Re: pg_dumpall and restore

Rossi, Maria wrote:
> I upgraded our postgres database from V9.3 to V10.5. Used pg_dumpall then restore it to the new instance.
> After the restore, we notice that 1 table had duplicate rows, such that it was not able to create the primary key.
> I checked the old database, it does not have the dups.
> Has anyone encountered having dups rows loaded? Any idea what caused this and how to prevent?
>
> Your help would be much appreciated.

I don't believe that pg_dumpall miraculously duplicated the row.

You probably *do* have a duplicate row, and hence table corruption,
but I suspect that one of the rows is not in the index you used
to look for the row.

If you query:

SELECT * FROM tab WHERE id = 42;

the query will likely use the index on "id" and find only one of
the rows.

You should

SET enable_indexscan = off;
SET enable_indexonlyscan = off;

and then repeat the query, so that a sequential scan is used.

To fix, delete one of the rows and reindex.

You can identify a row by its tuple id:

SELECT ctid, * FROM tab WHERE id = 42;

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com