Refactor Active Record to let Arel manage bind params

A common source of bugs and code bloat within Active Record has been the
need for us to maintain the list of bind values separately from the AST
they're associated with. This makes any sort of AST manipulation
incredibly difficult, as any time we want to potentially insert or
remove an AST node, we need to traverse the entire tree to find where
the associated bind parameters are.

With this change, the bind parameters now live on the AST directly.
Active Record does not need to know or care about them until the final
AST traversal for SQL construction. Rather than returning just the SQL,
the Arel collector will now return both the SQL and the bind parameters.
At this point the connection adapter will have all the values that it
had before.

A bit of this code is janky and something I'd like to refactor later. In
particular, I don't like how we're handling associations in the
predicate builder, the special casing of `StatementCache::Substitute` in
`QueryAttribute`, or generally how we're handling bind value replacement
in the statement cache when prepared statements are disabled.

This also mostly reverts #26378, as it moved all the code into a
location that I wanted to delete.

/cc @metaskills @yahonda, this change will affect the adapters

Fixes #29766.
Fixes #29804.
Fixes #26541.
Close #28539.
Close #24769.
Close #26468.
Close #26202.

There are probably other issues/PRs that can be closed because of this
commit, but that's all I could find on the first few pages.

26 files changed, 225 insertions, 329 deletions

diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 938d2645ca..89ce00f98e 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -154,7 +154,7 @@ module ActiveRecord
               stmt.from scope.klass.arel_table
               stmt.wheres = arel.constraints
 
-              count = scope.klass.connection.delete(stmt, "SQL", scope.bound_attributes)
+              count = scope.klass.connection.delete(stmt, "SQL")
             end
           when :nullify
             count = scope.update_all(source_reflection.foreign_key => nil)
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index 42014653e8..30dbdb7fa5 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -23,11 +23,10 @@ module ActiveRecord
           super && reflection == other.reflection
         end
 
-        JoinInformation = Struct.new :joins, :binds
+        JoinInformation = Struct.new :joins
 
         def join_constraints(foreign_table, foreign_klass, join_type, tables, chain)
           joins         = []
-          binds         = []
           tables        = tables.reverse
 
           # The chain starts with the target table, but we want to end with it here (makes
@@ -43,7 +42,6 @@ module ActiveRecord
             join_scope = reflection.join_scope(table, foreign_klass)
 
             if join_scope.arel.constraints.any?
-              binds.concat join_scope.bound_attributes
               joins.concat join_scope.arel.join_sources
               right = joins.last.right
               right.expr = right.expr.and(join_scope.arel.constraints)
@@ -53,7 +51,7 @@ module ActiveRecord
             foreign_table, foreign_klass = table, klass
           end
 
-          JoinInformation.new joins, binds
+          JoinInformation.new joins
         end
 
         def table
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 62948225af..0b29ef2502 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -29,7 +29,7 @@ module ActiveRecord
           arel = query.arel
         end
 
-        result = connection.select_one(arel, nil, query.bound_attributes)
+        result = connection.select_one(arel, nil)
 
         if result.blank?
           size = 0
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index f2715cdab0..f687d3a7e8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -9,30 +9,36 @@ module ActiveRecord
       end
 
       # Converts an arel AST to SQL
-      def to_sql(arel, binds = [])
-        if arel.respond_to?(:ast)
-          collected = visitor.accept(arel.ast, collector)
-          collected.compile(binds, self).freeze
+      def to_sql(arel_or_sql_string, binds = [])
+        if arel_or_sql_string.respond_to?(:ast)
+          unless binds.empty?
+            raise "Passing bind parameters with an arel AST is forbidden. " \
+              "The values must be stored on the AST directly"
+          end
+          sql, binds = visitor.accept(arel_or_sql_string.ast, collector).value
+          [sql.freeze, binds || []]
         else
-          arel.dup.freeze
+          [arel_or_sql_string.dup.freeze, binds]
         end
       end
 
       # This is used in the StatementCache object. It returns an object that
       # can be used to query the database repeatedly.
       def cacheable_query(klass, arel) # :nodoc:
-        collected = visitor.accept(arel.ast, collector)
         if prepared_statements
-          klass.query(collected.value)
+          sql, binds = visitor.accept(arel.ast, collector).value
+          query = klass.query(sql)
         else
-          klass.partial_query(collected.value)
+          query = klass.partial_query(arel.ast)
+          binds = []
         end
+        [query, binds]
       end
 
