On Sat, Sep 30, 2023 at 08:39:37PM -0400, Tom Lane wrote:
> 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.
FWIW, I was thinking about a case like that with 2 index attributes:
info1->attr[0] = 0, info1->attr[1] = 1
info2->attr[0] = 1, info2->attr[1] = 0
With a mapping from info2 to info1 like that:
attmap[0] = 1, attmap[1] = 0.
The code before 9f71e10d6 would have accessed an incorrect pointer.
The new code would return false, which would not be correct if the
expressions stored in ii_Expressions for info1/attr0 and info2/attr1
match?
--
Michael
