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.

1 files changed, 32 insertions, 60 deletions

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