Re: Losing records in PostgreSQL 9.6

On 5/4/22 09:55, A G wrote:

Hi, 
thanks for your help.

My team is using Postgres 9.6.10 for an on-premise application (we are planing on upgrading to a newer Postgres version). Our application comes with Postgres running in a docker container with its data stored in a docker volume. Our software uses pg_dump / pg_restore to backup and restore the database.

Now we got a ticket from a customer where their database is missing rows from a table. There are 971 consecutive rows missing from the beginning of the table. The missing rows were inserted first. We find it also strange, that all the other tables don’t seem to be affected at all. It appears that there is only data loss in this single table.
Unfortunately, we don’t have access to the original database anymore and need to find out what happened through the backups the customer provides. We have one backup right after they installed and initially configured the application, which seems complete. Then there is another backup 10 months later where the first 971 rows are already missing in this one table.

If we exclude a manual deletion, which the customer denies,

There's more to PEBKAC than manual deletion.

we are wondering if it’s possible that Postgres 9.6 could lose some of its data through a storage or memory error and would create a “successful” pg_dump with only partial data? Is such a behaviour even thinkable with Postgres?

Do you have an idea what else could cause this issue?

Uncommitted transactions? 
* Purge job with a bug in it?
* Two different date columns (for example "transaction_date" and "posted_date") which are expected to be the same apparently not always.  Since the errors apparently happen at the beginning of the month, the purge job might have seen them as the previous month's records.

These are our dump and restore commands:
pg_dump -Fc --no-acl --no-owner -U acme -h 127.0.0.1 acme > acme.dump
pg_restore -d acme -n public -U acme -h 127.0.0.1 --jobs=4 acme.dump

We use just a single db user to access the database and we don’t use RLS.

Thank you.

Best regards,
Andreas

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