Re: Write Ahead Logging for Hash Indexes

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?

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