Hi All, Attaching POC patch that throws an error in the case of a concurrent update to an already deleted tuple due to UPDATE of partition key[1].
In a normal update new tuple is linked to the old one via ctid forming a chain of tuple versions but UPDATE of partition key[1] move tuple from one partition to an another partition table which breaks that chain. Consider a following[2] concurrent update case where one session trying to update a row that's locked for a concurrent update by the another session cause tuple movement to the another partition. create table foo (a int2, b text) partition by list (a); create table foo1 partition of foo for values IN (1); create table foo2 partition of foo for values IN (2); insert into foo values(1, 'ABC'); ----------- session 1 ----------- postgres=# begin; BEGIN postgres=# update foo set a=2 where a=1; UPDATE 1 ----------- session 2 ----------- postgres=# update foo set b='EFG' where a=1; ….. wait state …… ----------- session 1 ----------- postgres=# commit; COMMIT ----------- session 2 ----------- UPDATE 0 This UPDATE 0 is the problematic, see Greg Stark's update[3] explains why we need an error. To throw an error we need an indicator that the targeted row has been already moved to the another partition, and for that setting a ctid.ip_blkid to InvalidBlockId looks viable option for now. The attached patch incorporates the following logic suggested by Amit Kapila[4]: "We can pass a flag say row_moved (or require_row_movement) to heap_delete which will in turn set InvalidBlockId in ctid instead of setting it to self. Then the ExecUpdate needs to check for the same and return an error when heap_update is not successful (result != HeapTupleMayBeUpdated)." 1] https://postgr.es/m/CAJ3gD9do9o2ccQ7j7%2BtSgiE1REY65XRiMb%3DyJO3u3QhyP8EEPQ%40mail.gmail.com 2] With https://postgr.es/m/CAJ3gD9fzD4jBpv+zXqZYnW=h9JXUFG9E7NGdA9gR_JJbOj=q...@mail.gmail.com patch applied. 3] https://postgr.es/m/CAM-w4HPis7rbnwi%2BoXjnouqMSRAC5DeVcMdxEXTMfDos1kaYPQ%40mail.gmail.com 4] https://postgr.es/m/CAA4eK1KEZQ%2BCyXbBzfn1jFHoEfa_OemDLhLyy7xfD1QUZLo1DQ%40mail.gmail.com Regards, Amul
0001-POC-Invalidate-ip_blkid-v1.patch
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