Field of type text: all options, that are not unique are loaded when editing the field

[dasistwas]

How to reproduce

1. Create a text field ( do not check unique option )
2. Add several entries using the text field
3. Edit the text field settings again -> Result all entry ids using the text field are shown and slows down loading the page when there are a lot of entries.

Solution: Do not load the entry ids, just make a simpler check of there are the field is not unique. Maybe similar to that query:

SELECT username, email, COUNT(*)
FROM users
GROUP BY username, email
HAVING COUNT(*) > 1
LIMIT 2

[michaelpollak]

I should write a paper so this came with perfect timing... ;)
Removed most of the duplicate code for more performance. We now only check if we see a duplicate entry (has_duplicate) and prevent activation of unique.

It may be smart to keep the "print_list_of_duplicates" functionality for a popup?
Alternatively we could add a switch, under 10 duplicates show where they are, over just ignore the list and tell the user that he/she can't enable unique?