-- Add unique keyword_i18n locale constraint

-- First we have to delete the duplicates that already exists (keywords 1316-1326; 138 keywords_i18n entries)
with duplicates as (
	select duplicate.id duplicate_id, *
	from keywords_i18n first
	-- inner join the same table where keyword_id, locale_id AND value must all be the same,
	-- i.e. only duplicate translations with the same translated value will be included
	join keywords_i18n duplicate using (keyword_id, locale_id, value)
	where first.id <> duplicate.id
	-- only include the last copy, so we dont delete the original
	and duplicate.id > first.id
) delete from keywords_i18n where id in (select duplicate_id from duplicates);


-- Now we are allowed to add our constraint
ALTER TABLE keywords_i18n ADD UNIQUE (keyword_id, locale_id);