On Fri, Apr 3, 2020 at 9:17 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > > On Fri, Apr 3, 2020 at 9:02 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > On Fri, Apr 3, 2020 at 8:55 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > > > I think now I got the reason. Basically, both of these records are > > > storing the FPW, and FPW size can vary based on the hole size on the > > > page. If hold size is smaller the image length will be more, the > > > image_len= BLCKSZ-hole_size. So in subsequent records, the image size > > > is bigger. > > > > > > > This means if we always re-create the database or may be keep > > full_page_writes to off, then we should get consistent WAL usage data > > for all tests. > > With new database, it is always the same. But, with full-page write, > I could see one of the create index is writing extra wal and if we > change the older then the new create index at that place will write > extra wal. I guess that could be due to a non-in place update in some > of the system tables.
I have analyzed the WAL and there could be multiple reasons for the same. With small data, I have noticed that while inserting in the system index there was a Page Split and that created extra WAL. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com