       # Returns an ActiveRecord::Result instance.
       def select_all(arel, name = nil, binds = [], preparable: nil)
-        arel, binds = binds_from_relation arel, binds
-        sql = to_sql(arel, binds)
+        arel = arel_from_relation(arel)
+        sql, binds = to_sql(arel, binds)
         if !prepared_statements || (arel.is_a?(String) && preparable.nil?)
           preparable = false
         else
@@ -131,20 +137,23 @@ module ActiveRecord
       #
       # If the next id was calculated in advance (as in Oracle), it should be
       # passed in as +id_value+.
-      def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])
-        value = exec_insert(to_sql(arel, binds), name, binds, pk, sequence_name)
+      def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil)
+        sql, binds = to_sql(arel)
+        value = exec_insert(sql, name, binds, pk, sequence_name)
         id_value || last_inserted_id(value)
       end
       alias create insert
 
       # Executes the update statement and returns the number of rows affected.
-      def update(arel, name = nil, binds = [])
-        exec_update(to_sql(arel, binds), name, binds)
+      def update(arel, name = nil)
+        sql, binds = to_sql(arel)
+        exec_update(sql, name, binds)
       end
 
       # Executes the delete statement and returns the number of rows affected.
-      def delete(arel, name = nil, binds = [])
-        exec_delete(to_sql(arel, binds), name, binds)
+      def delete(arel, name = nil)
+        sql, binds = to_sql(arel)
+        exec_delete(sql, name, binds)
       end
 
       # Returns +true+ when the connection adapter supports prepared statement
@@ -430,11 +439,12 @@ module ActiveRecord
           row && row.first
         end
 
-        def binds_from_relation(relation, binds)
-          if relation.is_a?(Relation) && binds.empty?
-            relation, binds = relation.arel, relation.bound_attributes
+        def arel_from_relation(relation)
+          if relation.is_a?(Relation)
+            relation.arel
+          else
+            relation
           end
-          [relation, binds]
         end
 
         # Fixture value is quoted by Arel, however scalar values
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
index 077e8beba9..ecf5201d12 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
@@ -92,8 +92,8 @@ module ActiveRecord
 
       def select_all(arel, name = nil, binds = [], preparable: nil)
         if @query_cache_enabled && !locked?(arel)
-          arel, binds = binds_from_relation arel, binds
-          sql = to_sql(arel, binds)
+          arel = arel_from_relation(arel)
+          sql, binds = to_sql(arel, binds)
           cache_sql(sql, name, binds) { super(sql, name, binds, preparable: preparable) }
         else
           super
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index b637518fc8..7b83bc319c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -24,6 +24,10 @@ module ActiveRecord
           return value.quoted_id
         end
 
+        if value.respond_to?(:value_for_database)
+          value = value.value_for_database
+        end
+
         _quote(value)
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 04e32d03e1..e699a77230 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -7,7 +7,9 @@ require_relative "sql_type_metadata"
 require_relative "abstract/schema_dumper"
 require_relative "abstract/schema_creation"
 require "arel/collectors/bind"
+require "arel/collectors/composite"
 require "arel/collectors/sql_string"
+require "arel/collectors/substitute_binds"
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
@@ -129,19 +131,6 @@ module ActiveRecord
         end
       end
 
-      class BindCollector < Arel::Collectors::Bind
-        def compile(bvs, conn)
-          casted_binds = bvs.map(&:value_for_database)
-          super(casted_binds.map { |value| conn.quote(value) })
-        end
-      end
-
-      class SQLString < Arel::Collectors::SQLString
-        def compile(bvs, conn)
-          super(bvs)
-        end
-      end
-
       def valid_type?(type) # :nodoc:
         !native_database_types[type].nil?
       end
@@ -432,14 +421,14 @@ module ActiveRecord
       end
 
       def case_sensitive_comparison(table, attribute, column, value) # :nodoc:
-        table[attribute].eq(value)
+        table[attribute].eq(Arel::Nodes::BindParam.new(value))
       end
 
       def case_insensitive_comparison(table, attribute, column, value) # :nodoc:
         if can_perform_case_insensitive_comparison_for?(column)
-          table[attribute].lower.eq(table.lower(value))
+          table[attribute].lower.eq(table.lower(Arel::Nodes::BindParam.new(value)))
         else
-          table[attribute].eq(value)
+          table[attribute].eq(Arel::Nodes::BindParam.new(value))
         end
       end
 
@@ -457,24 +446,6 @@ module ActiveRecord
         visitor.accept(node, collector).value
       end
 
