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 <n...@cryptonector.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 > -- >
