Re: Don't deform column-by-column in composite_to_json

> On 2 Feb 2019, at 00:21, Andres Freund <andres@anarazel.de> wrote:

> In https://postgr.es/m/20190201162404.onngi77f26baem4g%40alap3.anarazel.de
> I noticed that composite_to_json() deforms column-by-column. Given that
> it always processes all columns, that seems quite the waste of resources.
> 
> In some quick'n dirty dirty testing this gives a ~4% benefit in a table
> without nulls and varlenas, and ~7% in one with both. I assume that if
> one were to test with a bit wider table the win would be bigger.
> 
> A short test shows that it'd be slower to allocate nulls/values with
> palloc rather than using MaxHeapAttributeNumber. Given that only output
> functions are called from within composite_to_json(), I think that's ok.

Nice catch, patch looks good to me.  composite_to_jsonb() has the same
construction, processing every attribute.  Should it get a similar patch as
this?

cheers ./daniel