Thread: Possible mistake in Section 63.6 - 9.6devel Documentation
Hello,
It has been mentioned in Section 63.6 that the first two fields in PageHeaderData track the most recent WAL entry related to the page. However, I am not sure how pd_checksum is related to WAL. Could it be possible that the sentence has been carried over from previous versions of the documentations without considering the change to the second field in PageHeaderData?
Thanks,
Vignesh.
On Tue, Jul 21, 2015 at 6:54 AM, Vignesh Raghunathan <vignesh.pgsql@gmail.com> wrote: > Hello, > > It has been mentioned in Section 63.6 that the first two fields in > PageHeaderData track the most recent WAL entry related to the page. However, > I am not sure how pd_checksum is related to WAL. Could it be possible that > the sentence has been carried over from previous versions of the > documentations without considering the change to the second field in > PageHeaderData? Yes, the documentation is mistaken. The two bytes of pd_tli have been switched to pd_checksum in 9.3, hence only the first field is relevant for WAL, aka pd_lsn. Looking at this portion of the docs I think that it should be updated as attached, mentioning pd_checksum as well. -- Michael
Attachment
On Tue, Jul 21, 2015 at 9:59 AM, Michael Paquier <michael.paquier@gmail.com> wrote: > On Tue, Jul 21, 2015 at 6:54 AM, Vignesh Raghunathan > <vignesh.pgsql@gmail.com> wrote: >> Hello, >> >> It has been mentioned in Section 63.6 that the first two fields in >> PageHeaderData track the most recent WAL entry related to the page. However, >> I am not sure how pd_checksum is related to WAL. Could it be possible that >> the sentence has been carried over from previous versions of the >> documentations without considering the change to the second field in >> PageHeaderData? > > Yes, the documentation is mistaken. The two bytes of pd_tli have been > switched to pd_checksum in 9.3, hence only the first field is relevant > for WAL, aka pd_lsn. Looking at this portion of the docs I think that > it should be updated as attached, mentioning pd_checksum as well. Also the type of pd_lsn in the Table 63-3 should be PageXLogRecPtr. Regards, -- Fujii Masao
On Thu, Sep 10, 2015 at 12:42 AM, Fujii Masao <masao.fujii@gmail.com> wrote: > On Tue, Jul 21, 2015 at 9:59 AM, Michael Paquier > <michael.paquier@gmail.com> wrote: >> On Tue, Jul 21, 2015 at 6:54 AM, Vignesh Raghunathan >> <vignesh.pgsql@gmail.com> wrote: >>> Hello, >>> >>> It has been mentioned in Section 63.6 that the first two fields in >>> PageHeaderData track the most recent WAL entry related to the page. However, >>> I am not sure how pd_checksum is related to WAL. Could it be possible that >>> the sentence has been carried over from previous versions of the >>> documentations without considering the change to the second field in >>> PageHeaderData? >> >> Yes, the documentation is mistaken. The two bytes of pd_tli have been >> switched to pd_checksum in 9.3, hence only the first field is relevant >> for WAL, aka pd_lsn. Looking at this portion of the docs I think that >> it should be updated as attached, mentioning pd_checksum as well. > > Also the type of pd_lsn in the Table 63-3 should be PageXLogRecPtr. Yep. See attached FWIW. -- Michael
Attachment
On Thu, Sep 10, 2015 at 3:05 PM, Michael Paquier <michael.paquier@gmail.com> wrote: > On Thu, Sep 10, 2015 at 12:42 AM, Fujii Masao <masao.fujii@gmail.com> wrote: >> On Tue, Jul 21, 2015 at 9:59 AM, Michael Paquier >> <michael.paquier@gmail.com> wrote: >>> On Tue, Jul 21, 2015 at 6:54 AM, Vignesh Raghunathan >>> <vignesh.pgsql@gmail.com> wrote: >>>> Hello, >>>> >>>> It has been mentioned in Section 63.6 that the first two fields in >>>> PageHeaderData track the most recent WAL entry related to the page. However, >>>> I am not sure how pd_checksum is related to WAL. Could it be possible that >>>> the sentence has been carried over from previous versions of the >>>> documentations without considering the change to the second field in >>>> PageHeaderData? >>> >>> Yes, the documentation is mistaken. The two bytes of pd_tli have been >>> switched to pd_checksum in 9.3, hence only the first field is relevant >>> for WAL, aka pd_lsn. Looking at this portion of the docs I think that >>> it should be updated as attached, mentioning pd_checksum as well. >> >> Also the type of pd_lsn in the Table 63-3 should be PageXLogRecPtr. > > Yep. See attached FWIW. Thanks! Applied. Regards, -- Fujii Masao