Re: amcheck: fix bug of missing corruption in allequalimage validation - Mailing list pgsql-hackers

> On Feb 25, 2026, at 14:43, Kirill Reshke <reshkekirill@gmail.com> wrote:
>
> On Wed, 25 Feb 2026 at 08:12, Chao Li <li.evan.chao@gmail.com> wrote:
>>
>> Hi,
>>
>> While poking around the code in contrib/amcheck/verify_nbtree.c, I noticed the following block:
>> ```
>>        if (allequalimage && !_bt_allequalimage(indrel, false))
>>        {
>>                bool            has_interval_ops = false;
>>
>>                for (int i = 0; i < IndexRelationGetNumberOfKeyAttributes(indrel); i++)
>>                        if (indrel->rd_opfamily[i] == INTERVAL_BTREE_FAM_OID)
>>                        {
>>                                has_interval_ops = true;
>>                                ereport(ERROR,
>>                                                (errcode(ERRCODE_INDEX_CORRUPTED),
>>                                                 errmsg("index \"%s\" metapage incorrectly indicates that
deduplicationis safe", 
>>                                                                RelationGetRelationName(indrel)),
>>                                                 has_interval_ops
>>                                                 ? errhint("This is known of \"interval\" indexes last built on a
versionpredating 2023-11.") 
>>                                                 : 0));
>>                        }
>>        }
>> ```
>>
>> My initial impression was that has_interval_ops was unneeded and could be removed, as it is always true at the point
ofuse. I originally thought this would just be a tiny refactoring. 
>>
>> However, on second thought, I realized that having the ereport inside the for loop is actually a bug. If
allequalimageis set in the metapage but _bt_allequalimage says it’s unsafe, we should report corruption regardless of
thecolumn types. In the current code, if the index does not contain an interval opfamily, the loop finishes without
reachingthe ereport, thus silencing the corruption. 
>>
>> This patch moves the ereport out of the for loop. This ensures that corruption is reported unconditionally, while
keepingthe interval-specific hint optional. 
>>
>> Best regards,
>> --
>> Chao Li (Evan)
>> HighGo Software Co., Ltd.
>> https://www.highgo.com/
>>
>
>
> uff, this looks like a clear oversight of d70b176.
>
> Before d70b176 it was like this:
>
>
https://github.com/postgres/postgres/blame/fb9dff76635d4c32198f30a3cb503588d557d156/contrib/amcheck/verify_nbtree.c#L386-L399
>
>

Thanks for pointing out the origin code that seems to prove my fix is correct. But my patch adds “break” in the “for”
loop,which makes it slightly better than the original version. 

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/