Re: :PgSQL: More Queestions

On Wednesday, November 20, 2002, at 08:36 AM, Jeff Urlwin wrote:

> See the other posts. They did a better job of describing it.

Right, thanks.

> I'm not sure what it's really trying to do, either, really...

Heh. Thank God we have Tim Bunce to explain it to use mere mortals. ;-)

>> Maybe it's just too complex, because, looking at DBD::ODBC's
>> dbd_preparse(), the handling of literals in the query seems a good
>> deal
>> more straight-forward (though it doesn't appear to handle '\'' or "\""
>> -- am I reading that right?
>
> Nope, it handles " or '.
>
> if (*src == '"' || *src == '\'') {
> etc...
> }

It doesn't appear to handle "...""...", though, right? Or am I missing
it?

>> Ah, that makes sense. Not sure if it's an issue for PostgreSQL, but I
>> doesn't appear to be much of an overhead to set it on a per-execute
>> basis...
>
> Actually, if you can get away with doing it only once, the first
> execute, go
> with it. DBD::ODBC tries to do that, but rechecks under two
> conditions:
> 1) we "know" there are multiple result sets in this query via already
> experiencing it
> 2) the user sets a DBD::ODBC private attributed to recheck the result
> set
> types (this is to support nasty things like stored procedures
> returning only
> one result set per call, but a different result set based upon the
> input
> (yes, I've seen this!).

Bleh!

> My advice: if you don't have to support multiple result sets, do it
once per
> execute. If you setup that "flag" to avoid re-doing work and find
> that you
> need to support multiple-result sets, you can always clear the flag...

I'll have to check with the PostgreSQL folks on this.

PostgreSQL folks, can the same statement return a different number of
fields on different executes? I'm guessing yes for something like this,
though:

CREATE TABLE foo ( bar int, bat, text);

SELECT * FROM foo; -- Returns two fields.

ALTER TABLE foo ADD COLUMN fat int;

SELECT * FROM foo; -- Returns three fields.

> I would make the statement that DBD::Oracle may provide a better
> reference
> on the pre-parse stuff. DBD::ODBC's is probably a bit watered down
> from
> DBD::Oracle -- especially because I'm avoiding comments.

Yep, thanks, I'll check it out.

Regards,

David

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