-      def combine_bind_parameters(
-        from_clause: [],
-        join_clause: [],
-        where_clause: [],
-        having_clause: [],
-        limit: nil,
-        offset: nil
-      ) # :nodoc:
-        result = from_clause + join_clause + where_clause + having_clause
-        if limit
-          result << limit
-        end
-        if offset
-          result << offset
-        end
-        result
-      end
-
       def default_index_type?(index) # :nodoc:
         index.using.nil?
       end
@@ -609,9 +580,15 @@ module ActiveRecord
 
         def collector
           if prepared_statements
-            SQLString.new
+            Arel::Collectors::Composite.new(
+              Arel::Collectors::SQLString.new,
+              Arel::Collectors::Bind.new,
+            )
           else
-            BindCollector.new
+            Arel::Collectors::SubstituteBinds.new(
+              self,
+              Arel::Collectors::SQLString.new,
+            )
           end
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 5915f0db2d..8a9c497918 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -177,7 +177,8 @@ module ActiveRecord
       #++
 
       def explain(arel, binds = [])
-        sql     = "EXPLAIN #{to_sql(arel, binds)}"
+        sql, binds = to_sql(arel, binds)
+        sql     = "EXPLAIN #{sql}"
         start   = Time.now
         result  = exec_query(sql, "EXPLAIN", binds)
         elapsed = Time.now - start
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
index 00b56ee9ae..a058a72872 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -5,7 +5,7 @@ module ActiveRecord
     module MySQL
       module DatabaseStatements
         # Returns an ActiveRecord::Result instance.
-        def select_all(arel, name = nil, binds = [], preparable: nil) # :nodoc:
+        def select_all(*) # :nodoc:
           result = if ExplainRegistry.collect? && prepared_statements
             unprepared_statement { super }
           else
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
index 8db2a645af..0dd4aac463 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -5,7 +5,8 @@ module ActiveRecord
     module PostgreSQL
       module DatabaseStatements
         def explain(arel, binds = [])
-          sql = "EXPLAIN #{to_sql(arel, binds)}"
+          sql, binds = to_sql(arel, binds)
+          sql = "EXPLAIN #{sql}"
           PostgreSQL::ExplainPrettyPrinter.new.pp(exec_query(sql, "EXPLAIN", binds))
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 10e80179ac..8c12cb09bd 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -203,7 +203,8 @@ module ActiveRecord
       #++
 
       def explain(arel, binds = [])
-        sql = "EXPLAIN QUERY PLAN #{to_sql(arel, binds)}"
+        sql, binds = to_sql(arel, binds)
+        sql = "EXPLAIN QUERY PLAN #{sql}"
         SQLite3::ExplainPrettyPrinter.new.pp(exec_query(sql, "EXPLAIN", []))
       end
 
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 90e4fe98d5..92ecdcae92 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -53,7 +53,7 @@ module ActiveRecord
       im = arel.create_insert
       im.into @table
 
-      substitutes, binds = substitute_values values
+      substitutes = substitute_values values
 
       if values.empty? # empty insert
         im.values = Arel.sql(connection.empty_insert_statement_value)
@@ -67,11 +67,11 @@ module ActiveRecord
         primary_key || false,
         primary_key_value,
         nil,
-        binds)
+      )
     end
 
     def _update_record(values, id, id_was) # :nodoc:
-      substitutes, binds = substitute_values values
+      substitutes = substitute_values values
 
       scope = @klass.unscoped
 
@@ -80,7 +80,6 @@ module ActiveRecord
       end
 
       relation = scope.where(@klass.primary_key => (id_was || id))
-      bvs = binds + relation.bound_attributes
       um = relation
         .arel
         .compile_update(substitutes, @klass.primary_key)
@@ -88,20 +87,14 @@ module ActiveRecord
       @klass.connection.update(
         um,
         "SQL",
-        bvs,
       )
     end
 
     def substitute_values(values) # :nodoc:
-      binds = []
-      substitutes = []
-
-      values.each do |arel_attr, value|
-        binds.push QueryAttribute.new(arel_attr.name, value, klass.type_for_attribute(arel_attr.name))
-        substitutes.push [arel_attr, Arel::Nodes::BindParam.new]
+      values.map do |arel_attr, value|
+        bind = QueryAttribute.new(arel_attr.name, value, klass.type_for_attribute(arel_attr.name))
+        [arel_attr, Arel::Nodes::BindParam.new(bind)]
       end
-
-      [substitutes, binds]
     end
 
     def arel_attribute(name) # :nodoc:
@@ -380,7 +373,7 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      @klass.connection.update stmt, "SQL", bound_attributes
+      @klass.connection.update stmt, "SQL"
     end
 
