Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Overview of this book

PostgreSQL is a powerful opensource database management system; now recognized as the expert's choice for a wide range of applications, it has an enviable reputation for performance and stability. PostgreSQL provides an integrated feature set comprising relational database features, object-relational, text search, Geographical Info Systems, analytical tools for big data and JSON/XML document management. Starting with short and simple recipes, you will soon dive into core features, such as configuration, server control, tables, and data. You will tackle a variety of problems a database administrator usually encounters, from creating tables to managing views, from improving performance to securing your database, and from using monitoring tools to using storage engines. Recipes based on important topics such as high availability, concurrency, replication, backup and recovery, as well as diagnostics and troubleshooting are also given special importance. By the end of this book, you will have all the knowledge you need to run, manage, and maintain PostgreSQL efficiently.
Table of Contents (13 chapters)

Detecting an in-doubt prepared transaction

While using two-phase commit (2PC), you may end up in a situation where you have something locked but cannot find a backend that holds the locks. This recipe describes how to detect such a case.

How to do it...

You need to look up the pg_locks table for those entries with an empty pid value. Run this query:

SELECT t.schemaname || '.' || t.relname AS tablename,
l.pid, l.granted
FROM pg_locks l JOIN pg_stat_user_tables t
ON l.relation = t.relid;

The output will be something similar to the following:

tablename | pid | granted

-----------+-------+---------
db.x | | t
db.x | 27289 | f
(2 rows)

The preceding example shows a lock on the db.x...