Re: clean up docs for v12

Andres Freund <andres(at)anarazel(dot)de> writes:
> The computation of that variable above has:

> * If the column is possibly missing, we can't rely on its (or
> * subsequent) NOT NULL constraints to indicate minimum attributes in
> * the tuple, so stop here.
> */
> if (att->atthasmissing)
> break;

BTW, why do we have to stop? ISTM that a not-null column without
atthasmissing is enough to prove this, regardless of the state of prior
columns. (This is assuming that you trust attnotnull for this, which
as I said I don't, but that's not relevant to this question.) I wonder
also if it wouldn't be smart to explicitly check that the "guaranteeing"
column is not attisdropped.

> I think just reformulating that to something like

> /*
> * Check if it's guaranteed that all the desired attributes are available
> * in the tuple (but still possibly NULL), by dint of either the last
> * to-be-deformed column being NOT NULL, or subsequent ones not accessed
> * here being NOT NULL. If that's not guaranteed the tuple headers natt's
> * has to be checked, and missing attributes potentially have to be
> * fetched (using slot_getmissingattrs().
> */

> should make that clearer?

OK by me.

regards, tom lane