Re: Suggesting a libpq addition

From: Andrew Chernow <ac(at)esilo(dot)com>
To: Marc Balmer <marc(at)msys(dot)ch>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Suggesting a libpq addition
Date: 2010-12-06 15:33:02
Message-ID: 4CFD022E.5060406@esilo.com
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>
> That would be a *HUGE* piece of software compared the relatively small
> thing I am suggesting...
>

Sometimes complex and large solutions are required for the simplest of
ideas. I believe this is one of those cases. You can't solve the
"printf style PQexec" properly by merely implementing a sprintf wrapper.

> As for escaping (or not escaping) of string arguments, that can be seen
> as a bug or a feature. I do not wan't automatic escaping of string
> arguments in all cases, e.g. I might to construct an SQL statement with
> dynamic parts "WHERE xy" or "AND a = b".
>
> hypothetical example:
>
> filter = "WHERE name like 'Balmer%'";
> if (sort == SORT_DESC)
> sort = " ORDER BY name DESCENDING";
>
> PQvexec(conn, "SELECT name, nr, id FROM address %s%s", filter, sort);
>
> So what I am aiming at right now is a PQvexec() function that basically
> has printf() like semantics, but adds an additional token to the format
> string (printf uses %s and %b to produce strings.) I am thinking of
> adding %S and %B, which produce strings that are escaped.
>

This suffers from becoming cryptic over time, see Tom Lane's comments
back in 2007 on this
(http://archives.postgresql.org/pgsql-hackers/2007-12/msg00362.php).
libpqtypes uses the human readable %schema.typename (schema is optional)
to specify format specifiers. There is no learning curve or ambiguity,
if you want a point than use "%point", or "%my_type".... libpqtypes
allows you to register aliases (PQregisterSubClasses) so that you can
map %text to %s to make it feel more like C..

--
Andrew Chernow
eSilo, LLC
every bit counts
http://www.esilo.com/

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