Scope for leaves #246

antstorm · 2015-12-05T19:33:22Z

Hi,

Here's a pure-SQL support for getting all the leaves of the tree. Basically making sure that for every record there's other record that references it's ancestry. I had to use OR in the JOIN because ancestry might be nil.

kbrock · 2015-12-06T06:05:37Z

I'd too would like to add postgres specific version of some other methods. e.g.: sorting by nulls vs using a case statement.

At a hight level, is the code here the best way to introduce database specific sql?

antstorm · 2015-12-06T13:15:54Z

@kbrock I'd say if more methods start to appear then it's better to extract them into an SQLHelper module or something. Would be great for adapters to support that, but I think it might be out of their scope.

kbrock · 2016-01-01T01:46:03Z

Hi @antstorm It is a long shot, but seeing if we can put this abstraction into arel here

antstorm · 2016-01-01T19:22:01Z

@kbrock good shout, let's see what the arel guys think. Judging by the previous PR attempt they're not very positive about supporting infix operators.

antstorm · 2016-03-08T09:24:02Z

@kbrock nice one, I never thought it would make it's way into arel! Although I don't think I can use that here, since ancestry depends on activerecord >= 3.0.0.

ImDineshSaini · 2016-03-08T09:34:45Z

Alternate is add a file in config/initializer

module Ancestry
  module ClassMethods
    # Scope that returns all the leaves
    def leaves
      id_column = "#{table_name}.id"
      id_column_as_text = sql_cast_as_text(id_column)
      parent_ancestry = sql_concat("#{table_name}.#{ancestry_column}", "'/'", id_column_as_text)

      joins("LEFT JOIN #{table_name} AS c ON c.#{ancestry_column} = #{id_column_as_text} OR c.#{ancestry_column} = #{parent_ancestry}").
        group(id_column).
        having('COUNT(c.id) = 0')
    end

    private

    def sql_concat *parts
      if ActiveRecord::Base.connection.adapter_name.downcase == 'sqlite'
        parts.join(' || ')
      else
        "CONCAT(#{parts.join(', ')})"
      end
    end

    def sql_cast_as_text column
      text_type = if ActiveRecord::Base.connection.adapter_name.downcase == 'mysql2'
        'CHAR'
      else
        'TEXT'
      end

      "CAST(#{column} AS #{text_type})  collate utf8_unicode_ci"
    end
  end
end

kbrock · 2016-10-07T01:20:14Z

@antstorm Arel supports concat (see reference above to rails PR)
I'd like to release ancestry v3 with rails 4.x support and above.
And then start to use stuff like this.

Ancestry 2.1.x can support older rails, just not get these newer features.
Are you still using ancestry? What version of rails do you need to support?

antstorm · 2016-10-07T13:14:26Z

@kbrock I'm not using ancestry in my current projects, but I'm happy to shape this PR into something mergeable, dropping rails < 4 support.

fursich · 2018-07-10T12:35:39Z

Hi @antstorm , would you be comfortable if I rebase this PR and give it a new life, since I found it much better than mine (#388) in terms of SQL efficiency and simplicity.
As a daily user of ancestry I appreciate the efforts made here, and leaving this feature un-merged is just a shame..

(@kbrock I'm assuming currently nobody is working on it, let me know if I'm in a totally wrong place.. you might already have clear ideas about what to be done.)

Hope that makes sense 😸

antstorm · 2018-07-10T20:48:03Z

@fursich sure, I've rebased it. Do you think there's anything missing from it?

coveralls · 2018-07-10T21:03:08Z