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). 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! -- Kevin Grittner VMware vCenter Server https://www.vmware.com/
