PgConf.Russia 2017

< Query failed: ERROR: deadlock detected
< DETAIL: Process 17371 waits for ShareLock on transaction 102733872; Blocked by process.
< Process 10414 waits for ShareLock on transaction 102733874; Blocked by process 17371.

Such "unpleasant" messages from the server can seriously puzzle the developer. When working with locks, in particular, with transactions in general, it is necessary to take into account the features of the implementation of client libraries, which can cause the above exception.

In the short talk, the mechanics of the interaction of locks will be explained, main attention being paid to causes of deadlocks. References to the relevant documentation pages will be given. A technique of "bypassing" this problem of concurrent data access will be described and illustrated with some generalized examples from practice are shown. The talk will be interesting to database developers and administrators as well as the client-side application developers.

MongoDB is a successful database in the NoSQL space, mostly used for OLTP-type workloads. However, due to the lack of ACID (transactions in particular) and significant performance issues with OLAP/DW workloads, more and more MongoDB users are considering migrating off of MongoDB to a RDBMS, where PostgreSQL is the usual choice. This represents a significant opportunity for the PostgreSQL ecosystem, to "bring NoSQL to SQL". This talk will present the challenges that MongoDB users are facing and the state of the art of the available tools and open source solutions available to perform ETL and live migrations to PostgreSQL. In particular, ToroDB Stampede will be discussed, an open source solution that replicates live from MongoDB, transform JSON documents into relational tables, and stores the data in PostgreSQL.

VIDEO

I love complex knowledge domains, strong typing in applications, and 3NF, but I hate ORM. That is why I’ve been actively storing serialized structures in JSON fields (even before the JSON type was introduced). In this talk, I will tell you about some specifics of storing complex structures within DBMS fields, what problems can arise, and how to cushion the blow.

VIDEO