     # Updates an object (or multiple objects) and saves it to the database, if validations pass.
@@ -510,7 +503,7 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      affected = @klass.connection.delete(stmt, "SQL", bound_attributes)
+      affected = @klass.connection.delete(stmt, "SQL")
 
       reset
       affected
@@ -578,7 +571,8 @@ module ActiveRecord
 
                     conn = klass.connection
                     conn.unprepared_statement {
-                      conn.to_sql(relation.arel, relation.bound_attributes)
+                      sql, _ = conn.to_sql(relation.arel)
+                      sql
                     }
                   end
     end
@@ -663,7 +657,7 @@ module ActiveRecord
 
       def exec_queries(&block)
         skip_query_cache_if_necessary do
-          @records = eager_loading? ? find_with_associations.freeze : @klass.find_by_sql(arel, bound_attributes, &block).freeze
+          @records = eager_loading? ? find_with_associations.freeze : @klass.find_by_sql(arel, &block).freeze
 
           preload = preload_values
           preload += includes_values unless eager_loading?
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index c105abe774..66a9a3c9c9 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -186,7 +186,7 @@ module ActiveRecord
         relation.select_values = column_names.map { |cn|
           @klass.has_attribute?(cn) || @klass.attribute_alias?(cn) ? arel_attribute(cn) : cn
         }
-        result = skip_query_cache_if_necessary { klass.connection.select_all(relation.arel, nil, bound_attributes) }
+        result = skip_query_cache_if_necessary { klass.connection.select_all(relation.arel, nil) }
         result.cast_values(klass.attribute_types)
       end
     end
@@ -262,7 +262,7 @@ module ActiveRecord
           query_builder = relation.arel
         end
 
-        result = skip_query_cache_if_necessary { @klass.connection.select_all(query_builder, nil, bound_attributes) }
+        result = skip_query_cache_if_necessary { @klass.connection.select_all(query_builder, nil) }
         row    = result.first
         value  = row && row.values.first
         type   = result.column_types.fetch(column_alias) do
@@ -313,7 +313,7 @@ module ActiveRecord
         relation.group_values  = group_fields
         relation.select_values = select_values
 
-        calculated_data = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, nil, relation.bound_attributes) }
+        calculated_data = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, nil) }
 
         if association
           key_ids     = calculated_data.collect { |row| row[group_aliases.first] }
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 36d35b98fd..626c50470e 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -317,7 +317,7 @@ module ActiveRecord
 
       relation = construct_relation_for_exists(relation, conditions)
 
-      skip_query_cache_if_necessary { connection.select_value(relation.arel, "#{name} Exists", relation.bound_attributes) } ? true : false
+      skip_query_cache_if_necessary { connection.select_value(relation.arel, "#{name} Exists") } ? true : false
     rescue ::RangeError
       false
     end
@@ -378,7 +378,7 @@ module ActiveRecord
           if ActiveRecord::NullRelation === relation
             []
           else
-            rows = skip_query_cache_if_necessary { connection.select_all(relation.arel, "SQL", relation.bound_attributes) }
+            rows = skip_query_cache_if_necessary { connection.select_all(relation.arel, "SQL") }
             join_dependency.instantiate(rows, aliases)
           end
         end
@@ -426,7 +426,7 @@ module ActiveRecord
 
         relation = relation.except(:select).select(values).distinct!
 
-        id_rows = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, "SQL", relation.bound_attributes) }
+        id_rows = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, "SQL") }
         id_rows.map { |row| row[primary_key] }
       end
 
diff --git a/activerecord/lib/active_record/relation/from_clause.rb b/activerecord/lib/active_record/relation/from_clause.rb
index 03f1202470..c53a682aee 100644
--- a/activerecord/lib/active_record/relation/from_clause.rb
+++ b/activerecord/lib/active_record/relation/from_clause.rb
@@ -10,14 +10,6 @@ module ActiveRecord
         @name = name
       end
 
-      def binds
-        if value.is_a?(Relation)
-          value.bound_attributes
-        else
-          []
-        end
-      end
-
       def merge(other)
         self
       end
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 3b8f8da634..ee7fef4711 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -8,10 +8,9 @@ module ActiveRecord
       @table = table
       @handlers = []
 
-      register_handler(BasicObject, BasicObjectHandler.new)
+      register_handler(BasicObject, BasicObjectHandler.new(self))
       register_handler(Base, BaseHandler.new(self))
-      register_handler(Range, RangeHandler.new)
-      register_handler(RangeHandler::RangeWithBinds, RangeHandler.new)
+      register_handler(Range, RangeHandler.new(self))
       register_handler(Relation, RelationHandler.new)
       register_handler(Array, ArrayHandler.new(self))
     end
@@ -21,11 +20,6 @@ module ActiveRecord
       expand_from_hash(attributes)
     end
 
