Michael Paquier <michael@paquier.xyz> writes:
> I can see that this has already been committed as 9f71e10d65, but are
> you sure that this is correct? I didn't take the time to reply back,
> because I got the feeling that even what I proposed is not correct.
> The previous code was careful enough to look at the information from
> info2 only *through* the attribute map, which is not what this new
> code is doing. Rather than looking directly at the elements in info2
> at each iteration, shouldn't this stuff loop over the elements in
> attmap->attnums for each info1->ii_IndexAttrNumbers[i]?
I think it's OK as is. What we are comparing in the modified logic
is whether index columns at the same column positions are expressions or
not, and that's not a matter for mapping. Once we've verified that
the current column is a non-expression in both indexes, then it's
appropriate to use the attmap to see whether the columns correspond.
(Or to put it another way: running "column zero" through the
attmap is always the wrong thing.)
regards, tom lane
