Come together with the global Drupal community in Rotterdam, 28 Sept – 1 Oct 2026. Sessions, contribution, connection, and Early Bird savings until 8 June.Ambiguous key fields in queries
If a column name in the source key passed to the map key appears in more than one table of the source query, you will get an error along the
Benchmarking performance of the migration
Migrate allows you to benchmark the migration and get execution time.
Cardinality violation with UNION queries
When your source query is a union, like
Chickens and eggs: using stubs
Suppose you are migrating articles from an external site into Drupal article nodes. These articles may reference each other, so in Drupal
Clean up migrate config during uninstall of migration
You might be getting several messages like this when you try to uninstall and reinstall a migration module:
Cross-database migrations
If your source data is in a database supported by the Drupal database API, such as MySQL or Postgres, and your web server has access to that
Highwater marks
By default, each time a migration is run, any previously unimported source items are imported (along with any previously-imported items
Multiple destination objects or entities
The Migration class is built on the fundamental assumption that there is a one-to-one correspondence between source rows coming in and
Multiple source data rows
The Migration class is built on the fundamental assumption that there is a one-to-one correspondence between source rows coming in and
Non-migration "migrations" - using MigrationBase
Describe how arbitrary processes can be performed in the course of migration using the MigrationBase class...
Preserving user passwords
One challenge frequently dealt with in migrations is handling user passwords. Usually the passwords on the old system are encrypted, and
Preventing deletion of files on rollback
If you are populating file fields on migration, and don't want the files to be deleted on rollback (e.g., you copied the files manually into
Running imports and rollbacks from the UI via drush
As explained at Why you should run migrations in Drush rather than the UI, drush is a faster and more robust means of running large
Running out of memory migrating images
Although Migrate detects when PHP is running low of memory and spawns a fresh process in that instance to avoid out-of-memory errors, I have
Source databases with fields/columns named using spaces or reserved words
Drupal's database abstraction layer cannot directly access columns named using spaces or reserved words: [#1426084].
Tuning your Drupal database for data migration
Data migration has different performance characteristics from normal website operations. The construction and delivery of a single web page
Updating existing content rather than importing new content - system-of-record
While the Migrate module was originally developed for the purpose of performing complete site migrations, where the source data is always