-    def create_binds(attributes)
-      attributes = convert_dot_notation_to_hash(attributes)
-      create_binds_for_hash(attributes)
-    end
-
     def self.references(attributes)
       attributes.map do |key, value|
         if value.is_a?(Hash)
@@ -56,8 +50,11 @@ module ActiveRecord
       handler_for(value).call(attribute, value)
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
+    def build_bind_attribute(column_name, value)
+      attr = Relation::QueryAttribute.new(column_name.to_s, value, table.type(column_name))
+      Arel::Nodes::BindParam.new(attr)
+    end
+
     protected
 
       attr_reader :table
@@ -68,29 +65,13 @@ module ActiveRecord
         attributes.flat_map do |key, value|
           if value.is_a?(Hash) && !table.has_column?(key)
             associated_predicate_builder(key).expand_from_hash(value)
-          else
-            build(table.arel_attribute(key), value)
-          end
-        end
-      end
-
-      def create_binds_for_hash(attributes)
-        result = attributes.dup
-        binds = []
-
-        attributes.each do |column_name, value|
-          case
-          when value.is_a?(Hash) && !table.has_column?(column_name)
-            attrs, bvs = associated_predicate_builder(column_name).create_binds_for_hash(value)
-            result[column_name] = attrs
-            binds += bvs
-          when table.associated_with?(column_name)
+          elsif table.associated_with?(key)
             # Find the foreign key when using queries such as:
             # Post.where(author: author)
             #
             # For polymorphic relationships, find the foreign key and type:
             # PriceEstimate.where(estimate_of: treasure)
-            associated_table = table.associated_table(column_name)
+            associated_table = table.associated_table(key)
             if associated_table.polymorphic_association?
               case value.is_a?(Array) ? value.first : value
               when Base, Relation
@@ -100,40 +81,14 @@ module ActiveRecord
             end
 
             klass ||= AssociationQueryValue
-            result[column_name] = klass.new(associated_table, value).queries.map do |query|
-              attrs, bvs = create_binds_for_hash(query)
-              binds.concat(bvs)
-              attrs
-            end
-          when value.is_a?(Range) && !table.type(column_name).respond_to?(:subtype)
-            first = value.begin
-            last = value.end
-            unless first.respond_to?(:infinite?) && first.infinite?
-              binds << build_bind_attribute(column_name, first)
-              first = Arel::Nodes::BindParam.new
+            queries = klass.new(associated_table, value).queries.map do |query|
+              expand_from_hash(query).reduce(&:and)
             end
-            unless last.respond_to?(:infinite?) && last.infinite?
-              binds << build_bind_attribute(column_name, last)
-              last = Arel::Nodes::BindParam.new
-            end
-
-            result[column_name] = RangeHandler::RangeWithBinds.new(first, last, value.exclude_end?)
-          when value.is_a?(Relation)
-            binds.concat(value.bound_attributes)
+            queries.reduce(&:or)
           else
-            if can_be_bound?(column_name, value)
-              bind_attribute = build_bind_attribute(column_name, value)
-              if value.is_a?(StatementCache::Substitute) || !bind_attribute.value_for_database.nil?
-                result[column_name] = Arel::Nodes::BindParam.new
-                binds << bind_attribute
-              else
-                result[column_name] = nil
-              end
-            end
+            build(table.arel_attribute(key), value)
           end
         end
-
-        [result, binds]
       end
 
     private
@@ -161,19 +116,6 @@ module ActiveRecord
       def handler_for(object)
         @handlers.detect { |klass, _| klass === object }.last
       end
-
-      def can_be_bound?(column_name, value)
-        case value
-        when Array, Range
-          table.type(column_name).respond_to?(:subtype)
-        else
-          !value.nil? && handler_for(value).is_a?(BasicObjectHandler)
-        end
-      end
-
-      def build_bind_attribute(column_name, value)
-        Relation::QueryAttribute.new(column_name.to_s, value, table.type(column_name))
-      end
   end
 end
 
diff --git a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
index 85ec7d1428..ad617365fc 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -19,7 +19,11 @@ module ActiveRecord
           case values.length
           when 0 then NullPredicate
           when 1 then predicate_builder.build(attribute, values.first)
-          else attribute.in(values)
+          else
+            bind_values = values.map do |v|
+              predicate_builder.build_bind_attribute(attribute.name, v)
+            end
+            attribute.in(bind_values)
           end
 
         unless nils.empty?
@@ -31,8 +35,6 @@ module ActiveRecord
         array_predicates.inject(&:or)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :predicate_builder
diff --git a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
index 632c68a103..112821135f 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
@@ -11,8 +11,6 @@ module ActiveRecord
         predicate_builder.build(attribute, value.id)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :predicate_builder
diff --git a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
index a17cf30ffd..34db266f05 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
@@ -3,9 +3,18 @@
 module ActiveRecord
   class PredicateBuilder
     class BasicObjectHandler # :nodoc:
+      def initialize(predicate_builder)
+        @predicate_builder = predicate_builder
+      end
+
       def call(attribute, value)
-        attribute.eq(value)
+        bind = predicate_builder.build_bind_attribute(attribute.name, value)
+        attribute.eq(bind)
       end
+
+      protected
+
+        attr_reader :predicate_builder
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
index 072e238306..6d16579708 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
@@ -3,25 +3,39 @@
 module ActiveRecord
   class PredicateBuilder
     class RangeHandler # :nodoc:
-      RangeWithBinds = Struct.new(:begin, :end, :exclude_end?)
+      class RangeWithBinds < Struct.new(:begin, :end)
+        def exclude_end?
+          false
+        end
+      end
+
+      def initialize(predicate_builder)
+        @predicate_builder = predicate_builder
+      end
 
