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This Week in PostgreSQL – May 31

Since last October I’ve been periodically writing up summaries of interesting content I see on the internet related to PostgreSQL (generally blog posts). My original motivation was just to learn more about PostgreSQL – but I’ve started sharing them with a few colleagues and received positive feedback.  Thought I’d try posting one of these digests here on the Ardent blog – who knows, maybe a few old readers will find it interesting? Here’s the update that I put together last week – let me know what you think!


Hello from California!

Part of my team is here in Palo Alto and I’m visiting for a few days this week. You know… for all the remote work I’ve done over the years, I still really value this in-person, face-to-face time. These little trips from Seattle to other locations where my teammates physically sit are important to me.

This is also part of the reason I enjoy user groups and conferences so much. They’re opportunities to meet with other PostgreSQL users in real life. In fact – at this very moment – one of the most important PostgreSQL conferences in the world is happening: PgCon! Having attended a few other conferences over the past year, I’m holding down the fort in the office this week in order to send a bunch of other teammates… but you can be sure I’m keeping an eye on twitter. :)

https://www.pgcon.org/2018/
https://twitter.com/search?l=&q=pgcon%20OR%20pgcon_org

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In the meantime, lets get busy with the latest updates from the postgresql virtual world. First of all, I think the biggest headline is that (just in time for pgcon) we have the first official beta version of PostgreSQL 11! The release announcement headlines with major partitioning enhancements, more parallelism, a feature to speed up SQL execution by compiling certain operations on-demand into native machine code (JIT/Just-In-Time compilation), and numerous SQL enhancements. You can also read the first draft of the release notes. This is the time to start testing and give feedback to the development community!

https://www.postgresql.org/about/news/1855/
https://www.postgresql.org/docs/devel/static/release-11.html

Closely related to this, there’s one other really big headline that I’m excited about: the new AWS RDS Preview Environment. You can now try out the new pg11 features ahead of time with a single click! In part because the development community is so awesome, the first database available in the RDS Preview Environment is PostgreSQL. And the official PostgreSQL 11 beta release is _already_ available on RDS!! Personally I’m hoping that this benefits the community by getting more people to test and give feedback on new features being built for PostgreSQL 11. I hope it will make a great database even better.

https://aws.amazon.com/rds/databasepreview/
https://forums.aws.amazon.com/ann.jspa?annID=5788 (pg11 beta announcement)

Outside of the RDS and PG11-related stuff, I saw one other headline that I thought might be worth mentioning. On May 29, IBM published a blog post that caught my attention, featuring EnterpriseDB as an IBM partner on their Private Cloud deployments. You might not realize just how much PostgreSQL is being used and sold by IBM… but there’s Compose, ElephantSQL, and now EDB in the mix.

https://www.ibm.com/blogs/think/2018/05/next-enterprise-platform/

Part of the reason I took note of this was that I remember just last November when HPE ran a similar announcement, partnering with EDB on their on-premise subscription-based GreenLake platform.

https://news.hpe.com/hpe-expands-pay-per-use-it-to-key-business-workloads/

So it seems to me that EDB is doing some nice work at building up the PostgreSQL presence in the enterprise world – which I’m very happy to see. To be clear, this isn’t necessarily new… does anyone remember vPostgres?

https://blogs.vmware.com/vsphere/2016/03/getting-comfortable-with-vpostgres-and-the-vcenter-server-appliance-part-1.html

Nonetheless, it feels to me like the ball is moving forward. It feels like PostgreSQL maturity and adoption are continually progressing at a very healthy pace.

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Moving on from headlines, lets get to the real stuff – the meaty technical articles. :)

First up, who likes testing and benchmarking? One of my favorite activities, truth be told! So I can’t quite convey just how excited I am about the preview release of Kevin Closson’s pgio testing kit. For those unfamiliar, Kevin has spent years refining his approach for testing storage through database I/O paths. Much work was done in the past with Oracle databases, and he calls his method SLOB. I’m excited to start using this kit for exploring the limits of storage through PostgreSQL I/O paths too.

https://kevinclosson.net/2018/05/23/sneak-preview-of-pgio-the-slob-method-for-postgresql-part-iv-how-to-reduce-the-amount-of-memory-in-the-linux-page-cache-for-testing-purposes/

Right after Kevin published that post, Franck Pachot followed up with a short article using pgio to look at the impact of the ext4 “sync” filesystem option (made relevant by the recently disclosed flaws in how PostgreSQL has been interacting with Linux’s implementation of fsync).

https://blog.dbi-services.com/postgres-the-fsync-issue-and-pgio-the-slob-method-for-postgresql/

In addition to Kevin’s release of PGIO, I also saw three other generally fun technical articles. First, Kaarel Moppel from Cybertec published an article showing much lower-than-expected impact of pl/pgsql triggers on a simple pgbench execution. Admittedly, I want to poke around at this myself, having seen a few situations myself where the impact seemed higher. Great article – and it certainly got some circulation on twitter.

