> 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.