Merge branch 'master' into activestorage-guide

17 files changed, 345 insertions, 139 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index be2f625d74..0594b4b485 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -6,7 +6,7 @@ module ActiveRecord
     # this type are typically created and returned by methods in database
     # adapters. e.g. ActiveRecord::ConnectionAdapters::MySQL::SchemaStatements#indexes
     class IndexDefinition # :nodoc:
-      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :where, :type, :using, :comment
+      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :opclasses, :where, :type, :using, :comment
 
       def initialize(
         table, name,
@@ -14,6 +14,7 @@ module ActiveRecord
         columns = [],
         lengths: {},
         orders: {},
+        opclasses: {},
         where: nil,
         type: nil,
         using: nil,
@@ -23,13 +24,23 @@ module ActiveRecord
         @name = name
         @unique = unique
         @columns = columns
-        @lengths = lengths
-        @orders = orders
+        @lengths = concise_options(lengths)
+        @orders = concise_options(orders)
+        @opclasses = concise_options(opclasses)
         @where = where
         @type = type
         @using = using
         @comment = comment
       end
+
+      private
+        def concise_options(options)
+          if columns.size == options.size && options.values.uniq.size == 1
+            options.values.first
+          else
+            options
+          end
+        end
     end
 
     # Abstract representation of a column definition. Instances of this type
@@ -85,6 +96,11 @@ module ActiveRecord
         options[:primary_key] != default_primary_key
       end
 
+      def validate?
+        options.fetch(:validate, true)
+      end
+      alias validated? validate?
+
       def defined_for?(to_table_ord = nil, to_table: nil, **options)
         if to_table_ord
           self.to_table == to_table_ord.to_s
@@ -204,6 +220,7 @@ module ActiveRecord
         :decimal,
         :float,
         :integer,
+        :json,
         :string,
         :text,
         :time,
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 9b7345f7c3..4f58b0242c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -600,7 +600,7 @@ module ActiveRecord
       # to provide these in a migration's +change+ method so it can be reverted.
       # In that case, +type+ and +options+ will be used by #add_column.
       def remove_column(table_name, column_name, type = nil, options = {})
-        execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}"
+        execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, options)}"
       end
 
       # Changes the column's definition according to the new options.
@@ -738,6 +738,28 @@ module ActiveRecord
       #
       # Note: only supported by PostgreSQL and MySQL
       #
+      # ====== Creating an index with a specific operator class
+      #
+      #   add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops })
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL
+      #
+      # Note: only supported by PostgreSQL
+      #
       # ====== Creating an index with a specific type
       #
       #   add_index(:developers, :name, type: :fulltext)
@@ -942,6 +964,8 @@ module ActiveRecord
       #   Action that happens <tt>ON DELETE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
       # [<tt>:on_update</tt>]
       #   Action that happens <tt>ON UPDATE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
+      # [<tt>:validate</tt>]
+      #   (Postgres only) Specify whether or not the constraint should be validated. Defaults to +true+.
       def add_foreign_key(from_table, to_table, options = {})
         return unless supports_foreign_keys?
 
@@ -1120,7 +1144,7 @@ module ActiveRecord
       def add_index_options(table_name, column_name, comment: nil, **options) # :nodoc:
         column_names = index_column_names(column_name)
 
-        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type)
+        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type, :opclass)
 
         index_type = options[:type].to_s if options.key?(:type)
         index_type ||= options[:unique] ? "UNIQUE" : ""
@@ -1173,20 +1197,22 @@ module ActiveRecord
         end
 
         def add_index_sort_order(quoted_columns, **options)
-          if order = options[:order]
-            case order
-            when Hash
-              order = order.symbolize_keys
-              quoted_columns.each { |name, column| column << " #{order[name].upcase}" if order[name].present? }
-            when String
-              quoted_columns.each { |name, column| column << " #{order.upcase}" if order.present? }
-            end
+          orders = options_for_index_columns(options[:order])
+          quoted_columns.each do |name, column|
+            column << " #{orders[name].upcase}" if orders[name].present?
           end
+        end
 
-          quoted_columns
+        def options_for_index_columns(options)
+          if options.is_a?(Hash)
+            options.symbolize_keys
+          else
+            Hash.new { |hash, column| hash[column] = options }
+          end
         end
 
