PGConf.Russia 2022

Every DBMS stores its data on a hard disc, so you may face a situation when your data on disc gets corrupted. This can happen due to a controller failure, logical or physical data corruption; there are also other reasons. If it is just the index file that gets corrupted, the index recreation command will enable you to restore data consistency in your DBMS. If a table file or a file of a system section gets corrupted, data restore is impossible. In this case, you need to invent workarounds. You can try to restore this data from backup files, copy it from the corrupted table, or find another way to solve this problem. In this talk, we'll tackle several cases of data corruption on disc and describe the options for restoring the data from the corrupted tables.

Usage of temporary tables in PostgreSQL causes additional issues like high server resources consumption and low query performance. However, sometimes you need to rely on them especially when you need to migrate your code from MS SQL, and your initial code employed them, and you had some logic implemented at the database level. This talk covers issues related to usage of temporary tables when migrating from MS SQL, and the ways to resolve them using built-in PostgreSQL features based on the scenarios contained in the code.

We'll talk about the ways to change the database records without updates. To do this, we'll explore what's going on at the lowest level and see what can happen if we make changes in data files in different operation modes.

My talk covers PostgreSQL infrastructure in Ozon: - how do we tune virtual machines (KVM); - which version control system we have created; - which drivers we make and how it relates to fault tolerance and load balancing; - how do we make "hot" upgrades for the parameters of our virtual machines.