Re: Aquameta 0.1 - Request for reviews, contributors

Thanks Nico. I definitely like this syntax better.

--
Eric Hanson
CEO, Aquameta Labs
503-929-1073
www.aquameta.com

On Fri, Sep 8, 2017 at 4:26 PM, Nico Williams <nico(at)cryptonector(dot)com> wrote:

>
> Here's a review comment. Just one for now.
>
> Looking at the meta module, I see things like this:
>
> execute 'select (count(*) = 1) from ' || quote_ident((row_id::meta.schema_id).name)
> || '.' || quote_ident((row_id::meta.relation_id).name) ||
> ' where ' || quote_ident((row_id.pk_column_id).name) || '
> = ' || quote_literal(row_id.pk_value)
> into answer;
>
> I recently learned what I find to be a better idiom:
>
> execute format(
> $q$
> select exists (select *
> from %1$I.%2$I
> where %3$I = %4$L);
> $q$,
> -- interpolated arguments here
> (row_id::meta.schema_id).name, (row_id::meta.relation_id).name,
> (row_id.pk_column_id).name, row_id.pk_value
> into answer;
>
> That is, PostgreSQL has extended string literal syntax where you can use
> $stuff$ instead of single-quotes, and that makes it much easier to write
> dynamic (generated for EXECUTE) SQL. In particular, because your
> $EDITOR [generally] won't recognize this, syntax highlighting for the
> $quoted$ code will work as expected!
>
> This is better not only because it's more concise, easier to line-wrap,
> and easier on the eyes, but also because you get to use format(). I
> suspect using format() makes it harder to forget to quote something
> appropriately -- harder to accidentally create a SQL injection
> vulnerability. I usually use argument numbering (%<n>$I) instead of
> referring to the positionally (%I, %L, %s) because it helps a lot
> whenever I need to refer to one of them multiple times.
>
> Of course, this is just a matter of style, but I strongly feel that this
> is the superior style (at least I find or stumble into a better style),
> especially when you have several layers of trigger functions creating
> more trigger functions, as you can easily nest $foo$-quoted string
> literals by having different quote forms for each level.
>
> Also, I used exists() instead of count(*) = 1 -- that's just my personal
> preference, and a less defensible style matter (it is more verbose...).
>
> Nico
> --
>