-        # Overridden by the MySQL adapter for supporting index lengths
+        # Overridden by the MySQL adapter for supporting index lengths and by
+        # the PostgreSQL adapter for supporting operator classes.
         def add_options_for_index_columns(quoted_columns, **options)
           if supports_index_sort_order?
             quoted_columns = add_index_sort_order(quoted_columns, options)
@@ -1340,6 +1366,20 @@ module ActiveRecord
           options.is_a?(Hash) && options.key?(:name) && options.except(:name, :algorithm).empty?
         end
 
+        def add_column_for_alter(table_name, column_name, type, options = {})
+          td = create_table_definition(table_name)
+          cd = td.new_column_definition(column_name, type, options)
+          schema_creation.accept(AddColumnDefinition.new(cd))
+        end
+
+        def remove_column_for_alter(table_name, column_name, type = nil, options = {})
+          "DROP COLUMN #{quote_column_name(column_name)}"
+        end
+
+        def remove_columns_for_alter(table_name, *column_names)
+          column_names.map { |column_name| remove_column_for_alter(table_name, column_name) }
+        end
+
         def insert_versions_sql(versions)
           sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 8993c517a6..fc80d332f9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -272,6 +272,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support creating invalid constraints?
+      def supports_validate_constraints?
+        false
+      end
+
       # Does this adapter support creating foreign key constraints
       # in the same statement as creating the table?
       def supports_foreign_keys_in_create?
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 ede8a9c1e2..479131caad 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -299,7 +299,7 @@ module ActiveRecord
       def bulk_change_table(table_name, operations) #:nodoc:
         sqls = operations.flat_map do |command, args|
           table, arguments = args.shift, args
-          method = :"#{command}_sql"
+          method = :"#{command}_for_alter"
 
           if respond_to?(method, true)
             send(method, table, *arguments)
@@ -372,11 +372,11 @@ module ActiveRecord
       end
 
       def change_column(table_name, column_name, type, options = {}) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_sql(table_name, column_name, type, options)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_for_alter(table_name, column_name, type, options)}")
       end
 
       def rename_column(table_name, column_name, new_column_name) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_sql(table_name, column_name, new_column_name)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_for_alter(table_name, column_name, new_column_name)}")
         rename_column_indexes(table_name, column_name, new_column_name)
       end
 
@@ -605,25 +605,6 @@ module ActiveRecord
           end
         end
 
-        def add_index_length(quoted_columns, **options)
-          if length = options[:length]
-            case length
-            when Hash
-              length = length.symbolize_keys
-              quoted_columns.each { |name, column| column << "(#{length[name]})" if length[name].present? }
-            when Integer
-              quoted_columns.each { |name, column| column << "(#{length})" }
-            end
-          end
-
-          quoted_columns
-        end
-
-        def add_options_for_index_columns(quoted_columns, **options)
-          quoted_columns = add_index_length(quoted_columns, options)
-          super
-        end
-
         # See https://dev.mysql.com/doc/refman/5.7/en/error-messages-server.html
         ER_DUP_ENTRY            = 1062
         ER_NOT_NULL_VIOLATION   = 1048
@@ -671,13 +652,7 @@ module ActiveRecord
           end
         end
 
-        def add_column_sql(table_name, column_name, type, options = {})
-          td = create_table_definition(table_name)
-          cd = td.new_column_definition(column_name, type, options)
-          schema_creation.accept(AddColumnDefinition.new(cd))
-        end
-
-        def change_column_sql(table_name, column_name, type, options = {})
+        def change_column_for_alter(table_name, column_name, type, options = {})
           column = column_for(table_name, column_name)
           type ||= column.sql_type
 
@@ -698,7 +673,7 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def rename_column_sql(table_name, column_name, new_column_name)
+        def rename_column_for_alter(table_name, column_name, new_column_name)
           column  = column_for(table_name, column_name)
           options = {
             default: column.default,
@@ -712,31 +687,23 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def remove_column_sql(table_name, column_name, type = nil, options = {})
-          "DROP #{quote_column_name(column_name)}"
-        end
-
-        def remove_columns_sql(table_name, *column_names)
-          column_names.map { |column_name| remove_column_sql(table_name, column_name) }
-        end
-
-        def add_index_sql(table_name, column_name, options = {})
+        def add_index_for_alter(table_name, column_name, options = {})
           index_name, index_type, index_columns, _, index_algorithm, index_using = add_index_options(table_name, column_name, options)
           index_algorithm[0, 0] = ", " if index_algorithm.present?
           "ADD #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} (#{index_columns})#{index_algorithm}"
         end
 
