How to fix "Error: the locale requested by the environment is invalid" during postgresql cluster upgrade (pg_upgradecluster)

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07-10-2024

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"Error: the locale requested by the environment is invalid" during PostgreSQL Cluster Upgrade: A Solution

Problem: You're attempting to upgrade your PostgreSQL cluster using pg_upgradecluster, and you encounter the dreaded error: "Error: the locale requested by the environment is invalid". This can be frustrating, especially when you're trying to move your database to a new version.

Rephrasing the Problem: In essence, your PostgreSQL cluster is saying it can't understand the language settings (like the language for dates, numbers, and currency) provided by your system. This often occurs during upgrades when there's a mismatch between the locales of your old and new PostgreSQL versions.

Scenario and Original Code:

Let's assume you're upgrading a PostgreSQL 12 cluster to PostgreSQL 15. The command you might be using is:

sudo pg_upgradecluster 12/main 15/main -d /path/to/datadir

And you receive the error:

ERROR:  the locale requested by the environment is invalid

Analysis and Clarification:

This error typically arises due to the following reasons:

1. Locale Mismatch: The old and new PostgreSQL versions might have different default locales, or your system's locale settings might not be compatible with the new PostgreSQL version.
2. Missing Locale: The specific locale required by the new PostgreSQL version might be missing from your system.

Solution and Steps:

1. Identify the Required Locale:

   • Start by checking the locale settings of your old and new PostgreSQL installations:

   psql -d postgres -c "SHOW lc_ctype;" 
   

   • The output will show the lc_ctype setting, which indicates the locale used for character classification.
   • Ensure the lc_ctype setting matches between the old and new PostgreSQL versions. If it doesn't, you need to find the required locale.
   • You can use locale -a to list all available locales on your system.

2. Install the Missing Locale:

   • If the required locale is not present, you need to install it using your system's package manager.
   • For example, on Debian-based systems:

   sudo apt-get install language-pack-en
   

   • Replace "en" with the appropriate language code if necessary.

3. Set Environment Variables:

   • Before running pg_upgradecluster, set the following environment variables:

   export LC_ALL=en_US.UTF-8
   export LANG=en_US.UTF-8
   

   • Ensure you replace "en_US.UTF-8" with the locale you identified as required.

4. Run pg_upgradecluster:

   • Retry the pg_upgradecluster command after setting the environment variables:

   sudo pg_upgradecluster 12/main 15/main -d /path/to/datadir
   

Additional Tips:

• Check PostgreSQL Documentation: For more detailed information on locales and their configuration in PostgreSQL, consult the official PostgreSQL documentation.
• Review Upgrade Notes: Read the release notes for the specific PostgreSQL version you're upgrading to. They often contain information about locale-related changes and potential issues.

By following these steps, you should be able to resolve the "Error: the locale requested by the environment is invalid" error and successfully upgrade your PostgreSQL cluster.

References:

• PostgreSQL Documentation: Locale
• PostgreSQL Documentation: pg_upgradecluster