I have started to learn postgresql. While going through the WAL dump saw
the below records,
rmgr: Heap2 len (rec/tot): 60/ 60, tx: 0, lsn:
4F/CFF1F0F8, prev 4F/CFF1EB70, desc: CLEAN remxid 0, blkref #0: rel
1663/16385/1259 blk 1301
rmgr: Heap2 len (rec/tot): 60/ 60, tx: 0, lsn:
4F/CF26F808, prev 4F/CF26F7C0, desc: CLEAN remxid 0, blkref #0: rel
1663/16385/3312732 blk 2634
rmgr: Heap2 len (rec/tot): 56/ 56, tx: 79718109, lsn:
4F/CF96D970, prev 4F/CF96D930, desc: CLEAN remxid 0, blkref #0: rel
1663/16385/209012 blk 6621
Wanted to know more about these,
1. Are "CLEAN" vacuum records ? If not, what are those ?
2. Why is the transaction id "0" ?
3. What does these records do ?
Postgresql version : 10.6
