Re: Sudden insert performance degradation
| От | Henrique Montenegro |
|---|---|
| Тема | Re: Sudden insert performance degradation |
| Дата | |
| Msg-id | CAH_aqbuGg7QcRsWjs6fog20RqoF4XG6WdnH+BTp2dzhMUg-KSw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Sudden insert performance degradation (Sebastian Dressler <sebastian@swarm64.com>) |
| Ответы |
Re: Sudden insert performance degradation
(Sebastian Dressler <sebastian@swarm64.com>)
|
| Список | pgsql-performance |
On Mon, Jul 13, 2020 at 11:20 AM Sebastian Dressler <sebastian@swarm64.com> wrote:
Hi Henrique,On 13. Jul 2020, at 16:23, Henrique Montenegro <typoon@gmail.com> wrote:[...]
* Insert the data from the `users` table into the `users_no_dups` table
```
insert into users_no_dups (
created_ts,
user_id,
name,
url
) (
select
created_ts,
user_id,
name,
url
from
users
) on conflict do nothing
```How do you check contraints here? Is this enforced with UK/PK?
The Unique Key is supposed to to the constraint enforcing here. The `users` table will have data that is duplicate and the maximum number of records on it is 1 million. Then I just try to insert it into the `users_no_dups` table with the `on conflict do nothing` to ignore the duplicates and discard them.
Running the above loop worked fine for about 12 hours. Each file was taking
about 30 seconds to be processed. About 4 seconds to create the `users` table
and have the CSV data loaded into it and anything between 20 and 30 seconds to
insert the data from `users` into `users_no_dups`.Do you see anything suspicious in the logs, i.e. something in the realms of running out of transaction IDs?
I set the log to debug1. I haven't seen anything that called my attention, but I am not really sure what to look for, so perhaps I missed it. Any suggestions on what to look for or any specific log configuration to do?
[...]Recreating the table now isn't really providing any improvements. I tried
recreating it with a `fillfactor` of `10`, but it was taking too long and too
much space (the table had 300GB with the fillfactor set to 30; with it set to
10 it went up to almost 1TB).To me it sounds like the UK/PK is getting too much to write. A possible solution could be to start partitioning the table.
I thought about partitioning it, but I can't figure out on what. The `user_id` column is a number that is somewhat random so I don't know what kinds of range I would use for it. I will try to look at the values again and see if there is something that I could perhaps use as a range. Any other suggestions?
[...]
```
ssl = off
shared_buffers = 8GB
work_mem = 12GB
maintenance_work_mem = 12GB
max_stack_depth = 4MB
synchronous_commit = off
wal_writer_flush_after = 128MB
max_wal_size = 32GB
min_wal_size = 80MB
effective_cache_size = 96GB
```Another suggestion would be to increase the min_wal_size here, but since you use UNLOGGED tables it does not matter much.
Information about the machine:
```
Processor: 2x Intel(R) Xeon(R) CPU E5-2630L v2 @ 2.40GHz (6 cores each, 12 threads)
RAM: 256GB
Disk1: 2TB SSD SATA-3 Samsung Evo 860
Disk2: 6TB HDD SATA-3 Seagate Exos Enterprise 7200RPM
Disk3: 8TB HDD SATA-3 Seagate Exos Enterprise 7200RPM
Disk1 and Disk2 are configured as a single logical volume.Just curious: does that mean you mix up SSD + HDD?
Yeah, I did that. Probably not very smart of me. I plan on undoing it soon. I assumed that is not what is causing my issue since the tablespace where the table is stored is on `Disk3` which is not part of the Logical Volume.
Cheers,Sebastian--
Sebastian Dressler, Solution Architect
+49 30 994 0496 72 | sebastian@swarm64.com
Swarm64 AS
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Registered at Brønnøysundregistrene in Norway under Org.-Number 911 662 787
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Thanks!
Henrique
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