Re: Write Ahead Logging for Hash Indexes

On Wed, Aug 24, 2016 at 8:54 AM, Mark Kirkwood
<mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> wrote:
> On 24/08/16 12:09, Mark Kirkwood wrote:
>>
>> On 23/08/16 15:24, Amit Kapila wrote:
>>>
>>>
>>> Thoughts?
>>>
>>> Note - To use this patch, first apply latest version of concurrent
>>> hash index patch [2].
>>>
>>> [1] - https://commitfest.postgresql.org/10/647/
>>> [2] -
>>> https://www.postgresql.org/message-id/CAA4eK1LkQ_Udism-Z2Dq6cUvjH3dB5FNFNnEzZBPsRjw0haFqA@mail.gmail.com
>>>
>>>
>>
>> Firstly - really nice! Patches applied easily etc to latest version 10
>> checkout.
>>
>> I thought I'd test by initializing pgbench schema, adding a standby, then
>> adding some hash indexes and running pgbench:
>>
>> Looking on the standby:
>>
>> bench=# \d pgbench_accounts
>> Table "public.pgbench_accounts"
>> Column | Type | Modifiers
>> ----------+---------------+-----------
>> aid | integer | not null
>> bid | integer |
>> abalance | integer |
>> filler | character(84) |
>> Indexes:
>> "pgbench_accounts_pkey" PRIMARY KEY, btree (aid)
>> "pgbench_accounts_bid" hash (bid) <====
>>
>> bench=# \d pgbench_history
>> Table "public.pgbench_history"
>> Column | Type | Modifiers
>> --------+-----------------------------+-----------
>> tid | integer |
>> bid | integer |
>> aid | integer |
>> delta | integer |
>> mtime | timestamp without time zone |
>> filler | character(22) |
>> Indexes:
>> "pgbench_history_bid" hash (bid) <=====
>>
>>
>> they have been replicated there ok.
>>
>> However I'm seeing a hang on the master after a while:
>>
>> bench=# SELECT datname,application_name,state,now()-xact_start AS
>> wait,query FROM pg_stat_activity ORDER BY wait DESC;
>> datname | application_name | state | wait | query
>>
>> ---------+------------------+--------+-----------------+----------------------------------------------------------------------------------------------------------------
>> | walreceiver | idle | |
>> bench | pgbench | active | 00:31:38.367467 | INSERT INTO
>> pgbench_history (tid, bid, aid, delta, mtime) VALUES (921, 38, 251973,
>> -3868, CURRENT_TIMESTAMP);
>> bench | pgbench | active | 00:31:38.215378 | INSERT INTO
>> pgbench_history (tid, bid, aid, delta, mtime) VALUES (280, 95, 3954814,
>> 2091, CURRENT_TIMESTAMP);
>> bench | pgbench | active | 00:31:35.991056 | INSERT INTO
>> pgbench_history (tid, bid, aid, delta, mtime) VALUES (447, 33, 8355237,
>> 3438, CURRENT_TIMESTAMP);
>> bench | pgbench | active | 00:31:35.619798 | INSERT INTO
>> pgbench_history (tid, bid, aid, delta, mtime) VALUES (134, 16, 4839994,
>> -2443, CURRENT_TIMESTAMP);
>> bench | pgbench | active | 00:31:35.544196 | INSERT INTO
>> pgbench_history (tid, bid, aid, delta, mtime) VALUES (37, 73, 9620119, 4053,
>> CURRENT_TIMESTAMP);
>> bench | pgbench | active | 00:31:35.334504 | UPDATE
>> pgbench_branches SET bbalance = bbalance + -2954 WHERE bid = 33;
>> bench | pgbench | active | 00:31:35.234112 | UPDATE
>> pgbench_branches SET bbalance = bbalance + -713 WHERE bid = 38;
>> bench | pgbench | active | 00:31:34.434676 | UPDATE
>> pgbench_branches SET bbalance = bbalance + -921 WHERE bid = 33;
>> bench | psql | active | 00:00:00 | SELECT
>> datname,application_name,state,now()-xact_start AS wait,query FROM
>> pg_stat_activity ORDER BY wait DESC;
>> (10 rows)
>>
>> but no errors in the logs, any thoughts?
>

Can you get the call stacks?

>
>
> FWIW, retesting with the wal logging patch removed (i.e leaving the
> concurrent hast one) works fine.
>

Okay, information noted.

Thanks for testing and showing interest in the patch.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com