Re: clean up docs for v12

Hi,

On 2019-04-22 14:17:48 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On 2019-04-22 13:27:17 -0400, Tom Lane wrote:
> >> I wonder
> >> also if it wouldn't be smart to explicitly check that the "guaranteeing"
> >> column is not attisdropped.
> 
> > Yea, that probably would be smart.  I don't think there's an active
> > problem, because we remove NOT NULL when deleting an attribute, but it
> > seems good to be doubly sure / explain why that's safe:
> > 		/* Remove any NOT NULL constraint the column may have */
> > 		attStruct->attnotnull = false;
> > I'm a bit unsure whether to make it an assert, elog(ERROR) or just not
> > assume column presence?
> 
> I'd just make the code look like
> 
>         /*
>          * If it's NOT NULL then it must be present in every tuple,
>          * unless there's a "missing" entry that could provide a non-null
>          * value for it.  Out of paranoia, also check !attisdropped.
>          */
>         if (att->attnotnull &&
>             !att->atthasmissing &&
>             !att->attisdropped)
>             guaranteed_column_number = attnum;
> 
> I don't think the extra check is so expensive as to be worth obsessing
> over.

Pushed. Did so separately from Justin's changes, since this is a small
functional change.

Greetings,

Andres Freund