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Hi everyone, today we're going to talk a little bit about Postgres.
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Quick show of hands: who already uses Postgres? Awesome! And who does not? Alright, if you're too shy, we can chat afterwards. I'm happy to convince you.
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I take the exact opposite of the philosophy that says the database is a dumb hashing tool. We will get into why I think it’s important to know a little about your database to work better with it and to handle it at pretty much any scale without having to go back to school and take a bunch of database courses.
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This is really a 101 session with a lot of links and references to help you treat it a little better. First, a little bit about me: I was one of the first product managers at Roku and spent about five and a half years there, primarily building and running Heroku Postgres.
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We ran around 1.5 million Postgres databases across a team of about eight of us, which I think is a pretty good ratio of databases to engineers for such a large site.
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I will talk a little bit more about the site later, but the short story is that we turned Postgres into a distributed database, and it is transparent to your application.
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We were at Clara right about a year ago, and now I'm at Microsoft. If you like Postgres and want to learn a bit more about it, I create a newsletter called Postgres Weekly, which is highly curated.
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It sounds like Ruby Weekly and others, but it doesn't include a hundred items; it’s more about the top 10, 15, or 20 items that are really targeted toward application developers, not just the DBA crowd.
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Based on the show of hands in this room, I think everyone's hand went up. Postgres is more popular than ever; it’s kind of the largest open-source database and is growing in popularity.
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If you look at sites like Hacker News and see who’s hiring, I don't know if you count that as a barometer of success, but Postgres ranks number one among databases.
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It's really well-loved and well-liked as a relational database. First, this is a really fun excerpt from the Postgres mailing list from 2006 about Tom Lane.
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Anyone know who he is? For those who don’t, Tom Lane helped create TIF, was on the board for creating the spec for JPEG, co-authored the JPEG spec, and then co-authored the PNG spec.
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He got tired of working with images and decided to work with databases instead. He has been working with Postgres for about the last 15 to 20 years and is the primary contributor to much of Postgres.
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He is among the top five or so open-source contributors. This was him, 14 years ago on the mailing list, coming back from a conference, stating that the biggest mistake Postgres ever made was its name.
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He argued that it is not Postgres SQL; it’s okay to just call it Postgres. It’s painful to this day, and I’m actually thinking of starting a campaign with all the core developers to call it Postgres to annoy them until they change it.
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If you're new to Postgres or someone asks you why you like it, I think many of us engineers often jump onto a bandwagon and say, \'Oh, it's cool, of course I’m using it.\' But when asked why, we may not provide a good answer.
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It’s a really feature-rich database. For instance, data types are something to consider. I’m genuinely excited about this. You wouldn’t think that it stands out in terms of a database, but it’s quite useful.
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Postgres supports powerful transactional DDL. If you’re running a migration and it fails, you can actually roll it back and not end up in a mid-migration mess.
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Foreign data wrappers allow you to connect from inside Postgres to another database and query directly. So, if you have stuff in Redis and want to interact with it in Postgres, you can query directly from those other databases.
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The Listen/Notify feature provides pub/sub directly inside your database. Some of these features will not be covered in detail in this talk, but if you’re curious about them, I’m happy to chat afterwards or you can look them up.
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Now, let’s delve into some background on Postgres. It's unique as an open-source database. Within Rails, there is no single owner; it’s based on a very liberal license which is rare for databases.
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You can take it, modify it, and resell it. This happens frequently; for example, Greenplum, Redshift, Aster Data, and others were all originally based on Postgres. They took it, modified it, and now don’t look much like Postgres anymore.
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Postgres has gained popularity in academia because you can create PhD projects on it, ship them, change them, and do whatever you want with it.
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The community is interesting; there’s a core team that acts like a steering committee with a committer base of about 40 people who are committed to Postgres. This number has actually doubled over the last three years.
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There are major contributors and minor contributors, so you can contribute significantly to Postgres without necessarily becoming a committer.
