Re: Using the dollar sign as a prefix for named parameter of prepared statement.

2017-08-27 18:13 GMT+03:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> Dmitry Igrishin <dmitigr(at)gmail(dot)com> writes:
> > I'm working on finishing beta release of my C++ API for PostgreSQL. The
> > library
> > have simple SQL parser (preprocessor) to support the queries like that:
>
> > SELECT :"column", $tag$constant string$tag$
> > FROM :tables
> > WHERE name LIKE :'name' AND
> > sex = $1 AND
> > age > $age
>
> > where:
> > :"column" is a variable which will be quoted as identifier (like in
> > psql),
> > :tables is a variable which will be not be quoted at all (like in
> psql),
> > :'name' is a variable which will be quoted as literal (like in psql),
> > $1 is a positional parameter,
> > $age is a named parameter
>
> > Is there are any contraindications/caveats/gotchas on using the dollar
> sign
> > as a prefix for the named parameters?
>
> How are you going to distinguish named parameters from dollar-quote tags?
>

Well, since "The tag, if any, of a dollar-quoted string follows the same
rules as an unquoted identifier ... ",
dollar-quote tags cannot contain spaces, right? This fact can be used to
distingush
named parameters from dollar-quote tags.
If so, the only problem I see here is legalisation of spaces in the tags in
future releases, for example:
select $foo bar$stuff$foo bar$;

>
> I think you're going to end up with weird corner case behaviors if
> you try to squeeze still another meaning into "$letters..."
>
But yes, probably it is better to use another syntax for named parameters.
How about ":_parameter_"?
(Looks not so nice as "$parameter", but compatible with psql and can be
used as easy query testing.)

Thanks!