On 8 March 2018 at 12:34, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Thu, Mar 8, 2018 at 11:57 AM, Amit Khandekar <amitdkhan...@gmail.com> > wrote: >> On 8 March 2018 at 09:15, Pavan Deolasee <pavan.deola...@gmail.com> wrote: >>> For example, with your patches applied: >>> >>> CREATE TABLE pa_target (key integer, val text) >>> PARTITION BY LIST (key); >>> CREATE TABLE part1 PARTITION OF pa_target FOR VALUES IN (1); >>> CREATE TABLE part2 PARTITION OF pa_target FOR VALUES IN (2); >>> INSERT INTO pa_target VALUES (1, 'initial1'); >>> >>> session1: >>> BEGIN; >>> UPDATE pa_target SET val = val || ' updated by update1' WHERE key = 1; >>> UPDATE 1 >>> postgres=# SELECT * FROM pa_target ; >>> key | val >>> -----+----------------------------- >>> 1 | initial1 updated by update1 >>> (1 row) >>> >>> session2: >>> UPDATE pa_target SET val = val || ' updated by update2', key = key + 1 WHERE >>> key = 1 >>> <blocks> >>> >>> session1: >>> postgres=# COMMIT; >>> COMMIT >>> >>> <session1 unblocks and completes its UPDATE> >>> >>> postgres=# SELECT * FROM pa_target ; >>> key | val >>> -----+----------------------------- >>> 2 | initial1 updated by update2 >>> (1 row) >>> >>> Ouch. The committed updates by session1 are overwritten by session2. This >>> clearly violates the rules that rest of the system obeys and is not >>> acceptable IMHO. >>> >>> Clearly, ExecUpdate() while moving rows between partitions is missing out on >>> re-constructing the to-be-updated tuple, based on the latest tuple in the >>> update chain. Instead, it's simply deleting the latest tuple and inserting a >>> new tuple in the new partition based on the old tuple. That's simply wrong. >> >> You are right. This need to be fixed. This is a different issue than >> the particular one that is being worked upon in this thread, and both >> these issues have different fixes. >> > > I also think that this is a bug in the original patch and won't be > directly related to the patch being discussed.
Yes. Will submit a patch for this in a separate thread. -- Thanks, -Amit Khandekar EnterpriseDB Corporation The Postgres Database Company
