Re: :PgSQL: More Queestions

On Wednesday, November 20, 2002, at 06:53 AM, Tim Bunce wrote:

>> But if I change it (as I'm seriously considering, in light of
>> PostgreSQL 7.3's support for prepared statements), I'll probably do no
>> parsing for comments.
>
> I think that would be a bad move.

Yes, your last post makes very clear why. Thanks.

> If it's seen the start of a string ("..." or '...') then it just
> keeps copying the string till it finds the same type of quote
> character to mark the end of the string. The 'fiddly bit in the
> middle' is handling backslashes used to escape quote chars in the
> middle of the string: "...\"..." and "...\\" (odd vs even number).

Seems rather opaque. Maybe I'm just reflecting my C-newbieness, but why
wouldn't this work as well? Borrowing a bit from DBD::ODBC here (but
allowing for both kinds of escaping of the quote characters):

if (*src == '"' || *src == '\'') {
if (!in_literal) {
literal_ch = *src;
in_literal = 1;
} else {
if (*src == literal_ch && *(src-1) != '//'
&& *(src-1) != literal_ch) {
in_literal = 0;
}
}
}

> ANSI standard doesn't use backslashes, it uses doubling: "...""..."

Yeah, as Rudy pointed out, however, PostgreSQL uses backslashes as well
as doubling.

> Take a look at dbd_preparse in DBD::Oracle.

Will do, when I'm more awake again and find the tuits...

> There's also a preparse() in DBI.xs which was destined to become a
> standard service offered to drivers - but isn't quite ready yet.

Hrm, yes, that could be quite handy, since dbd_preparse() seems to be
one of the more complex driver functions...

Regards,

David

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