On Fri, Nov 16, 2018 at 4:07 AM Kevin Grittner <kgri...@gmail.com> wrote: > > On Thu, Nov 15, 2018 at 3:03 AM Kuntal Ghosh <kuntalghosh.2...@gmail.com> > wrote: > > > The test multiple-row-versions is failing because of the > > above-discussed scenario. I've attached the regression diff file and > > the result output file for the same. Here is a brief summary of the > > test w.r.t. heap: > > > > Step 1: T1-> BEGIN; Read FROM t where id=1000000; > > Step 2: T2-> BEGIN; UPDATE t where id=1000000; COMMIT; (creates T1->T2) > > Step 3: T3-> BEGIN; UPDATE t where id=1000000; Read FROM t where id=500000; > > Step 4: T4-> BEGIN; UPDATE t where id= 500000; Read FROM t where id=1; > > COMMIT; (creates T3->T4) > > Step 5: T3-> COMMIT; > > Step 6: T1-> UPDATE t where id=1; COMMIT; (creates T4->T1,) > > > > At step 6, when the update statement is executed, T1 is rolled back > > because of T3->T4->T1. > > > > But for zheap, step 3 also creates a dependency T1->T3 because of > > in-place update. When T4 commits in step 4, it marks T3 as doomed > > because of T1 --> T3 --> T4. Hence, in step 5, T3 is rolled back. > > If I understand this, no permutation (order of execution of the > statements in a set of concurrent transactions vulnerable to > serialization anomalies) which have succeeded with the old storage > engine now fail with zheap; what we have with zheap is an earlier > failure in one case. More importantly, zheap doesn't create any false > negatives (cases where a serialization anomaly is missed). >
Your understanding is correct. Thanks for sharing your feedback. > I would say this should be considered a resounding success. We should > probably add an alternative result file to cover this case, but > otherwise I don't see anything which requires action. > > Congratulations on making this work so well! > Thanks. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
