drop rails lower than 6.0

.github/workflows/testing.yml

@@ -39,8 +39,6 @@ jobs:
       matrix:
         # just define specific versions for each rails version
         include:
-          - ruby: 2.6
-            rails: 5.2
           - ruby: 2.6
             rails: "6.0"
           - ruby: "3.0"

README.md

@@ -17,7 +17,7 @@ user_1.posts.union(user_2.posts).union(Post.published)
 user_1.posts.union_all(user_2.posts)
 ```
 
-ActiveRecordUnion is tested against Rails 5.0, 5.1, and 5.2. It should also work on Rails 4.2. It may or may not work on Rails 4.0/4.1.
+ActiveRecordUnion is tested against Rails 6.0, 6.1, 7.0, 7.1, 7.2 and 8.0.
 
 If you are using Postgres, you might alternatively check out [ActiveRecordExtended](https://github.com/georgekaraszi/ActiveRecordExtended) which includes support for unions as well as other goodies.
 
@@ -218,7 +218,7 @@ This public domain dedication follows the the CC0 1.0 at https://creativecommons
   1. Install MySQL and PostgreSQL.
   2. You need to be able to connect to a local MySQL and Postgres database as the default user, so the specs can create a `test_active_record_union` database. To set up the users this test expects, execute `bin/create-db-users` (or set the environment variables referenced in `spec/support/databases.rb`).
   3. Run `rake` to test with all supported Rails versions. All needed dependencies will be installed via Bundler (`gem install bundler` if you happen not to have Bundler yet).
-  4. Run `rake test_rails_4_2` or `rake test_rails_5_2` etc. to test a specific Rails version.
+  4. Run `rake test_rails_8_0` or `rake test_rails_7_2` etc. to test a specific Rails version.
 4. There is also a `bin/console` command to load up a REPL for playing around
 5. Commit your changes (`git commit -am 'Add some feature'`)
 6. Push to the branch (`git push origin my-new-feature`)

active_record_union.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/}) + spec.files.grep(%r{^bin/})
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "activerecord", ">= 5.2"
+  spec.add_dependency "activerecord", ">= 6.0"
 
   spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"

lib/active_record_union/active_record/relation/union.rb

@@ -41,41 +41,8 @@ def set_operation(operation, relation_or_where_arg, *args)
         build_union_relation(from, other)
       end
 
-      if ActiveRecord.gem_version >= Gem::Version.new('5.2.0.beta2')
-        # Since Rails 5.2, binds are maintained only in the Arel AST.
-        def build_union_relation(arel_table_alias, _other)
-          self.klass.unscoped.from(arel_table_alias)
-        end
-      elsif ActiveRecord::VERSION::MAJOR >= 5
-        # In Rails >= 5.0, < 5.2, binds are maintained only in ActiveRecord
-        # relations and clauses.
-        def build_union_relation(arel_table_alias, other)
-          relation = self.klass.unscoped.spawn
-          relation.from_clause =
-            UnionFromClause.new(arel_table_alias, nil,
-                                self.bound_attributes + other.bound_attributes)
-          relation
-        end
-
-        class UnionFromClause < ActiveRecord::Relation::FromClause
-          def initialize(value, name, bound_attributes)
-            super(value, name)
-            @bound_attributes = bound_attributes
-          end
-
-          def binds
-            @bound_attributes
-          end
-        end
-      else
-        # In Rails 4.x, binds are maintained in both ActiveRecord relations and
-        # clauses and also in their Arel ASTs.
-        def build_union_relation(arel_table_alias, other)
-          relation = self.klass.unscoped.from(arel_table_alias)
-          relation.bind_values = self.arel.bind_values + self.bind_values +
-                                 other.arel.bind_values + other.bind_values
-          relation
-        end
+      def build_union_relation(arel_table_alias, _other)
+        self.klass.unscoped.from(arel_table_alias)
       end
 
       def verify_relations_for_set_operation!(operation, *relations)