How do we Troubleshoot PostgreSQL Contention in MinervaDB?

In PostgreSQL, the catalog tables are system tables that store metadata information about the database objects such as tables, indexes, functions, and users. The catalog tables can be used to troubleshoot contention issues by providing information about the current state of the database and the resources being used by different sessions.

Here are some of the catalog tables that can be useful for troubleshooting contention in PostgreSQL:

  1. pg_locks: This catalog table shows the current locks held by sessions in the database. It includes information such as the lock type, mode, and object being locked. By querying this table, you can identify which sessions are holding locks and which sessions are waiting for locks to be released.
  2. pg_stat_activity: This catalog table shows the current activity of sessions in the database. It includes information such as the query being executed, the state of the session, and the user connected to the session. By querying this table, you can identify which sessions are causing contention by holding locks or executing long-running queries.
  3. pg_stat_user_tables: This catalog table shows statistics about table access patterns, including the number of sequential and index scans, the number of tuples read and written, and the number of dead tuples. By querying this table, you can identify which tables are being accessed frequently and which tables may be causing contention due to excessive table scans or updates.
  4. pg_stat_user_indexes: This catalog table shows statistics about index usage, including the number of index scans and the number of index entries read and written. By querying this table, you can identify which indexes are being used frequently and which indexes may be causing contention due to excessive index scans.
  5. pg_stat_replication: This catalog table shows statistics about replication activity in a streaming replication setup. It includes information such as the current position of the standby server, the number of bytes sent and received, and the lag time between the primary and standby servers. By querying this table, you can identify replication issues that may be causing contention, such as a slow network connection or a lagging standby server.

SQL Script we use for monitoring PostgreSQL contention:

Conclusion

These catalog tables can be queried using SQL statements to provide insights into the current state of the database and to troubleshoot contention issues. By analyzing the information in these tables, you can identify the source of contention and take appropriate actions to resolve the issue.

About Shiv Iyer 443 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.