Combine two ActiveRecord Relation objects

Question

Suppose I have the following two objects   first name relation   User where  first name   gt   Tobias     ActiveRecord  Relation last name relation    User where  last name    gt   F  nke     ActiveRecord  Relation   is it possible to combine the two relations to produce one ActiveRecord  Relation object containing both conditions   Note  I m aware that I can chain the wheres to get this behavior  what I m really interested in is the case where I have two separate ActiveRecord  Relation objects

User · Answer

Brute force it   first name relation   User where  first name   gt   Tobias     ActiveRecord  Relation last name relation    User where  last name    gt   F  nke     ActiveRecord  Relation  all name relations   User none first name relation each do  ar    all name relations new ar  end last name relation each do  ar    all name relations new ar  end

User · Answer

merge actually doesn t work like OR  It s simply intersection  AND    I struggled with this problem to combine to ActiveRecord  Relation objects into one and I didn t found any working solution for me    Instead of searching for right method creating an union from these two sets  I focused on algebra of sets  You can do it in different way using De Morgan s law  ActiveRecord provides merge method  AND  and also you can use not method or none of  NOT     search where none of search where not id  ids to exclude  merge search where not  title ILIKE         query         You have here  A u B     A    B   UPDATE  The solution above is good for more complex cases   In your case smth like that will be enough   User where  first name LIKE   OR last name LIKE      Tobias    F  nke

User · Answer

There is a gem called active record union that might be what you are looking for    It s example usages is the following   current user posts union Post published  current user posts union Post published  where id   6  7   current user posts union  published at  lt      Time now  user 1 posts union user 2 posts  union Post published  user 1 posts union all user 2 posts

User · Answer

I ve been able to accomplish this  even in many odd situations  by using Rails  built-in Arel   User where    User arel table  first name  eq  Tobias   or      User arel table  last name  eq  F  nke           This merges both ActiveRecord relations by using Arel s or     Merge  as was suggested here  didn t work for me   It dropped the 2nd set of relation objects from the results

User · Answer

If you have an array of activerecord relations and want to merge them all  you can do   array inject  merge

User · Answer

This is how I ve  handled  it if you use pluck to get an identifier for each of the records  join the arrays together and then finally do a query for those joined ids     transaction ids    club type a trans pluck  id     club type b transactions pluck  id     club type c transactions pluck  id     transactions   Transaction where id  transaction ids  limit 100

User · Answer

Relation objects can be converted to arrays  This negates being able to use any ActiveRecord methods on them afterwards  but I didn t need to  I did this   name relation   first name relation   last name relation   Ruby 1 9  rails 3 2

User · Answer

If you want to combine using AND  intersection   use merge   first name relation merge last name relation    If you want to combine using OR  union   use or      first name relation or last name relation          Only in ActiveRecord 5   for 4 2 install the where-or backport

[ruby-on-rails] Combine two ActiveRecord::Relation objects

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