Since I migrated D7 to D8 I suffer from the following problem and need help regarding mining the data that could be useful to make a fine report to the Drupal community.

The story:

When you visit nodes created before migration, you can see their taxonomy terms.

If I save a node with taxonomy data that was created before migration - All its taxonomy data is vanished if its from selection box or radio buttons (if its from autocomplete, the node saves just fine, as weird as it sounds)... It happens in all nodes, and in all content types, (even new ones I create after migration whether from migrated or new content types).

A milestone in my efforts to understand why it happens is this:

When I save any taxonomy vocabulary like in the following image, all of its terms, including the terms of all other vocabularies are just suddenly deleted... Insane as it sounds --- Right after I hit "Save", all of the terms in all vocabularies in the site, just vanish.

But this deletion is only in the UI level; that is, If I go to the table containing taxonomy terms, that is taxonomy_term_field_data I can see all 30 terms that appear in all nodes.

I have consulted a Drupal programmer on this and he told me this is most certainly a migration bug, given it happens on an all-core site and there are no errors in drush ws --full.


I don't ask anyone to debug this for me; Since I learn basic programming and haven't yet learned to debug, all I am asking is what PDO data should I monitor and present in my report to the Drupal community.

I would thank you dearly for giving me any direction because I suffer from this problem very much.

enter image description here

  • You should open a core bug report, this is probably enough information already for a start. You could list the machine names (vid) of your vocabularies and if it somehow changes after saving.
    – Berdir
    Commented Aug 17, 2016 at 18:37
  • I've already opened this but a few days passed and there is no answer there, not even on where and how to get the desired data and what exactly to check: drupal.org/node/2783423
    – user16289
    Commented Aug 17, 2016 at 19:04
  • No solution*, I meant...
    – user16289
    Commented Aug 17, 2016 at 21:00
  • @Benia : wow, this seems a tough issue to debug! 2 more thoughts that may help a ittle ... (1) if using selection box, is the result the same if you allow a single value versus allow multiple values? (2) The taxonomy terms, were they created as part of the migration also. If so is the result the same if you (temporary) create a new taxonomy? Extra thought: as a workarund, would it be an option to replace such taxonomy (term reference) by an entity reference equivalent? Commented Aug 18, 2016 at 5:59
  • 1) The result is always "None" with either selection-boxes or radio-buttons. 2) Same goes for new taxonomy. 3) It can be nice but this problem regards about 350 existing nodes... I must solved it as it is...
    – user16289
    Commented Aug 18, 2016 at 6:02

1 Answer 1


You should look into the database if the taxonomy terms are deleted indeed or just have changed the tid, the language or anything else.

The most probable is the terms are not deleted but when you try to load them by some parameters the parameters has changed and the result is no terms.

  • Indeed, the terms are not deleted from the tables themselves... Anyway, let's assume I click "Save" and everything's deleted from the UI (but not from tables themselves of course). What then? I mean, even it saved in a degenerative way to the SQL, the source is PDO --- Can I say what and where is the PDO problem from comparing 2 variants of the table ? (One before clicking "Save" and one afterwards).
    – user16289
    Commented Aug 23, 2016 at 9:43

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