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Fix #118 against 4-0-stable #239

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Fix for #118 against 4-0-stable.

This is really mostly @ofavre's work from awhile ago, I just updated it for 4-0-stable.

ofavre and others added some commits Mar 17, 2013

Make union/except/intersect chainable as SelectManager
Fixes rails/arel#118
Fixes rails/arel#98


@ofavre ofavre referenced this pull request in rails/rails Jan 19, 2014


ActiveRecord UNION left out #939

ofavre commented Jan 19, 2014

Once merged, don't forget to update the code at yakaz/rails@29b8ebd (relation-unions-v3.2.2 branch), in order to resolve rails/rails#939!
EXCEPT and INTERSECT can be exposed too.
Thanks for taking this forward!

@ghost ghost assigned rafaelfranca Jan 19, 2014

bithive commented Mar 18, 2014

Thanks for your work on this @ofavre and @jsanders. I would love to see this get merged, as it is very helpful in one of my projects.

This may be unrelated but in using this new functionality I've noticed parameters don't seem to get bound when using associations in the method chain. I am working around this by writing e.g. Item.where(catalog: self) where I would normally just write items otherwise I get ActiveRecord::StatementInvalid: PG::UndefinedParameter: ERROR: there is no parameter $1

@bithive: Hmm, haven't seen that... How do you have your association set up?

bithive commented Mar 18, 2014

Hopefully this will make sense. It's not a big deal, and perhaps just a gap in my understanding of how to use Arel properly. I know what I am doing is unusual, but there is a reason.

create_table :values do |t|
  t.string :type,  null: false
  t.text   :value, null: true

  t.references :field, null: false
  t.references :item

class Value < ActiveRecord::Base
  belongs_to :field
  belongs_to :item

class Item < ActiveRecord::Base
  belongs_to :catalog
  has_many :values

class Catalog < ActiveRecord::Base
  has_many :items
  has_many :values, through: :items

  # This works for me
  def where attributes
    values_table = Value.arel_table

    queries = attributes.map do |key, value|
      Item.where(catalog: self).joins(:values).where(

    Item.find_by_sql queries.inject(&:intersect).to_sql

  # This doesn't work
  def terse_where attributes
    queries = attributes.map do |key, value|
      values.where(field_id: field_ids_from_tokens[key.to_s], value: value)

    Item.find_by_sql queries.inject(&:intersect).to_sql

In the console first method generates SQL containing "items"."catalog_id" = 1 and succeeds while the latter generates "items"."catalog_id" = $1 and then complains about the undefined parameter.

tamird commented Sep 16, 2014

did this ever actually get fixed on master?

@tamird: No. I'm working on updating this patch for 5.0.1 (so that it can be used with rails 4.1) as we speak.

tamird commented Sep 26, 2014

@jsanders I suggest writing the patch against master first

@tamird: Took your advice :)

Closing this in favor of #320.

@jsanders jsanders closed this Sep 26, 2014

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