From: | Michael Paquier <michael(at)paquier(dot)xyz> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | exclusion(at)gmail(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org |
Subject: | Re: BUG #18135: Incorrect memory access occurs when attaching a partition with an index |
Date: | 2023-10-02 02:56:35 |
Message-ID: | ZRoxY3X1tGZRZQ2A@paquier.xyz |
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Lists: | pgsql-bugs |
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
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