RE: test_decoding assertion failure for the loss of top-sub transaction relationship

Dear Sawada-san,

Thank you for reviewing HEAD patch! PSA v3 patch.

> +# Test that we can force the top transaction to do timetravel when one of sub
> +# transactions needs that. This is necessary when we restart decoding
> from RUNNING_XACT
> +# without the wal to associate subtransaction to its top transaction.
> 
> I don't think the second sentence is necessary.
> 
> ---
> The last decoding
> +# starts from the first checkpoint and NEW_CID of "s0_truncate"
> doesn't mark the top
> +# transaction as catalog modifying transaction. In this scenario, the
> enforcement sets
> +# needs_timetravel to true even if the top transaction is regarded as
> that it does not
> +# have catalog changes and thus the decoding works without a
> contradition that one
> +# subtransaction needed timetravel while its top transaction didn't.
> 
> I don't understand the last sentence, probably it's a long sentence.
> 
> How about the following description?
> 
> # Test that we can handle the case where only subtransaction is marked
> as containing
> # catalog changes. The last decoding starts from NEW_CID generated by
> "s0_truncate" and
> # marks only the subtransaction as containing catalog changes but we
> don't create the
> # association between top-level transaction and subtransaction yet.
> When decoding the
> # commit record of the top-level transaction, we must force the
> top-level transaction
> # to do timetravel since one of its subtransactions is marked as
> containing catalog changes.

Seems good, I replaced all of comments to yours.

> + elog(DEBUG2, "forced transaction %u to do timetravel due to one of
> its subtransaction",
> + xid);
> + needs_timetravel = true;
> 
> I think "one of its subtransaction" should be "one of its subtransactions".

Fixed. 

Best Regards,
Hayato Kuroda
FUJITSU LIMITED