> On Wed, Dec 09, 2020 at 04:59:34PM -0500, Tom Lane wrote: > > 0001 adds the ability to attach a subscript handler to an existing > data type with ALTER TYPE. This is clearly going to be necessary > if we want extension types to be able to use this facility. The > only thing that I think might be controversial here is that I did > not add the ability to set pg_type.typelem. While that'd be easy > enough so far as ALTER TYPE is concerned, I'm not sure that we want > to encourage people to change it. The dependency rules mean that > the semantics of typelem aren't something you really want to change > after-the-fact on an existing type. Also, if we did allow it, any > existing SubscriptingRef.refelemtype values in stored views would > fail to be updated.
I'm curious what could be the use case for setting pg_type.typelem for subscripting? I don't see this that much controversial, but maybe I'm missing something. > On Thu, Dec 10, 2020 at 05:37:20AM +0100, Pavel Stehule wrote: > st 9. 12. 2020 v 22:59 odesÃlatel Tom Lane <t...@sss.pgh.pa.us> napsal: > > > 0002 makes use of that to support subscripting of hstore. I'm not > > sure how much we care about that from a functionality standpoint, > > but it seems like it might be good to have a contrib module testing > > that extensions can use this. Also, I thought possibly an example > > showing what's basically the minimum possible amount of complexity > > would be good to have. If people like this, I'll finish it up (it > > lacks docs) and add it. > > > > +1 using subscripts for hstore is nice idea Yeah, I also find it's a good suggestion, the implementation seems fine as well. As a side note, I'm surprised hstore doesn't have any functionality to update values, except hstore_concat.
