Re: [GENERAL] Aquameta 0.1 - Request for reviews, contributors

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
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