On Tue, Sep 19, 2017 at 11:42 AM, Thomas Munro < thomas.mu...@enterprisedb.com> wrote:
> On Fri, Sep 1, 2017 at 5:11 PM, Thomas Munro > <thomas.mu...@enterprisedb.com> wrote: > > On Wed, Jun 28, 2017 at 11:21 AM, Thomas Munro > > <thomas.mu...@enterprisedb.com> wrote: > >> [ssi-parallel-v5.patch] > > > > Rebased. > > Rebased again. > During testing of this patch, I found some behavior difference with the support of parallel query, while experimenting with the provided test case in the patch. But I tested the V6 patch, and I don't think that this version contains any fixes other than rebase. Test steps: CREATE TABLE bank_account (id TEXT PRIMARY KEY, balance DECIMAL NOT NULL); INSERT INTO bank_account (id, balance) VALUES ('X', 0), ('Y', 0); Session -1: BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; SELECT balance FROM bank_account WHERE id = 'Y'; Session -2: BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; SET max_parallel_workers_per_gather = 2; SET force_parallel_mode = on; set parallel_setup_cost = 0; set parallel_tuple_cost = 0; set min_parallel_table_scan_size = 0; set enable_indexscan = off; set enable_bitmapscan = off; SELECT balance FROM bank_account WHERE id = 'X'; Session -1: update bank_account set balance = 10 where id = 'X'; Session -2: update bank_account set balance = 10 where id = 'Y'; ERROR: could not serialize access due to read/write dependencies among transactions DETAIL: Reason code: Canceled on identification as a pivot, during write. HINT: The transaction might succeed if retried. Without the parallel query of select statement in session-2, the update statement in session-2 is passed. Regards, Hari Babu Fujitsu Australia