Date: Thu, 21 Nov 2002 10:53:32 +0000
From: Adam Witney <awitney@sghms.ac.uk>
In-reply-to: <289E1136-FC56-11D6-8F04-0003931A964A@wheeler.net>
To: David Wheeler <david@wheeler.net>
Cc: dbi-dev@perl.org,
	pgsql-interfaces <pgsql-interfaces@postgresql.org>
Message-id: <BA026BAC.BF01%a.witney@sghms.ac.uk>
MIME-version: 1.0
User-Agent: Microsoft-Entourage/10.1.0.2006
Subject: Re: :PgSQL: More Queestions
Content-type: text/plain; charset=US-ASCII
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> I understand that the goal is to convert the placeholders from '?' or
> ':nn' to the PostgreSQL internal version (':pn'). What I'm referring to
> specifically, however, is this snippet from DBD::Pg:
> 
>        if (in_literal) {
>            /* Check if literal ends but keep quotes in literal */
>            if (*src == in_literal) {
>                int bs = 0;
>                char *str;
>                str = src-1; /* Back a character. */
>                while (*(str - bs) == '\\')
>                    bs++;
>                if (!(bs & 1))
>                    /* bs is an even number? */
>                    in_literal = 0;
>            }
>            *dest++ = *src++;
>            continue;
>        }
> 
> in_literal is set when the last character wasn't a placeholder
> character ('?' or ':') and is either a single or a double quotation
> mark. So while I understand that one might want to ignore placeholder
> characters, I don't really understand what the above code is doing.
> Probably'll be easier for me after I've been looking a C for a while...

One thing you may want to keep in mind is the situation concerning array
slices

If you send a statement like this

my $sth = $dbh->prepare("select cube[1:2][1][1] from test4");

Then the :2 gets treated as a placeholder and gets substituted. From the
trace

dbd_st_execute: statement = >select cube[1NULL][1][1] from test4<
ERROR:  parser: parse error at or near "NULL" at character 14 error 7
recorded: ERROR:  parser: parse error at or near "
NULL" at character 14

As no parameters have been bound to the placeholder then a NULL is
substituted and so it fails.

Or maybe I was doing it wrong and there is a way to get around this already?

Thanks

adam


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