Ordering categories using SQL

(Keith John Hutchison) #1

The following code changes the order of categories to be alphanumeric using SQL.

Preconditions.
Postgres backend

UPDATE categories
SET POSITION = subquery.position
FROM (
	SELECT POSITION
	, CASE WHEN category_id = 0 THEN parent_category_id ELSE category_id END category_id 
	, CASE WHEN category_id = 0 THEN parent_category_name ELSE category_name END category_name 
	FROM (
		SELECT ROW_NUMBER - 1 AS POSITION
		, parent_category_id
		, parent_category_name
		, category_id
		, category_name
		FROM ( SELECT row_number() OVER ( ORDER BY parent_category_name, category_name )
		, * FROM (
		SELECT * FROM (
			SELECT id parent_category_id
			, name parent_category_name 
			, 0 category_id
			, cast('' AS text) category_name
			FROM categories 
			WHERE parent_category_id IS NULL ORDER BY name
		) parent_categories
		UNION 
		(
			SELECT child.parent_category_id
			, parent.name parent_category_name 
			, child.id category_id
			, child.name category_name
			FROM categories child
			INNER JOIN categories parent
			ON child.parent_category_id = parent.id
			WHERE child.parent_category_id IS NOT NULL ORDER BY child.name
		) 
		) parents_with_children
		ORDER BY parent_category_name, category_name
		) ordered_parents_with_children
		ORDER BY ROW_NUMBER
	) category_positions_sorted_alphabetically
) subquery
WHERE id = subquery.category_id ;

I ran the code by starting up a psql session.

/var/discourse/launcher enter app
su postgres
psql discourse

and then executing the SQL.

Running from rails console.

ActiveRecord::Base.connection.execute("UPDATE categories SET POSITION = subquery.position FROM ( SELECT POSITION , CASE WHEN category_id = 0 THEN parent_category_id ELSE category_id END category_id , CASE WHEN category_id = 0 THEN parent_category_name ELSE category_name END category_name FROM ( SELECT ROW_NUMBER - 1 AS POSITION , parent_category_id , parent_category_name , category_id , category_name FROM ( SELECT row_number() OVER ( ORDER BY parent_category_name, category_name ) , * FROM ( SELECT * FROM ( SELECT id parent_category_id , name parent_category_name , 0 category_id , cast('' AS text) category_name FROM categories WHERE parent_category_id IS NULL ORDER BY name ) parent_categories UNION ( SELECT child.parent_category_id , parent.name parent_category_name , child.id category_id , child.name category_name FROM categories child INNER JOIN categories parent ON child.parent_category_id = parent.id WHERE child.parent_category_id IS NOT NULL ORDER BY child.name ) ) parents_with_children ORDER BY parent_category_name, category_name ) ordered_parents_with_children ORDER BY ROW_NUMBER ) category_positions_sorted_alphabetically ) subquery WHERE id = subquery.category_id")
1 Like
Sorting Categories by Name
(Jay Pfaffman) #2

I’ve not tested this recently but here’s at least a hint for how to alpha-sort categories at the rails console:

# alpha sort all categories matching search and their sub-categories

  def sort_matching_categories_and_subcategories(search)
    categories = Category.where("name like ?", search)
    position = 100
    categories.order(:name).each do |cat|
      position += 5
      cat.position = position
      cat.save!()
      c_position = 0
      children = Category.where(:parent_category_id=>cat.id)
      children.order(:name).each do |c|
        c_position += 5
        c.position = c_position
        c.save!()
      end
    end
  end


 # alpha sort subcategories of a single category matching search
def sort_matching_subcategories(search)
  categories = Category.where("name like ?", search)
  if categories.count > 1
    puts "Found more than one category"
  end
  categories.order(:name).each do |cat|
    c_position = 5
    children = Category.where(:parent_category_id=>cat.id)
    children.order(:name).each do |c|
      c_position += 5
      c.position = c_position
      c.save!()
    end
  end
end
1 Like
(Keith John Hutchison) #3

Thanks @pfaffman

Based on your ruby code I came up with

def sort_categories_by_name(skip=0)
  
  parents = Category.where("parent_category_id is null")
  position = 0
  parents.order(:name).each do |parent|
    parent.position = position
    parent.save!()
    position += (1+skip)
    children = Category.where(:parent_category_id=>parent.id)
    children.order(:name).each do |child|
      child.position = position
      child.save!()
      position += (1+skip)  
    end
  end
  
  position += -(1+skip)  
  return position
  
end

sort_categories_by_name
1 Like