Afaict nothing in this benchmark will actually use AIO in 18. As of 18 there is aio reads for seq scans, bitmap scans, vacuum, and a few other utility commands. But the queries being run should normally be planned as index range scans. We're hoping to the the work for using AIO for index scans into 19, but it could work end up in 20, it's nontrivial.
It's also worth noting that the default for data checksums has changed, with some overhead due to that.
If the benchmark doesn’t use AIO, why the performance difference between PG 17 and 18 in the blog post (sync, worker, and io_uring)?
Is it because remote storage in the cloud always introduces some variance & the benchmark just picks that up?
For reference, anarazel had a presentation at pgconf.eu yesterday about AIO. anarazel mentioned that remote cloud storage always introduced variance making the benchmark results hard to interpret. His solution was to introduce synthetic latency on local NVMes for benchmarks.
I was expecting `pg_dumpall` to get the `--format` option in v18,[0] but at the moment the docs say it's still only available in the development branch.[1]
Is anyone familiar with Postgres development able to give an update on the state of the feature? Is it planned for a future (18 or 19) release?
If you care about performance, don't use network storage.
If you are using local nvme disk, then it does not matter if you are using Postgres 17 or 18. Performance is about the same. And significantly faster than network storage.
just for reference with 4 consumer nvmes and raid10 and pciex16 you can easily do 3m IOPS for one time cost of like 1000$
in my current job we constantly have to rethink db queries/design because of cloud IOPS, and of course not having control over RDS page cache and numa.
every time I am woken up at night because a seemingly normal query all of the sudden goes beyond our IOPS budget and the WAL starts trashing, I seriously question my choices.
Where are the error bars? I don’t get why people run all these tests and don’t give me an idea of standard deviation or whether the differences are actually statistically significant.
I'm currently running PostgreSQL in docker containers using bitnami/postgresql:17.6.0-debian-12-r4. As I understand it, Bitnami is no longer supporting or updating their Docker containers. Any recommendations on a upgrade path to PostgreSQL 18 in Docker?
A quick glance of swapping to the official postgres container shows POSTGRESQL_DATABASE is renamed to POSTGRESQL_DB. The other issue is the volume mount path is currently /bitnami/postgresql.
I'm literally in the middle of upgrading my prod db to pg18. Its about 6tb, has a few thousand queries per second, should I be considering running in 'worker' mode instead of 'io_uring'?
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[ 2.4 ms ] story [ 31.8 ms ] threadI concluded that better IO planning it's only worth it for "slow" I/O in 18.
Pretty sure it will bring a lot of learnings. Postgress devs are pretty awesome.
It's also worth noting that the default for data checksums has changed, with some overhead due to that.
Is it because remote storage in the cloud always introduces some variance & the benchmark just picks that up?
For reference, anarazel had a presentation at pgconf.eu yesterday about AIO. anarazel mentioned that remote cloud storage always introduced variance making the benchmark results hard to interpret. His solution was to introduce synthetic latency on local NVMes for benchmarks.
Has anybody seriously benchmarked this ?
I don’t think io uring would make a difference with this setting but I’m curious, as it’s the default for oracle and sybase.
Is anyone familiar with Postgres development able to give an update on the state of the feature? Is it planned for a future (18 or 19) release?
[0]: https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit...
[1]: https://www.postgresql.org/docs/devel/app-pgdump.html#:~:tex...
If you care about performance, don't use network storage.
If you are using local nvme disk, then it does not matter if you are using Postgres 17 or 18. Performance is about the same. And significantly faster than network storage.
just for reference with 4 consumer nvmes and raid10 and pciex16 you can easily do 3m IOPS for one time cost of like 1000$
in my current job we constantly have to rethink db queries/design because of cloud IOPS, and of course not having control over RDS page cache and numa.
every time I am woken up at night because a seemingly normal query all of the sudden goes beyond our IOPS budget and the WAL starts trashing, I seriously question my choices.
the whole cloud situation is just ridiculous.
A quick glance of swapping to the official postgres container shows POSTGRESQL_DATABASE is renamed to POSTGRESQL_DB. The other issue is the volume mount path is currently /bitnami/postgresql.