https://www.cybertec-postgresql.com/en/are-triggers-really-that-slow-in-postgres/

Next, Sebastian Insausti has published an article explaining PostgreSQL streaming replication. What I appreciate the most about this article is how Sebastian walks through the history of how streaming replication was developed. That context is so important and helpful!

https://severalnines.com/blog/postgresql-streaming-replication-deep-dive

Finally, the requisite Vacuum post.  :)  This month we’ve got a nice technical article from Sourabh Ghorpade on the Gojek engineering team. Great high-level introduction to vacuuming in general, and a good story about how their team narrowly averted an “xid wraparound” crisis.

https://blog.gojekengineering.com/postgres-autovacuum-tuning-394bb99fe2c0

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We’ve been following Dimitri Fontaine’s series on PostgreSQL data types. Well sadly (but inevitably) he has brought the series to a close. On May 24, Dimitri published a great summary of the whole data type series – this definitely deserves to be on every developer’s short list of PostgreSQL bookmarks!

https://tapoueh.org/blog/2018/05/postgresql-data-types/

But while we’re talking about data types, there were two more related articles worth pointing out this time around. First, Berend Tober from SeveralNines published a nice article back on the 9th about the serial data type in PostgreSQL. This is an integer type that automatically comes with not-null constraints and auto-assignment from a sequence.

https://severalnines.com/blog/overview-serial-pseudo-datatype-postgresql

Secondly, Hans-Jürgen Schönig from Cybertec gives a nice overview of mapping data types from Oracle to PosgreSQL. He has a little paragraph in there about mapping Oracle numbers to PostgreSQL integers and numerics. That little paragraph probably deserves triple-bold-emphesis. Automatic mapping of every number column to PostgreSQL numeric has been cause for many, many performance woes in PostgreSQL databases!

https://www.cybertec-postgresql.com/en/mapping-oracle-datatypes-to-postgresql/

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For something that might be relevant to both developers and DBAs, I have a couple articles about SQL tuning. First, Brian Fehrle has written a great tuning introduction for the severalnines blog. His starting point is pg_stat_activity and the explain SQL command; exactly the same as my starting point. :)

https://severalnines.com/blog/why-postgresql-running-slow-tips-tricks-get-source

Next up, Louise Grandjonc from France has published a series of articles called “understanding EXPLAIN“. Did you ever wonder why there are _two_ numbers reported for execution time of each step? Louise answers this question and many more in the these four articles!

http://www.louisemeta.com/blog/explain/
http://www.louisemeta.com/blog/explain-2/
http://www.louisemeta.com/blog/explain-3/
http://www.louisemeta.com/blog/explain-4/

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Moving down the stack a little more, there were two articles about monitoring that seem worth passing along. Datadog has put out a lot of articles about monitoring recently. I hadn’t mentioned it before, but Emily Chang gave us yet another one back on April 12. As usual, I’m impressed with the level of quality in this thorough article which is specifically focused on PostgreSQL on RDS. I especially appreciated the key metrics, things I’ve used myself to characterize workloads.

https://www.datadoghq.com/blog/aws-rds-postgresql-monitoring/

Earlier I mentioned the severalnines blog post about replication – and the pgDash team published a nice article on May 2 about monitoring replication. The give another nice general architectural overview of replication as well.

https://pgdash.io/blog/monitoring-postgres-replication.html

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In my last update, I closed with a few articles about pgpool on the severalnines blog. It seemed worth mentioning that they have published a third, final article for their series.

https://severalnines.com/blog/guide-pgpool-part-three-hints-observations

Also, I spotted an article about pgpool on the AWS database blog too. While focused on Aurora PostgreSQL, there’s plenty to be learned about using pgpool with regular PostgreSQL here.

https://aws.amazon.com/blogs/database/a-single-pgpool-endpoint-for-reads-and-writes-with-amazon-aurora-postgresql/

Along those lines, most people know about the other popular PostgreSQL connection pooler, pgbouncer. This is the connection pooler which is used by Gulcin Yildirim’s near-zero-downtime ansible-based upgrade tool, pglupgrade. He’s written a few articles about his process recently, and being a big ansible fan I’ve been following along.

https://blog.2ndquadrant.com/near-zero-downtime-automated-upgrades-postgresql-clusters-cloud/
https://blog.2ndquadrant.com/near-zero-downtime-automated-upgrades-postgresql-clusters-cloud-part-ii/

But I wonder if the landscape is about to change? Yesterday the Yandex team announced that they have built and released a new load balancer to address limitations in pgpool and pgbouncer. I’ll be very interested to see what happens with odyssey!

https://www.postgresql.org/message-id/C9D1137E-F2A7-4307-B758-E5ED5559FFCA@simply.name (announcement)
https://github.com/yandex/odyssey

And that wraps things up for this edition.

Have a great week and keep learning!