From 5f521cbff3c8a46cfc8e16b234294a20c285d00d Mon Sep 17 00:00:00 2001
From: Sean Griffin <sean@thoughtbot.com>
Date: Fri, 26 Dec 2014 16:28:36 -0700
Subject: [PATCH] Go through normal `where` logic in uniqueness validation

This code could use some much heavier refactoring. It looks like
`build_relation` duplicates most of the logic of `Relation#where` and
`PredicateBuilder` with regards to handling associations and attribute
aliases
---
 .../lib/active_record/validations/uniqueness.rb        | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 255063e951..c4ff2e3ef3 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -16,9 +16,8 @@ module ActiveRecord
         value = map_enum_attribute(finder_class, attribute, value)
 
         relation = build_relation(finder_class, table, attribute, value)
-        relation = relation.and(table[finder_class.primary_key.to_sym].not_eq(record.id)) if record.persisted?
+        relation = relation.where.not(finder_class.primary_key => record.id) if record.persisted?
         relation = scope_relation(record, table, relation)
-        relation = finder_class.unscoped.where(relation)
         relation = relation.merge(options[:conditions]) if options[:conditions]
 
         if relation.exists?
@@ -65,13 +64,16 @@ module ActiveRecord
           value = value.to_s[0, column.limit]
         end
 
+        # FIXME: Remove this when type casting is removed from Arel (Rails 5.1)
         value = Arel::Nodes::Quoted.new(value)
-        if !options[:case_sensitive] && value && column.text?
+
+        comparison = if !options[:case_sensitive] && value && column.text?
           # will use SQL LOWER function before comparison, unless it detects a case insensitive collation
           klass.connection.case_insensitive_comparison(table, attribute, column, value)
         else
           klass.connection.case_sensitive_comparison(table, attribute, column, value)
         end
+        klass.unscoped.where(comparison)
       end
 
       def scope_relation(record, table, relation)
@@ -82,7 +84,7 @@ module ActiveRecord
           else
             scope_value = record._read_attribute(scope_item)
           end
-          relation = relation.and(table[scope_item].eq(scope_value))
+          relation = relation.where(scope_item => scope_value)
         end
 
         relation