I already had the same error you've got; in fact it's a mistake :
Please double check that the delimiter set in the yml file is the same as in your source file (edit it with notepad++ to be sure). Sometimes Excel change delimiter when reopening csv file before resave it without settings file format.
Also, note the column_names key is not mandatory, as the ...
I was able to accomplish this by creating a custom process plugin for the address field.
The following basically means
use the default process plugin get to look for a source column or constant named menu_link_content to determine the value for bundle.
which most likely returns null.
Try setting it with the default_value plugin instead:
You could also create a process plugin to create the Paragraph inline with the record you are migrating. I can't do piecemeal migrations in my case. The project has about 100,000 nodes and no data structure to 'create' Paragraphs out of. Even if I could, I don't want to have to run that dozens of times to get a full set of data.
Here is a real ...
I got the same error when porting Drupal 8 to localhost.
In my case I found a solution visiting mysite/core/install.php location.
There I saw a detailed error: when backing up from /admin/config/development/backup_migrate some tables were missing. So I backed up full database from phpmyadmin, and problem was solved.
Without knowing your content model, you can't answer this question directly, but what you'll need to do is query your node title for every fid entry for your source file entities table. You can do that in many places (e.g. source/process plugin) with your existing source plugin being a good place.
Using your custom file_entity source plugin as an example, ...
Yes. If you're doing a "one-and-done" migration you can remove the tables. Just make sure to:
uninstall the migration modules
remove your relevant migration config
then remove your DB tables once you have no code/config dependant on these tables.
Note, the caveat is you're wiping out your migration history.
The migration framework has an ongoing issue ...