PgConf.Russia 2020

Examples of Sequences' opportunities implementations for developing business-logic powered by stored functions.

Everyone has heard something about transaction isolation levels, but oddly enough, almost no one can clearly explain what it is any why it is important. At the same time, for many operations, it is critical to have a clear understanding of isolation levels and how they can affect the result. Indeed, if a customer has been paid twice and the developer has to pay back the losses, it won't seem unimportant. We'll discuss how to avoid such unpleasant situations.

I will share our experience of migrating a server application for Russian railways from Oracle 11g Standard Edition to vanilla PostgreSQL 11.5.
At the time of migration, the database contained about 200 stored procedures of over 60000 lines of Oracle PL/SQL code (which has been developed since 2006, that is, for more than 12 years), about 250 tables, and 50GB of data.
Starting with a prologue, we'll describe our adventures along the migration process, as well as pleasant and unpleasant surprises we encountered, and finally get to an epilogue and a happy end. The story is told on behalf of an Oracle user exploring Postgres.

Today no one is surprised by cloud infrastructure anymore, but not all its components are easy to deploy in cloud. For example, the database is always very demanding in terms of performance and resources. Scaling and fault tolerance are the most acute problems, that's why we have been observing rapid development of alternative DBMS in the recent years. However, traditional relational DBMS have already accumulated a lot of various features, so they often remain the first choice. Besides, they are constantly evolving and offer a wide variety of scaling tools. I will mainly speak about PostgreSQL, when you should consider scaling, and how to do it right.

We will touch upon the following topics:
- Streaming replication and balancing read/write workloads
- Logical replication and data sharding
- High availability and fault tolerance

This talk should be interesting to DBAs, system administrators, team leads, infrastructure architects, as well as wider audience dealing with PostgreSQL.