Philip McClarence

What does “ERROR: syntax error at or near “identifier”” mean and how do you diagnose and fix it?

05/01/2024 by Philip

The error message ERROR: syntax error at or near “identifier” in PostgreSQL indicates that there is a syntax mistake in the SQL query near the specified “identifier”. The term “identifier” in the error message will be replaced by the specific keyword, operator, or name that PostgreSQL has identified as being incorrectly used or placed in …

How to migrate RDS Postgres to AWS Aurora without downtime?

04/01/2024 by Philip

Migrating from RDS Postgres to AWS Aurora without downtime can be achieved by using Amazon’s Database Migration Service (AWS DMS) along with additional strategies for minimizing the impact on production systems. Here’s a general outline of the steps you would take: For detailed instructions and considerations, you can refer to the AWS documentation on migrating data …

How to Troubleshoot “ERROR: Could Not Serialize Access Due to Concurrent Update” in PostgreSQL: Expert Solutions for Database Conflicts

04/01/2024 by Philip

When handling databases in PostgreSQL, encountering errors related to concurrent updates is not uncommon. These errors often manifest as ‘ERROR: could not serialize access due to concurrent update’, which can be perplexing and halt the workflow. Understanding the dynamics of PostgreSQL’s transaction mechanisms is crucial to diagnose and resolve such issues effectively. Dealing with the …

How do you identify high load tables/indexes in Postgres

11/12/2022 by Philip

To identify high-load tables or indexes in Postgres, you can use the pg_stat_all_tables or pg_stat_all_indexes views. These views provide information about the access statistics for each table and index in a database. To access these views, you can connect to your Postgres database using a tool like psql and then run a query like the …

How can I secure a Postgres Database

11/12/2022 by Philip

There are several steps you can take to secure a Postgres database. Here are a few:

Use a strong password for the database administrator account to prevent unauthorized access.

Enable SSL connections to encrypt data transmitted between the database server and client applications.
Configure your database server to listen on a private network interface or localhost, instead of all interfaces. This will prevent remote connections to the database server.
Use the built-in Postgres role-based access control (RBAC) system to grant specific users access to specific database objects and operations.

Regularly back up your database to protect against data loss and enable recovery in case of a disaster.
Use Postgres’ built-in auditing capabilities to track and log access to the database, so you can monitor for suspicious activity and quickly identify and respond to security threats.
Keep your Postgres installation and all database extensions up to date with the latest security patches to protect against known vulnerabilities.

All about Logical Replication in Postgres.

04/01/202406/12/2022 by Philip

What is Logical Replication

Logical replication in PostgreSQL is a feature that allows you to replicate data from one database to another, in a flexible and customizable way. Unlike physical replication, which replicates the entire database and its structure, logical replication allows you to specify which tables and columns you want to replicate, and how you want the data to be replicated. This means that you can replicate only the data that is relevant to your application, and you can apply custom transformations or filters to the replicated data to meet your specific needs.

When and How do you use pg_rewind() in PostgreSQL?

06/12/2022 by Philip

The pg_rewind utility in PostgreSQL is used to synchronize a standby server with a new master server in a scenario where the old master server has been promoted to a new master server and the standby server needs to catch up with the new master server’s state. This utility can be used when the old master server still has the transaction logs (WAL) that were generated after the promotion, and it can be used to “rewind” the state of the standby server to the point in time where the promotion occurred.

To use the pg_rewind utility, you need to perform the following steps:

How do I Re-Attach a Master once a Replica has been Promoted in Postgres

06/12/2022 by Philip

To reattach a master server once a replica has been promoted in PostgreSQL, you need to perform the following steps:

On the new master server, edit the postgresql.conf configuration file and set the wal_level parameter to hot_standby. This will enable the new master server to keep a sufficient amount of transaction log data (WAL) to allow the old master server to connect and apply the changes.
Restart the new master server for the changes to take effect.

On the old master server, edit the postgresql.conf configuration file and set the hot_standby parameter to on. This will enable the old master server to connect to the new master server and start receiving the changes.
In the recovery.conf file on the old master server, add the following lines to specify the connection details for the new master server:

PostgreSQL – How to Create Database

06/12/2022 by Philip

To create a new database in PostgreSQL, you can use the CREATE DATABASE statement. Here is the basic syntax for this statement: Replace database_name with the name of the database that you want to create. For example, to create a database named my_database, you would use the following statement: This will create a new database …

How do you promote a replica in Postgres?

06/12/2022 by Philip

To promote a replica in PostgreSQL, you need to perform the following steps:

On the standby server, shut down the PostgreSQL service using the appropriate command for your operating system. For example, on Linux you can use the systemctl command like this:

sudo systemctl stop postgresql