PGConf.Russia 2022

Previously, we have explained the internals of Avito, discussed, where and how we store your classifieds, and how they appear on the search results. In the recent 3-4 a lot has changed in Avito. We got rid of logical replication, stopped using standby servers for reads, removed nearly all stored procedures and our custom failover solution, migrated all our classifieds into a sharded DBMS, switched from the monolith app to microservices. I'll explain why we made such decisions, list some of the problems we encountered and describe the current state of our development process.

PostgreSQL has a number of peculiarities that you need to take into account not only while maintaining your database but also when designing your database schema. Experienced PostgreSQL are well aware of vacuuming process. On the web one can find tons of materials covering its internals, configurations and monitoring. Many valuable talks about vacuum were given at numerous conferences. However, we still face the common wraparound problem when the maximum possible number of transactions (xid) is reached. It happens even on databases that are relatively small in size. In my presentation, I will share a customer case that looks interesting to me. A chain of mistakes made at different stages of the database's life cycle once caused a disaster. The database fully stopped for one week, we detected a wraparound and spotted corrupted blocks. Maintenance was problematical, and we spent sleepless nights in search of a solution. We managed to achieve a local win as we finally restored the database, but it's not the end of this story, which makes it even more interesting.

The release cycle for version 15 is nearing completion. At the time of the presentation, the complete list of changes will not be known. But for sure there will be something to talk about.

The plv8 extension is very underestimated, though it can help simplify development for a variety of tasks. It's been a year since we started using this extension in our projects. The main reason for its low popularity is the complexity of building. Moreover, building plv8 requires a lot of traffic and disc space for temporary files. That's why we decided to build plv8 and provide ready-made binaries freely to anyone interested, not just as an offering for our customers. First, we made the binaries available on GitHub. Then we created a Docker image for Postgres with pre-installed plv8 based on Debian. It looked too heavy to us, and we decided to check Alpine, however, building it for Alpine appeared to be more complicated than we expected. I'll explain what difficulties we faced and how we managed to overcome them. I will also list the tasks that can be solved with plv8 and provide advice on how to make the development process more convenient. I will also share the links to our Docker images for the latest Postgres 13 and Postgres 14 releases, that are compact and can be used for any types of tasks.