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Published Sep. 10, 2025

Illegal mix of collations during upgrade process

Written By

Dávid Hegedüs

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Issue

  • You might encounter the following error or similar during the upgrade process if your database's collation differs from the collation of the tables:
    com.liferay.portal.kernel.upgrade.UpgradeException: java.sql.SQLException: Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8mb4_0900_ai_ci,IMPLICIT) for operation '='
       at com.liferay.portal.kernel.upgrade.UpgradeProcess.upgrade(UpgradeProcess.java:136) ~[portal-kernel.jar:?]
       at com.liferay.portal.upgrade.internal.executor.UpgradeExecutor._executeUpgradeInfos(UpgradeExecutor.java:198) ~[bundleFile:?]
       at com.liferay.portal.upgrade.internal.executor.UpgradeExecutor.executeUpgradeInfos(UpgradeExecutor.java:144) ~[bundleFile:?]
       at com.liferay.portal.upgrade.internal.executor.UpgradeExecutor.execute(UpgradeExecutor.java:116) ~[bundleFile:?]
       at com.liferay.portal.upgrade.internal.registry.UpgradeStepRegistratorTracker$UpgradeStepRegistratorServiceTrackerCustomizer.addingService(UpgradeStepRegistratorTracker.java:184) [bundleFile:?]
       at com.liferay.portal.upgrade.internal.registry.UpgradeStepRegistratorTracker$UpgradeStepRegistratorServiceTrackerCustomizer.addingService(UpgradeStepRegistratorTracker.java:126) [bundleFile:?]
       at org.osgi.util.tracker.ServiceTracker$Tracked.customizerAdding(ServiceTracker.java:943) [org.eclipse.osgi.jar:?]

 

Environment

  • Liferay DXP 7.0+
  • Upgrades

 

Resolution

  • The issue occurs when importing dumps in a new database before Liferay Upgrade. After importing the data, you can check if there is any Collation mismatch (MySQL): 
    USE lportal;

    # Check the database

    SELECT @@character_set_database, @@collation_database;

    # Check all the tables

    SHOW TABLE STATUS;
  • If you find any differences between table and its database, you will need to do one of this options:
  • For explanation purposes, there will be a database A with collation utf8mb4_0900_ai_ci, and a database B with collation utf8mb4_general_ci. The dump is exported from database A and imported in database B.
  • Option 1: Keep the collation of database A
    • It is usually the easiest option. 
    • Before running any upgrade, you will need to update Database B: 
      ALTER DATABASE lportal CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
    • Run the upgrade as normal.
  • Option 2: Keep the collation of database B
    • Before running any upgrade, you will need to alter every table imported in the database B.  
      ALTER TABLE `account_` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
      ALTER TABLE `address` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
      ALTER TABLE ...
      ...
    • Run the upgrade as normal.
  • If you have any doubt in which collation you may choose, create a new support ticket with your enterprise subscription.

 

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