Re: Write Ahead Logging for Hash Indexes - Mailing list pgsql-hackers

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.