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Discussions and patches get handled through mailing lists. There’s no central Git repository or pull request model; it has functioned like this for the past 20 years.
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If you want to learn more about Postgres, the PG User mailing list is a good place to start. If you want to deep dive into Postgres, the core hackers list is where they discuss deep kernel issues.
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It is fascinating, though I don’t understand half of what they discuss there. If you want to level up, it's a great place to go and subscribe.
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Postgres regularly releases updates, usually every fall. Previously, major releases had decimal point versions—9.2, 9.4, etc. Now, major versions are numbered without decimals, such as 10, 11, 12.
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Minor versions are released with security fixes or patches, typically about once a month. They used to have marquee features, like JSON support, but it’s evolved.
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In version 9.4, JSONB (Binary JSON) was introduced, allowing better storage and indexing, which is extremely powerful.
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Let’s discuss more features and why Postgres stands out. One of its strengths is its liberal approach to new data types. There are around 180 types supported.
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For instance, if your application is using arrays, you can compactly store data in arrays in the database instead of joining them to another table.
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Data types such as JSON and JSONB are highly useful. JSON is better for preserving whitespace in API data logs, while JSONB is better for querying.
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Working with time zones is made easier with Postgres, as it can automatically shift time zones.
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Timestamp is an incredibly useful data type in Postgres. UUIDs are handy if you’re using them in your app and can be directly stored in the database.
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Range types are beneficial if you’re developing applications that need to manage range constraints, like calendar applications where overlapping classes shouldn't occur.
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SQL support in Postgres is feature-rich, including common table expressions (CTEs) known as \'with\' clauses. Who enjoys writing SQL?
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Hands? More hands for reading SQL. SQL is a powerful language, but with CTEs, your queries can be more readable and maintainable.
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Window functions are very useful for tasks like ranking based on categories. Postgres has many built-in functions for data manipulation.
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Regarding indexing, if you're like me and don’t have a CS degree, navigating through different index types can be daunting.
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In general, B-tree is a commonly used index type, and with each major Postgres release, new index types are introduced.
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There’s a group in the community that works on about index types, finding uses for specific data structures. For example, GIN (Generalized Inverted Index) is great for JSONB.
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Full-text search and geospatial indexing are also prominent features of Postgres, allowing complex data interactions like overlapping text or polygons.
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When dealing with spatial data, I often hear that Postgres is great for working with large datasets of information that cluster together.
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When creating procedural SQL, there is PL/pgSQL, and the option to use PL/v8, which incorporates the full v8 JavaScript engine directly into Postgres.
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This means you can write JavaScript within the database, opening up new capabilities and making complex logic easier to implement in your application.
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Postgres is also becoming a data platform, moving away from being just a strict relational database. It is slow and stable but unique with its extension framework.
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You can add low-level hooks to change Postgres behavior, create new data types, or even new indexes. One notable extension is PostGIS.
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PostGIS is widely regarded as the advanced open-source geospatial database, which hooks into Postgres, extending it with new data types and functions.
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If you are looking for time series capabilities, there are several extensions that support this as well. If you need to migrate from Oracle to Postgres, there’s an extension to help with compatibility.
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The ability to extend Postgres allows you to make extensive changes without waiting for a new core release. There are about 100 extensions available now.
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For pro tips, if you use terminal interfaces, PSQL is really good. How many of you have configured your .bashrc?
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Most hands. How many of you have a PSQL config? Anyone?
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PSQL is powerful enough to do things like auto-format your text, keeping it wrapped within your screen’s width, and address query timing for performance tracking.
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If you're ever asked to generate a report and need to retrieve the query from history, PSQL saves the history of every query run against your database.
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If the query is complex, you can save it and execute it later. This feature is especially handy when re-running past reports.
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If there are common queries you often write, you can name them so that executing them is as easy as just typing their name.
