| From: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> |
|---|---|
| To: | Xiaoyulei <xiaoyulei(at)huawei(dot)com> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: does tuple store subtransaction id in it? |
| Date: | 2015-06-17 02:35:14 |
| Message-ID: | CAJrrPGc8BVYaDu+PBMaP4KuN13hJ6GncRc0s2jh0z55yGaM4DA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jun 16, 2015 at 1:08 PM, Xiaoyulei <xiaoyulei(at)huawei(dot)com> wrote:
> In XidInMVCCSnapshot, it will check xid from tuple if is in snapshot->subxip. It means tuple store subtransaction?
Tuple stores only the transaction id related to the operation. This
can be either main transaction id or sub transaction id.
> But in PushTransaction, I see TransactionState.subTransaction will assign currentSubTransactionId, currentSubTransactionId will reinitialize in StartTransaction. So I think tuple should not store subtransaction id.
>
> I am confuse about this. If subtransaction id will reinitialize every start time. How to judge it is a subtransaction from xid in tuple?
StartTransaction is called only once per transaction.Further on for
sub transactions it calls only startSubTransaction.
Hope this answers your question.
Regards,
Hari Babu
Fujitsu Australia
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