On Mon, Jul 8, 2019 at 9:00 AM Thomas Munro <thomas.mu...@gmail.com> wrote: > > On Wed, Jun 26, 2019 at 2:46 AM Ildar Musin <il...@adjust.com> wrote: > > Attached is a simple patch that uses subxid instead of top-level xid > > in ReorderBufferAddNewTupleCids() call. It seems to fix the bug, but > > i'm not sure that this is a valid change. Can someone please verify it > > or maybe suggest a better solution for the issue? >
I've reproduced this issue with script Ildar provided. I don't find out the root cause yet and I'm not sure the patch takes a correct way to fix this. In my environment, I got the following pg_waldump output and the logical decoding failed at 0/019FA058 when processing NEW_CID. 90489 rmgr: Transaction len (rec/tot): 38/ 38, tx: 1999, lsn: 0/019F9E80, prev 0/019F9E38, desc: ASSIGNMENT xtop 1998: subxacts: 1999 90490 rmgr: Standby len (rec/tot): 405/ 405, tx: 0, lsn: 0/019F9EA8, prev 0/019F9E80, desc: RUNNING_XACTS nextXid 2000 latestCompletedXid 1949 oldestRunningXid 1836; 48 xacts: 1990 1954 1978 1850 1944 1972 1940 1924 1906 1970 1985 1998 1966 1987 1975 1858 1914 1982 1958 1840 1920 1926 1992 1962 1 90490 910 1950 1874 1928 1974 1968 1946 1912 1918 1996 1922 1930 1964 1952 1994 1934 1980 1836 1984 1960 1956 1916 1908 1938 90491 rmgr: Heap2 len (rec/tot): 60/ 60, tx: 1999, lsn: 0/019FA058, prev 0/019F9EA8, desc: NEW_CID rel 1663/12678/2615; tid 11/59; cmin: 0, cmax: 4294967295, combo: 4294967295 90492 rmgr: Heap len (rec/tot): 127/ 127, tx: 1999, lsn: 0/019FA098, prev 0/019FA058, desc: INSERT off 59 flags 0x00, blkref #0: rel 1663/12678/2615 blk 11 I thought that the logical decoding doesn't create ReorderBufferTXN of xid=1999 when processing NEW_CID since it decodes ASSIGNMENT of xid=1999 beforehand. But what actually happen is that it skips NEW_CID since the state of snapshot builder is SNAPBUILD_BUILDING_SNAPSHOT yet and then the state becomes SNAPBUILD_FULL_SNAPSHOT when processing RUNNING_XACTS , and therefore it creates two ReorderBufferTXN entries for xid = 1999 and xid = 1998 as top-level transactions when processing NEW_CID (ReorderBufferXidSetCatalogChanges creates xid=1999 and ReorderBufferAddNewTupleCids creates xid = 1998). And therefore it got the assertion failure when adding ReorderBufferTXN of xid = 1998. I'll look into this more deeply tomorrow. Regards, -- Masahiko Sawada NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
