Problems with postgres datebase migration (11 to 15) during SonarQube upgrade (8.9.9 to 9.9.4)

In our project we want to update SonarQube (Developer Edition) from version 8.9.9 to version 9.9.4. For this it is necessary to update the Postgres 11 database (runs in a Docker container) to Postgres 15. We used this guide. Unfortunately, with the result that the projects are not visible afterwards. However, they can be opened via the URL with project key. However, there are no findings in the projects. Likewise, the quality gates lack the assignment to the rules. Therefore, we presume that during the migration of the database something went wrong. We would be grateful for information about a possible cause of error.

Sounds like a bad Elasticsearch index. Follow the instructions here.

Thanks for your proposal. During our migration we removed the data folder. But we didn´t try the exact approach you posted. But we found another (more generic) way to migrate the database by use of the SonarQube database copy tool. With this approach we did not face the problem.