-        def remove_index_sql(table_name, options = {})
+        def remove_index_for_alter(table_name, options = {})
           index_name = index_name_for_remove(table_name, options)
           "DROP INDEX #{quote_column_name(index_name)}"
         end
 
-        def add_timestamps_sql(table_name, options = {})
-          [add_column_sql(table_name, :created_at, :datetime, options), add_column_sql(table_name, :updated_at, :datetime, options)]
+        def add_timestamps_for_alter(table_name, options = {})
+          [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
         end
 
-        def remove_timestamps_sql(table_name, options = {})
-          [remove_column_sql(table_name, :updated_at), remove_column_sql(table_name, :created_at)]
+        def remove_timestamps_for_alter(table_name, options = {})
+          [remove_column_for_alter(table_name, :updated_at), remove_column_for_alter(table_name, :created_at)]
         end
 
         # MySQL is too stupid to create a temporary table for use subquery, so we have
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
index da25e4863c..2ed4ad16ae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -32,10 +32,6 @@ module ActiveRecord
           args.each { |name| column(name, :longtext, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def unsigned_integer(*args, **options)
           args.each { |name| column(name, :unsigned_integer, options) }
         end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index a15c7d1787..ce50590651 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -22,23 +22,26 @@ module ActiveRecord
                   index_using = mysql_index_type
                 end
 
-                indexes << IndexDefinition.new(
+                indexes << [
                   row[:Table],
                   row[:Key_name],
                   row[:Non_unique].to_i == 0,
+                  [],
+                  lengths: {},
+                  orders: {},
                   type: index_type,
                   using: index_using,
                   comment: row[:Index_comment].presence
-                )
+                ]
               end
 
-              indexes.last.columns << row[:Column_name]
-              indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
-              indexes.last.orders.merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
+              indexes.last[-2] << row[:Column_name]
+              indexes.last[-1][:lengths].merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
+              indexes.last[-1][:orders].merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
             end
           end
 
-          indexes
+          indexes.map { |index| IndexDefinition.new(*index) }
         end
 
         def remove_column(table_name, column_name, type = nil, options = {})
@@ -103,6 +106,18 @@ module ActiveRecord
             super unless specifier == "RESTRICT"
           end
 
+          def add_index_length(quoted_columns, **options)
+            lengths = options_for_index_columns(options[:length])
+            quoted_columns.each do |name, column|
+              column << "(#{lengths[name]})" if lengths[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_length(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
index 59f661da25..8e381a92cf 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
@@ -5,6 +5,18 @@ module ActiveRecord
     module PostgreSQL
       class SchemaCreation < AbstractAdapter::SchemaCreation # :nodoc:
         private
+          def visit_AlterTable(o)
+            super << o.constraint_validations.map { |fk| visit_ValidateConstraint fk }.join(" ")
+          end
+
+          def visit_AddForeignKey(o)
+            super.dup.tap { |sql| sql << " NOT VALID" unless o.validate? }
+          end
+
+          def visit_ValidateConstraint(name)
+            "VALIDATE CONSTRAINT #{quote_column_name(name)}"
+          end
+
           def add_column_options!(sql, options)
             if options[:collation]
               sql << " COLLATE \"#{options[:collation]}\""
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
index 75622eb304..6047217fcd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
@@ -95,10 +95,6 @@ module ActiveRecord
           args.each { |name| column(name, :int8range, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def jsonb(*args, **options)
           args.each { |name| column(name, :jsonb, options) }
         end
@@ -192,6 +188,19 @@ module ActiveRecord
       class Table < ActiveRecord::ConnectionAdapters::Table
         include ColumnMethods
       end
+
+      class AlterTable < ActiveRecord::ConnectionAdapters::AlterTable
+        attr_reader :constraint_validations
+
+        def initialize(td)
+          super
+          @constraint_validations = []
+        end
+
+        def validate_constraint(name)
+          @constraint_validations << name
+        end
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 846e721983..bf5fbb30e1 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -87,10 +87,7 @@ module ActiveRecord
 
           result = query(<<-SQL, "SCHEMA")
             SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid,
-                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment,
-            (SELECT COUNT(*) FROM pg_opclass o
-               JOIN (SELECT unnest(string_to_array(d.indclass::text, ' '))::int oid) c
-                 ON o.oid = c.oid WHERE o.opcdefault = 'f')
+                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment
             FROM pg_class t
             INNER JOIN pg_index d ON t.oid = d.indrelid
             INNER JOIN pg_class i ON d.indexrelid = i.oid
@@ -109,11 +106,13 @@ module ActiveRecord
             inddef = row[3]
             oid = row[4]
             comment = row[5]
-            opclass = row[6]
 
             using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/).flatten
 
-            if indkey.include?(0) || opclass > 0
+            orders = {}
+            opclasses = {}
+
+            if indkey.include?(0)
               columns = expressions
             else
               columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
@@ -123,10 +122,12 @@ module ActiveRecord
                 AND a.attnum IN (#{indkey.join(",")})
               SQL
 
