[DB-SIG] paramstyles, again

[Carsten Haese]

On Mon, 2007-06-04 at 15:32 +0200, M.-A. Lemburg wrote:
> Do you really think it's reasonable to have the module parse
> every single SQL statement just to detect the param style ?

Well, at least I don't think it's unreasonable to do so. This parsing is
not expensive and only happens when the query is prepared, so the
performance impact is minimal.

> What happens if you're in qmark style mode and the SQL statement
> contains substrings which look like named style (but are not
> intended that way, e.g. think stored procedures) ?

Do you have a concrete example?

> This approach also contradicts the explicit is better than
> implicit Zen rule.

Well, one might argue that the paramstyle is explicitly visible in the
format of the query string.

> Just so that there's no misunderstanding: you're free to implement
> this sort of extension in your module(s), but making this
> mandatory in the spec feels wrong.

Fair enough.

> Following you proposal to require auto-detection, this would mean
> more than just duck-typing. You wouldn't know what type to expect
> until you've parsed the SQL statement string - ie. when you're
> already inside the .execute() method and passed the argument
> parsing step.
> 
> That's a bit much too dynamic and too implicit for an interface
> specification.

I thought being dynamic was Pythonic ;) Anyway, I do think we can reach
a compromise here:

> So I'm:
> 
>  * +1 on making support one param style mandatory for all
>    implementations

Any one? Let's make named mandatory, then.

>  * +1 on requiring an interface to adjust the param style on a
>    per connection or even per cursor basis, so that it's easy
>    to setup an implementation to the mandatory param style
>    (in case the module defaults to another param style for backwards
>    compatibility reasons)
> 
>    This interface would have to support at least the mandatory
>    param style.

+1, let's discuss what that interface should look like.

>  * -1 on doing auto-detection of param styles at .execute()
>    call time based on parsing the SQL statement

I now agree with -1 on making auto-detection mandatory as long as there
is a way to turn it on. How about making a special paramstyle called
auto?

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         Carsten Haese          |  Phone:       (419) 861-3331
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