Added note about identifier uniqueness for collection fields

[derhansen]

It is important to note, that it should be avoided to have multiple content blocks, which all have a field of the type collection and which all share the same table and which all have the same identifier.

If different content blocks use the same identifier for collection fields that use the same foreign_table (e.g. tt_content), it occurs, that collection children get mixed up.

[nhovratov]

Hm, I don't get it 100% yet.

So even if you have the same identifier across multiple Content Blocks (for tt_content) and prefixing disabled (which will result in duplicate definition of the field), you will never have mixed up childrens because the record is unique. This can only happen, if you have two fields inside one record, which point to the same foreign table. So could you give a concrete example, where this problem happened for you?

My guess is, you either used Record Types / Pages Types or Collections within Collections. But then you need to define shareAcrossTables so that the tablename of the parent is stored anlongside with the foreign key.

[derhansen]

I used Collections within Collections. I first forgot to add shareAcrossTables, but added it later on and the problem with mixed content persited. Anyway, I tried to create an new example, but can not reproduce the problem any more... I will therefore close this PR now, as it is invalid.

Thanks for your quick answer and thanks a lot for all your work on Content Blocks 👍