Re: pg_authid has duplicated rows

On July 23, 2018 1:33:11 PM PDT, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
>On 2018-Jul-23, Andres Freund wrote:
>
>> Hi,
>>
>> On 2018-07-23 21:03:32 +0300, Mariel Cherkassky wrote:
>> > Today I faced a situation where I saw a postgresql 9.2 database
>that had
>> > duplicated rows in pg_autid. I saw 6 roles while 3 of them were
>duplicated
>> > (3 uniques rolenames in total). I checked and the oid of the
>duplicates
>> > were the same oid as the originals. The solution was running vacuum
>on the
>> > table but I wanted to understand how this situation was created ?
>Why even
>> > with unique index on the rolname I saw duplicated values for
>rolname ?
>>
>> That suggests some form of corruption. Which version of 9.2 did this
>> occur on? Did you have any OS level crashes? Ran with fsync=off?
>
>I have vague memories of seeing this recently.  Can you please show

It's at least one of the potential effects of the out-of-date shared relcache bug I recently fixed (but wasn't
backpatchedto 9.2, as it's unsupported). 

Andres

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