-              # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
-              orders = Hash[
-                expressions.scan(/(\w+) DESC/).flatten.map { |order_column| [order_column, :desc] }
-              ]
+              # add info on sort order (only desc order is explicitly specified, asc is the default)
+              # and non-default opclasses
+              expressions.scan(/(\w+)(?: (?!DESC)(\w+))?(?: (DESC))?/).each do |column, opclass, desc|
+                opclasses[column] = opclass.to_sym if opclass
+                orders[column] = :desc if desc
+              end
             end
 
             IndexDefinition.new(
@@ -135,6 +136,7 @@ module ActiveRecord
               unique,
               columns,
               orders: orders,
+              opclasses: opclasses,
               where: where,
               using: using.to_sym,
               comment: comment.presence
@@ -392,50 +394,23 @@ module ActiveRecord
 
         def change_column(table_name, column_name, type, options = {}) #:nodoc:
           clear_cache!
-          quoted_table_name = quote_table_name(table_name)
-          quoted_column_name = quote_column_name(column_name)
-          sql_type = type_to_sql(type, options)
-          sql = "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
-          if options[:collation]
-            sql << " COLLATE \"#{options[:collation]}\""
-          end
-          if options[:using]
-            sql << " USING #{options[:using]}"
-          elsif options[:cast_as]
-            cast_as_type = type_to_sql(options[:cast_as], options)
-            sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
-          end
-          execute sql
-
-          change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
-          change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
-          change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          sqls, procs = change_column_for_alter(table_name, column_name, type, options)
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{sqls.join(", ")}"
+          procs.each(&:call)
         end
 
         # Changes the default value of a table column.
         def change_column_default(table_name, column_name, default_or_changes) # :nodoc:
-          clear_cache!
-          column = column_for(table_name, column_name)
-          return unless column
-
-          default = extract_new_default_value(default_or_changes)
-          alter_column_query = "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} %s"
-          if default.nil?
-            # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
-            # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
-            execute alter_column_query % "DROP DEFAULT"
-          else
-            execute alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
-          end
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_default_for_alter(table_name, column_name, default_or_changes)}"
         end
 
         def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
           clear_cache!
           unless null || default.nil?
             column = column_for(table_name, column_name)
-            execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL") if column
+            execute "UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL" if column
           end
-          execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_null_for_alter(table_name, column_name, null, default)}"
         end
 
         # Adds comment for given table column or drops it if +comment+ is a +nil+
@@ -458,8 +433,8 @@ module ActiveRecord
         end
 
         def add_index(table_name, column_name, options = {}) #:nodoc:
-          index_name, index_type, index_columns, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
-          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns})#{index_options}").tap do
+          index_name, index_type, index_columns_and_opclasses, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
+          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns_and_opclasses})#{index_options}").tap do
             execute "COMMENT ON INDEX #{quote_column_name(index_name)} IS #{quote(comment)}" if comment
           end
         end
@@ -499,7 +474,7 @@ module ActiveRecord
         def foreign_keys(table_name)
           scope = quoted_scope(table_name)
           fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
-            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete
+            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid
             FROM pg_constraint c
             JOIN pg_class t1 ON c.conrelid = t1.oid
             JOIN pg_class t2 ON c.confrelid = t2.oid
@@ -521,6 +496,7 @@ module ActiveRecord
 
             options[:on_delete] = extract_foreign_key_action(row["on_delete"])
             options[:on_update] = extract_foreign_key_action(row["on_update"])
+            options[:validate] = row["valid"]
 
             ForeignKeyDefinition.new(table_name, row["to_table"], options)
           end
@@ -581,6 +557,43 @@ module ActiveRecord
           PostgreSQL::SchemaDumper.create(self, options)
         end
 
