Hello, Horiguchi-san At Monday, July 6, 2020 05:13:40 +0000, "Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>" wrote in > > > after WAL buffer is filled up to the requested position. So when it > > > crosses segment boundary we know the all past corss segment-boundary > > > records are stable. That means all we need to remember is only the > > > position of the latest corss-boundary record. > > > > I could not agree. In the following case, it may not work well. > > - record-A and record-B (record-B is a newer one) is copied, and > > - lastSegContRecStart/End points to record-B's, and > > - FlushPtr is proceeded to in the middle of record-A. > > IIUC, that means record-B is a cross segment-border record and we hav e > flushed beyond the recrod-B. In that case crash recovery afterwards > can read the complete record-B and will finish recovery *after* the > record-B. That's what we need here.
I'm sorry I didn't explain enough. Record-A and Record-B are cross segment-border records. Record-A spans segment X and X+1 Record-B spans segment X+2 and X+3. If both records have been inserted to WAL buffer, lastSegContRecStart/End points to Record-B. If a writer flushes upto the middle of segment-X+1, NotifyStableSegments() allows the writer to notify segment-X. Is my understanding correct? Regards Ryo Matsumrua
