
> >     info (like parameters data type), and construct a list with
> >     "parameter objects".
> > 3. Set parameter values (using some gda_command method).
> > 4. Finally execute gda_command.
> > 
> > This method would need:
> > 
> > 1. gda_command_prepare (), gda_command_get_parameter (),
> >     gda_command_parameter_count (), gda_command_get_parameter_list (),
> >     some execute method form parametrized statements and so no.
> > 2. A new class named sql_parameter, command_parameter, cmd_parameter,
> >     or any other name :-), to manage parameters.
> > 3. A set of functions to let providers process parametrized statements.
> > 4. To add GDA_CONNECTION_FEATURE_PARAMETRIZED_SQL or similar.
> > 
> > Is this right ?
> > 
> > Seems like a lot of work :-D.
> > I would really apreciate any comment.
> > Thanks
> > 
> 
> I've already done this for Mergeant/libmergeant.
> 
> Basically, any SQL statement can have parameters identified by a value
> of ## and parameter specifications between square brackets. For
> example one can write
> SELECT name FROM table WHERE name='joe' [...]
> or 
> SELECT name FROM table WHERE name=## [...]
> the above statement require one parameter for the "name=" condition.
> In the first statament, the default value for the parameter is 'joe'
> and in the second example, there is no default value for the
> parameter.
> 
> The para specifications between the square brackets are:
> :name="my para name"
> :descr="my para description"
> :type="the DBMS type"
> :nullok="TRUE"
> :isparam="FALSE" (default=TRUE)
> 
> so the above example can be:
> SELECT name FROM table WHERE name='joe' [:name="User name"
> :descr="Enter the user name to look for" :type="varchar"]
> 
> The SQL parser in libgda (libsql/*) already supports this syntax.
> 
> Libmergeant also has a small parser to isolate the parameters from any
> text (usefull when the SQL text can't be parsed by libgda's parser for
> various reasons); it's in libmergeant/parser/*
> 
> I think it would be a good idea to start libgda's implementation of
> parameters with the same syntax and the same libgda's parser.
> 
even better, how much code can be got from libmergeant and be integrated
into libgda? I guess that would save us a lot of work.

Again, I think any extension of this kind you do to libmergeant makes a
lot of sense in libgda/libgnomedb, so I think it would be much better if
you could comment on the new features you add to libmergeant before
doing so, so that we can decide how it would fit better into
libgda/libgnomedb.

As you know, I really want to get libmergeant merged with
libgda/libgnomedb in the shorter possible time, so any step we do now in
that direction will save us a lot of time.
-- 
Rodrigo Moya <rodrigo gnome-db org>