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If you’re not a CI person, another data tool to consider is pgAdmin, which provides a GUI interface for Postgres.
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Hopefully, by now, you’re convinced about using Postgres. If not, I encourage you to check out some articles I’ve shared.
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This talk has largely been about managing Postgres at various scales. To start, small databases—less than 10 gigabytes—are easy to handle with Postgres.
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You can leverage its data types, use arrays, timestamp data types, and JSONB effectively. Start putting indexes in place early.
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Make sure to have a backup strategy—if you haven’t tested your backups in six months, it’s wise to do so.
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Spend some time setting up your environment with PSQL and other tools. This will alleviate crisis situations when you are triaging unexpected problems.
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When you reach a medium scale—beyond 200 gigs to a terabyte scale—you’ll want to track performance closely. Key metrics to monitor include your cache hit ratio.
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You should aim for a cache hit ratio of 99% or higher. If it drops below 99%, you may need to analyze your indexing.
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Also, track your index hit ratio. When you issue a query, you don’t want Postgres scanning every single row.
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Leverage indexes for your most popular queries. This leads to better performance when you analyze the number of rows in each table.
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Sometimes you may need to drop unused indexes. It helps to periodically review the indexes and drop those that haven’t been used recently.
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Index management is crucial to optimizing your database’s performance and keeping it robust.
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Connections in Postgres can be a sore spot. Each new connection incurs some time overhead due to TLS negotiation; I estimate this takes about 50 milliseconds.
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Creating a pool with Active Record can lead to resource wastage if many idle connections accumulate, especially with high connection volumes.
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PG Bouncer is a great solution you can implement to optimize this situation. It helps manage connections more effectively by closing idle connections.
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If you are running a sizable workload, I would highly recommend using PG Bouncer.
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Now, as we delve deeper into the medium scale, focus on practical database needs—adding indexes, monitoring your cache ratios, and adjusting memory as needed.
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If you want to optimize specific queries, use tools like PG Stat Statements to review every query that has been run against your database.
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PG Stat Statements shows how many times each query was executed and the average and total time taken, allowing you to identify slower queries.
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If you’re above 50 to 100 gigs, consider shifting your backup strategy to encompass physical backups.
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Most people do a PG dump once a day; this is effective for logical backups.
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However, as you grow, you may want to adopt a physical backup strategy, such as using PG Backrest for efficient growth.
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As your database grows larger, think about sharding strategies to manage data effectively. Sharding allows splitting a large database into manageable bits.
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Citus is an extension that can help you turn multiple Postgres databases into a distributed setup.
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Ensure to hash your data upfront so you correctly distribute workloads across your shards based on customer IDs or other hashable identifiers.
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This approach will help keep data organized and ensure that your queries remain efficient as your application scales.
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Managing relational databases can be challenging due to multiple relationships and models, but there's a way to simplify the architecture.
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Grouping related data is essential; consider colocating your tables to help ensure transactional consistency without excessive overhead.
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You wouldn’t want to rely on a reference table with vast amounts of records, as it complicates the writing process across multiple nodes.
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In terms of collocation, keep your tables tightly linked through keys, which can yield better performance and less friction when querying the data.
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Monitor for N+1 queries that can deplete your cache hit ratio, leading to performance issues.
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Look for opportunities to offload workloads to read replicas for reporting and analytics that can tolerate slight lags.
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Ultimately, if sharding is necessary, look into modern practices as the landscape of distributed databases has evolved.
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Lessons can be learned from successful implementations, like Instagram, to manage scaling issues effectively.
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In summary, for small- to medium-sized databases, keep a close eye on your cache hit ratios, use proper indexing, and test your backups regularly.
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Monitoring connection limits with PG Bouncer can alleviate many performance issues.
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For larger scales, refine your backup strategy, select the right sharding model proactively, and ensure column colocations are effectively laid out.
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This proactive management approach can ensure that your applications remain robust and responsive as they scale.
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Thank you for your time!
