Re: [HACKERS] SERIALIZABLE with parallel query
| От | Haribabu Kommi |
|---|---|
| Тема | Re: [HACKERS] SERIALIZABLE with parallel query |
| Дата | |
| Msg-id | CAJrrPGdMtQNd2yc4gD38byXQ+MdVEjHbonovQk1iD6+LvTLNBw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [HACKERS] SERIALIZABLE with parallel query (Thomas Munro <thomas.munro@enterprisedb.com>) |
| Ответы |
Re: [HACKERS] SERIALIZABLE with parallel query
|
| Список | pgsql-hackers |
On Tue, Sep 19, 2017 at 11:42 AM, Thomas Munro <thomas.munro@enterprisedb.com> wrote:
On Fri, Sep 1, 2017 at 5:11 PM, Thomas Munro
<thomas.munro@enterprisedb.com> wrote:
> On Wed, Jun 28, 2017 at 11:21 AM, Thomas Munro
> <thomas.munro@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
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