Re: BUG #15159: Duplicate records for same primary key

On Tue, Apr 17, 2018 at 04:37:51AM +0000, PG Bug reporting form wrote:
> 1. Primary key is created to have unique records, then how two records are
> being created/inserted?
> 2. After delete of malicious record, how other record is showing up to be
> having duplicate records? Am I missing anything to be checked ?

The bug nick-named around as freeze-the-dead. 9.3.21 has fixed an issue
where tuples not normally visible, or marked as dead could come back to
life and become visible. That's this entry in the release notes:
"Fix vacuuming of tuples that were updated while key-share locked (Andres
Freund, Álvaro Herrera)
In some cases VACUUM would fail to remove such tuples even though they
are now dead, leading to assorted data corruption scenarios."

And here are the corresponding release notes:
https://www.postgresql.org/docs/devel/static/release-9-3-21.html

So you first need to update this version of PostgreSQL, and then some
manual cleanup of those duplicated tuples is needed with for example a
tid mathing.
--
Michael