Has this been fixed? I think we did.
--------------------------------------------------------------------------- Tom Lane wrote: > I have been looking at an example of the "no one parent tuple found" > VACUUM error provided by Mario Weilguni. It appears to me that VACUUM > is getting confused by a tuple that looks like so in pg_filedump: > > Item 4 -- Length: 249 Offset: 31616 (0x7b80) Flags: USED > OID: 0 CID: min(240) max(18) XID: min(5691267) max(6484551) > Block Id: 1 linp Index: 1 Attributes: 38 Size: 40 > infomask: 0x3503 >(HASNULL|HASVARLENA|XMIN_COMMITTED|XMAX_COMMITTED|MARKED_FOR_UPDATE|UPDATED) > > Notice that the t_ctid field is not pointing to this tuple, but to a > different item on the same page (which in fact is an unused item). > This causes VACUUM to believe that the tuple is part of an update chain. > But in point of fact it is not part of a chain (indeed there are *no* > chains in the test relation, thus leading to the observed failure). > > As near as I can tell, the sequence of events was: > > 1. this row was updated by a transaction that stored the updated version > in lineindex 1, but later aborted. t_ctid is left pointing to linp 1. > > 2. Some other transaction came along, marked the row FOR UPDATE, and > committed (with no actual update). > > So we now have XMAX_COMMITTED and t_ctid != t_self, which looks way too > much like a tuple that's been updated, when in fact it is the latest > good version of its row. > > I think an appropriate fix would be to reset t_ctid to equal t_self > whenever we clear XMAX_INVALID, which in practice means heap_delete and > heap_mark4update need to do this. (heap_update also clears > XMAX_INVALID, but of course it's setting t_ctid to point to the updated > tuple.) > > Comments? > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 6: Have you searched our list archives? > > http://archives.postgresql.org > -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