       def call(attribute, value)
+        begin_bind = predicate_builder.build_bind_attribute(attribute.name, value.begin)
+        end_bind = predicate_builder.build_bind_attribute(attribute.name, value.end)
         if value.begin.respond_to?(:infinite?) && value.begin.infinite?
           if value.end.respond_to?(:infinite?) && value.end.infinite?
             attribute.not_in([])
           elsif value.exclude_end?
-            attribute.lt(value.end)
+            attribute.lt(end_bind)
           else
-            attribute.lteq(value.end)
+            attribute.lteq(end_bind)
           end
         elsif value.end.respond_to?(:infinite?) && value.end.infinite?
-          attribute.gteq(value.begin)
+          attribute.gteq(begin_bind)
         elsif value.exclude_end?
-          attribute.gteq(value.begin).and(attribute.lt(value.end))
+          attribute.gteq(begin_bind).and(attribute.lt(end_bind))
         else
-          attribute.between(value)
+          attribute.between(RangeWithBinds.new(begin_bind, end_bind))
         end
       end
+
+      protected
+
+        attr_reader :predicate_builder
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/query_attribute.rb b/activerecord/lib/active_record/relation/query_attribute.rb
index e6883acd90..5a9a7fd432 100644
--- a/activerecord/lib/active_record/relation/query_attribute.rb
+++ b/activerecord/lib/active_record/relation/query_attribute.rb
@@ -16,6 +16,11 @@ module ActiveRecord
       def with_cast_value(value)
         QueryAttribute.new(name, value, type)
       end
+
+      def nil?
+        !value_before_type_cast.is_a?(StatementCache::Substitute) &&
+          (value_before_type_cast.nil? || value_for_database.nil?)
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index e2af62873c..812c8e7e3f 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -76,31 +76,6 @@ module ActiveRecord
       CODE
     end
 
-    def bound_attributes
-      if limit_value
-        limit_bind = Attribute.with_cast_value(
-          "LIMIT".freeze,
-          connection.sanitize_limit(limit_value),
-          Type.default_value,
-        )
-      end
-      if offset_value
-        offset_bind = Attribute.with_cast_value(
-          "OFFSET".freeze,
-          offset_value.to_i,
-          Type.default_value,
-        )
-      end
-      connection.combine_bind_parameters(
-        from_clause: from_clause.binds,
-        join_clause: arel.bind_values,
-        where_clause: where_clause.binds,
-        having_clause: having_clause.binds,
-        limit: limit_bind,
-        offset: offset_bind,
-      )
-    end
-
     alias extensions extending_values
 
     # Specify relationships to be included in the result set. For
@@ -952,8 +927,22 @@ module ActiveRecord
 
         arel.where(where_clause.ast) unless where_clause.empty?
         arel.having(having_clause.ast) unless having_clause.empty?
-        arel.take(Arel::Nodes::BindParam.new) if limit_value
-        arel.skip(Arel::Nodes::BindParam.new) if offset_value
+        if limit_value
+          limit_attribute = Attribute.with_cast_value(
+            "LIMIT".freeze,
+            connection.sanitize_limit(limit_value),
+            Type.default_value,
+          )
+          arel.take(Arel::Nodes::BindParam.new(limit_attribute))
+        end
+        if offset_value
+          offset_attribute = Attribute.with_cast_value(
+            "OFFSET".freeze,
+            offset_value.to_i,
+            Type.default_value,
+          )
+          arel.skip(Arel::Nodes::BindParam.new(offset_attribute))
+        end
         arel.group(*arel_columns(group_values.uniq.reject(&:blank?))) unless group_values.empty?
 
         build_order(arel)
@@ -1029,7 +1018,6 @@ module ActiveRecord
 
         join_infos.each do |info|
           info.joins.each { |join| manager.from(join) }
-          manager.bind_values.concat info.binds
         end
 
         manager.join_sources.concat(join_list)
diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index 0b4c7b7dfa..ef2bca9155 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -3,31 +3,26 @@
 module ActiveRecord
   class Relation
     class WhereClause # :nodoc:
-      attr_reader :binds
-
       delegate :any?, :empty?, to: :predicates
 
