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doc/solving-database-migration-issues.markdown

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+Solving Database Migration Issues
+=================================
+
+- SQL migrations are executed automatically when you upgrade Kanboard to a new version
+- For Postgres and Mysql, the current schema version number is stored in the table `schema_version` and for Sqlite this is stored in the variable `user_version
+- Migrations are defined in the file `app/Schema/<DatabaseType>.php`
+- Each function is a migration
+- Each migration is executed in a transaction
+- If migration generate an error, a rollback is performed
+
+When upgrading:
+
+- Always backup your data
+- Do not run migrations in parallel from multiple processes
+
+If you got the error "Unable to run SQL migrations [...]", here are the steps to fix it manually:
+
+1. Open the file corresponding to your database `app/Schema/Sqlite.php` or `app/Schema/Mysql.php`
+2. Go to the failed migration function
+3. Execute manually the SQL queries defined in the function
+4. If you encounter an error, report the issue to the bug tracker with the exact SQL error
+5. When all SQL statements of the migration are executed, update the schema version number
+6. Run other migrations