Re: Write Ahead Logging for Hash Indexes

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?

Cheers

Mark