-      def initialize(predicates, binds)
+      def initialize(predicates)
         @predicates = predicates
-        @binds = binds
       end
 
       def +(other)
         WhereClause.new(
           predicates + other.predicates,
-          binds + other.binds,
         )
       end
 
       def merge(other)
         WhereClause.new(
           predicates_unreferenced_by(other) + other.predicates,
-          non_conflicting_binds(other) + other.binds,
         )
       end
 
       def except(*columns)
-        WhereClause.new(*except_predicates_and_binds(columns))
+        WhereClause.new(except_predicates(columns))
       end
 
       def or(other)
@@ -38,7 +33,6 @@ module ActiveRecord
         else
           WhereClause.new(
             [ast.or(other.ast)],
-            binds + other.binds
           )
         end
       end
@@ -51,17 +45,10 @@ module ActiveRecord
           end
         end
 
-        binds = self.binds.map { |attr| [attr.name, attr.value] }.to_h
-
         equalities.map { |node|
           name = node.left.name.to_s
-          [name, binds.fetch(name) {
-            case node.right
-            when Array then node.right.map(&:val)
-            when Arel::Nodes::Casted, Arel::Nodes::Quoted
-              node.right.val
-            end
-          }]
+          value = extract_node_value(node.right)
+          [name, value]
         }.to_h
       end
 
@@ -71,20 +58,17 @@ module ActiveRecord
 
       def ==(other)
         other.is_a?(WhereClause) &&
-          predicates == other.predicates &&
-          binds == other.binds
+          predicates == other.predicates
       end
 
       def invert
-        WhereClause.new(inverted_predicates, binds)
+        WhereClause.new(inverted_predicates)
       end
 
       def self.empty
-        @empty ||= new([], [])
+        @empty ||= new([])
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :predicates
@@ -108,12 +92,6 @@ module ActiveRecord
           node.respond_to?(:operator) && node.operator == :==
         end
 
-        def non_conflicting_binds(other)
-          conflicts = referenced_columns & other.referenced_columns
-          conflicts.map! { |node| node.name.to_s }
-          binds.reject { |attr| conflicts.include?(attr.name) }
-        end
-
         def inverted_predicates
           predicates.map { |node| invert_predicate(node) }
         end
@@ -133,44 +111,22 @@ module ActiveRecord
           end
         end
 
-        def except_predicates_and_binds(columns)
-          except_binds = []
-          binds_index = 0
-
-          predicates = self.predicates.reject do |node|
-            binds_contains = node.grep(Arel::Nodes::BindParam).size if node.is_a?(Arel::Nodes::Node)
-
-            except = \
-              case node
-              when Arel::Nodes::Between, Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual, Arel::Nodes::LessThan, Arel::Nodes::LessThanOrEqual, Arel::Nodes::GreaterThan, Arel::Nodes::GreaterThanOrEqual
-                subrelation = (node.left.kind_of?(Arel::Attributes::Attribute) ? node.left : node.right)
-                columns.include?(subrelation.name.to_s)
-              end
-
-            if except && binds_contains > 0
-              (binds_index...(binds_index + binds_contains)).each do |i|
-                except_binds[i] = true
-              end
+        def except_predicates(columns)
+          self.predicates.reject do |node|
+            case node
+            when Arel::Nodes::Between, Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual, Arel::Nodes::LessThan, Arel::Nodes::LessThanOrEqual, Arel::Nodes::GreaterThan, Arel::Nodes::GreaterThanOrEqual
+              subrelation = (node.left.kind_of?(Arel::Attributes::Attribute) ? node.left : node.right)
+              columns.include?(subrelation.name.to_s)
             end
-
-            binds_index += binds_contains if binds_contains
-
-            except
           end
-
-          binds = self.binds.reject.with_index do |_, i|
-            except_binds[i]
-          end
-
-          [predicates, binds]
         end
 
         def predicates_with_wrapped_sql_literals
           non_empty_predicates.map do |node|
-            if Arel::Nodes::Equality === node
-              node
-            else
+            case node
+            when Arel::Nodes::SqlLiteral, ::String
               wrap_sql_literal(node)
+            else node
             end
           end
         end
@@ -186,6 +142,22 @@ module ActiveRecord
           end
           Arel::Nodes::Grouping.new(node)
         end
+
+        def extract_node_value(node)
+          case node
+          when Array
+            node.map { |v| extract_node_value(v) }
+          when Arel::Nodes::Casted, Arel::Nodes::Quoted
+            node.val
+          when Arel::Nodes::BindParam
+            value = node.value
+            if value.respond_to?(:value_before_type_cast)
+              value.value_before_type_cast
+            else
+              value
+            end
+          end
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index 4a0868314d..1374785354 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -17,63 +17,19 @@ module ActiveRecord
           attributes = klass.send(:expand_hash_conditions_for_aggregates, attributes)
           attributes.stringify_keys!
 
