On Thu, 14 Jan 2021 at 15:32, Kyotaro Horiguchi wrote: > At Thu, 14 Jan 2021 06:46:35 +0000, Li Japin <japi...@hotmail.com> wrote in >> >> On Jan 14, 2021, at 12:56 PM, Ashutosh Bapat >> <ashutosh.bapat....@gmail.com<mailto:ashutosh.bapat....@gmail.com>> wrote: >> >> Hi Japin, >> Thanks for the report. >> >> I think that comment is correct. It refers to the following code >> blocks of XLogSendPhysical() >> >> 2744 /* >> 2745 * OK to read and send the slice. >> 2746 */ >> 2747 resetStringInfo(&output_message); >> 2748 pq_sendbyte(&output_message, 'w'); >> 2749 >> 2750 pq_sendint64(&output_message, startptr); /* dataStart */ >> 2751 pq_sendint64(&output_message, SendRqstPtr); /* walEnd */ >> 2752 pq_sendint64(&output_message, 0); /* sendtime, filled in last */ >> >> 2803 * Fill the send timestamp last, so that it is taken as late >> as possible. >> 2804 */ >> 2805 resetStringInfo(&tmpbuf); >> 2806 pq_sendint64(&tmpbuf, GetCurrentTimestamp()); >> 2807 memcpy(&output_message.data[1 + sizeof(int64) + sizeof(int64)], >> 2808 tmpbuf.data, sizeof(int64)); >> 2809 >> 2810 pq_putmessage_noblock('d', output_message.data, output_message.len); >> >> >> After a quick search, I found that WalSndPrepareWrite and WalSndWriteData >> are always pairs [1]. >> IIUC the space of sendtime leave by WalSndPrepareWrite, it always fill out >> by WalSndWriteData. >> >> >> WalSndWriteData() also fills the timestamp there but it may not always >> be used with WalSndPrepareWrite, at least theoretically. So it's the >> XLogSendPhysical() that it's referring to. > > The two functions are the body of two logical-decoding API > functions. They are assumed to be called in that order. See > OutputPluginWrite() for the restriction. The sequence of the two > logica-decoding funcitons and the code block in XLogSendPhysical are > parallels in (theoretically) different protocols. >
Is that mean the sendtime of WalSndPrepareWrite always fill out by WalSndWriteData? If it is, I think we should modify the comment in WalSndPrepareWrite. -- Regrads, Japin Li. ChengDu WenWu Information Technology Co.,Ltd.
