Re: [bugfix] commit timestamps ERROR on lookup of FrozenTransactionId

Hi,

On 2016-11-23 20:58:22 +0800, Craig Ringer wrote:
> Today I ran into an issue where commit timestamp lookups were failing with
>
>         ERROR: cannot retrieve commit timestamp for transaction 2
>
> which is of course FrozenTransactionId.
>
> TransactionIdGetCommitTsData(...) ERRORs on !TransactionIdIsNormal(),
> which I think is wrong. Attached is a patch to make it return 0 for
> FrozenTransactionId and BootstrapTransactionId, like it does for xids
> that are too old.

Why? It seems quite correct to not allow lookups for special case
values, as it seems sensible to give them special treatmeant at the call
site?


> IMO this should be back-patched to 9.6 and, without the TAP test part,
> to 9.5.

Why would we want to backpatch a behaviour change, where arguments for
the current and proposed behaviour exists?

Andres