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class RemoveDuplicateTags < ActiveRecord::Migration
def up
select_all("SELECT name, COUNT(id) as cnt FROM tags GROUP BY name HAVING COUNT(id) > 1").each do |tag|
tag_name = quote_string(tag["name"])
duplicate_ids = select_all("SELECT id FROM tags WHERE name = '#{tag_name}'").map{|tag| tag["id"]}
origin_tag_id = duplicate_ids.first
duplicate_ids.delete origin_tag_id
execute("UPDATE taggings SET tag_id = #{origin_tag_id} WHERE tag_id IN(#{duplicate_ids.join(",")})")
execute("DELETE FROM tags WHERE id IN(#{duplicate_ids.join(",")})")
end
end
def down
end
end
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