On Thu, 7 Oct 2021 at 6:41 PM, Alvaro Herrera <alvhe...@alvh.no-ip.org> wrote:
> On 2021-Oct-07, Amul Sul wrote: > > > While reading this commit (ff9f111bce24), wondered can't we skip > > missingContrecPtr global variable declaration and calculate that from > > abortedRecPtr value whenever it needed. IIUC, missingContrecPtr is the > > next page to the page that abortedRecPtr contain and that can be > > calculated as "abortedRecPtr + (XLOG_BLCKSZ - (abortedRecPtr % > > XLOG_BLCKSZ))", thoughts? Please correct me if I'm missing something, > > thanks. > > I don't think that works -- what if the missing record is not on the > next page but on some future one? Imagine an enormously large record > that starts on segment 1, covers all of segment 2 and ends in segment 3. > We could have flushed segment 2 already, so with your idea we would skip > ahead only to that position, but really we need to skip all the way to > the first page of segment 3. > > This is easier to imagine if you set wal segment size to 1 MB, but it is > possible with the default segment size too, since commit records can be > arbitrarily large, and "logical message" records as well. Make sense, thanks for the explanation. Regards, Amul -- Regards, Amul Sul EDB: http://www.enterprisedb.com
