I’m in the middle of a Drupal 8 -> Drupal 9 migration. After the data migration I decided to nose around the database and found a number of tables that I believe are vestigial and should’ve been dropped a while ago:
- Migration Tables - (migrate_map_upgrade_d7_*). tables that were used when I migrated this Drupal 7 into D8 5 years ago.
- Empty Field Tables (node__field_*) and Node Field Revision Tables (node_revision__field_*) that were from fields that were deleted years ago, generally from deleted content types. This also shows up for paragraph, taxonomy and media bundles.
The fact that this stuff lingers around surprised me. In my database management days, cruft always bothered me. Is there any danger in clearing this out by hand (dropping tables)? Do any developers monitor these things?