-          if perform_case_sensitive?(options = other.last)
-            parts, binds = build_for_case_sensitive(attributes, options)
-          else
-            attributes, binds = predicate_builder.create_binds(attributes)
-            parts = predicate_builder.build_from_hash(attributes)
-          end
+          parts = predicate_builder.build_from_hash(attributes)
         when Arel::Nodes::Node
           parts = [opts]
         else
           raise ArgumentError, "Unsupported argument type: #{opts} (#{opts.class})"
         end
 
-        WhereClause.new(parts, binds || [])
+        WhereClause.new(parts)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :klass, :predicate_builder
-
-      private
-
-        def perform_case_sensitive?(options)
-          options && options.key?(:case_sensitive)
-        end
-
-        def build_for_case_sensitive(attributes, options)
-          parts, binds = [], []
-          table = klass.arel_table
-
-          attributes.each do |attribute, value|
-            if reflection = klass._reflect_on_association(attribute)
-              attribute = reflection.foreign_key.to_s
-              value = value[reflection.klass.primary_key] unless value.nil?
-            end
-
-            if value.nil?
-              parts << table[attribute].eq(value)
-            else
-              column = klass.column_for_attribute(attribute)
-
-              binds << predicate_builder.send(:build_bind_attribute, attribute, value)
-              value = Arel::Nodes::BindParam.new
-
-              predicate = if options[:case_sensitive]
-                klass.connection.case_sensitive_comparison(table, attribute, column, value)
-              else
-                klass.connection.case_insensitive_comparison(table, attribute, column, value)
-              end
-
-              parts << predicate
-            end
-          end
-
-          [parts, binds]
-        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/statement_cache.rb b/activerecord/lib/active_record/statement_cache.rb
index b03ff9bc6c..db7e0c8a04 100644
--- a/activerecord/lib/active_record/statement_cache.rb
+++ b/activerecord/lib/active_record/statement_cache.rb
@@ -41,18 +41,20 @@ module ActiveRecord
     end
 
     class PartialQuery < Query # :nodoc:
-      def initialize(values)
-        @values = values
-        @indexes = values.each_with_index.find_all { |thing, i|
-          Arel::Nodes::BindParam === thing
-        }.map(&:last)
+      def initialize(arel)
+        @arel = arel
       end
 
       def sql_for(binds, connection)
-        val = @values.dup
-        casted_binds = binds.map(&:value_for_database)
-        @indexes.each { |i| val[i] = connection.quote(casted_binds.shift) }
-        val.join
+        val = @arel.dup
+        val.grep(Arel::Nodes::BindParam) do |node|
+          node.value = binds.shift
+          if binds.empty?
+            break
+          end
+        end
+        sql, _ = connection.visitor.accept(val, connection.send(:collector)).value
+        sql
       end
     end
 
@@ -90,9 +92,9 @@ module ActiveRecord
     attr_reader :bind_map, :query_builder
 
     def self.create(connection, block = Proc.new)
-      relation      = block.call Params.new
-      bind_map      = BindMap.new relation.bound_attributes
-      query_builder = connection.cacheable_query(self, relation.arel)
+      relation = block.call Params.new
+      query_builder, binds = connection.cacheable_query(self, relation.arel)
+      bind_map = BindMap.new(binds)
       new query_builder, bind_map
     end
 
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 3a110b461d..4f5b157af9 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -52,7 +52,37 @@ module ActiveRecord
       end
 
       def build_relation(klass, attribute, value)
-        klass.unscoped.where!({ attribute => value }, options)
+        if reflection = klass._reflect_on_association(attribute)
+          attribute = reflection.foreign_key
+          value = value.attributes[reflection.klass.primary_key] unless value.nil?
+        end
+
+        if value.nil?
+          return klass.unscoped.where!(attribute => value)
+        end
+
+        # the attribute may be an aliased attribute
+        if klass.attribute_alias?(attribute)
+          attribute = klass.attribute_alias(attribute)
+        end
+
+        attribute_name = attribute.to_s
+
+        table = klass.arel_table
+        column = klass.columns_hash[attribute_name]
+        cast_type = klass.type_for_attribute(attribute_name)
+
+        value = Relation::QueryAttribute.new(attribute_name, value, cast_type)
+        comparison = if !options[:case_sensitive]
+          # 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.tap do |scope|
+          parts = [comparison]
+          scope.where_clause += Relation::WhereClause.new(parts)
+        end
       end
 
       def scope_relation(record, relation)