+        # Validates the given constraint.
+        #
+        # Validates the constraint named +constraint_name+ on +accounts+.
+        #
+        #   validate_constraint :accounts, :constraint_name
+        def validate_constraint(table_name, constraint_name)
+          return unless supports_validate_constraints?
+
+          at = create_alter_table table_name
+          at.validate_constraint constraint_name
+
+          execute schema_creation.accept(at)
+        end
+
+        # Validates the given foreign key.
+        #
+        # Validates the foreign key on +accounts.branch_id+.
+        #
+        #   validate_foreign_key :accounts, :branches
+        #
+        # Validates the foreign key on +accounts.owner_id+.
+        #
+        #   validate_foreign_key :accounts, column: :owner_id
+        #
+        # Validates the foreign key named +special_fk_name+ on the +accounts+ table.
+        #
+        #   validate_foreign_key :accounts, name: :special_fk_name
+        #
+        # The +options+ hash accepts the same keys as SchemaStatements#add_foreign_key.
+        def validate_foreign_key(from_table, options_or_to_table = {})
+          return unless supports_validate_constraints?
+
+          fk_name_to_validate = foreign_key_for!(from_table, options_or_to_table).name
+
+          validate_constraint from_table, fk_name_to_validate
+        end
+
         private
           def schema_creation
             PostgreSQL::SchemaCreation.new(self)
@@ -590,6 +603,10 @@ module ActiveRecord
             PostgreSQL::TableDefinition.new(*args)
           end
 
+          def create_alter_table(name)
+            PostgreSQL::AlterTable.new create_table_definition(name)
+          end
+
           def new_column_from_field(table_name, field)
             column_name, type, default, notnull, oid, fmod, collation, comment = field
             type_metadata = fetch_type_metadata(column_name, type, oid.to_i, fmod.to_i)
@@ -629,6 +646,66 @@ module ActiveRecord
             end
           end
 
+          def change_column_sql(table_name, column_name, type, options = {})
+            quoted_column_name = quote_column_name(column_name)
+            sql_type = type_to_sql(type, options)
+            sql = "ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
+            if options[:collation]
+              sql << " COLLATE \"#{options[:collation]}\""
+            end
+            if options[:using]
+              sql << " USING #{options[:using]}"
+            elsif options[:cast_as]
+              cast_as_type = type_to_sql(options[:cast_as], options)
+              sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
+            end
+
+            sql
+          end
+
+          def change_column_for_alter(table_name, column_name, type, options = {})
+            sqls = [change_column_sql(table_name, column_name, type, options)]
+            procs = []
+            sqls << change_column_default_for_alter(table_name, column_name, options[:default]) if options.key?(:default)
+            sqls << change_column_null_for_alter(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            procs << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
+
+            [sqls, procs]
+          end
+
+
+          # Changes the default value of a table column.
+          def change_column_default_for_alter(table_name, column_name, default_or_changes) # :nodoc:
+            column = column_for(table_name, column_name)
+            return unless column
+
+            default = extract_new_default_value(default_or_changes)
+            alter_column_query = "ALTER COLUMN #{quote_column_name(column_name)} %s"
+            if default.nil?
+              # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
+              # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
+              alter_column_query % "DROP DEFAULT"
+            else
+              alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
+            end
+          end
+
+          def change_column_null_for_alter(table_name, column_name, null, default = nil) #:nodoc:
+            "ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL"
+          end
+
+          def add_index_opclass(quoted_columns, **options)
+            opclasses = options_for_index_columns(options[:opclass])
+            quoted_columns.each do |name, column|
+              column << " #{opclasses[name]}" if opclasses[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_opclass(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
             scope[:type] ||= "'r','v','m'" # (r)elation/table, (v)iew, (m)aterialized view
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 27011bfe92..23fc69d649 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -142,6 +142,10 @@ module ActiveRecord
         true
       end
 
+      def supports_validate_constraints?
+        true
+      end
+
       def supports_views?
         true
       end
@@ -386,7 +390,6 @@ module ActiveRecord
       end
 
       private
-
         # See https://www.postgresql.org/docs/current/static/errcodes-appendix.html
         VALUE_LIMIT_VIOLATION = "22001"
         NUMERIC_VALUE_OUT_OF_RANGE = "22003"
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index daece2bffd..c72db15ce3 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -70,7 +70,8 @@ module ActiveRecord
         time:         { name: "time" },
         date:         { name: "date" },
         binary:       { name: "blob" },
-        boolean:      { name: "boolean" }
+        boolean:      { name: "boolean" },
+        json:         { name: "json" },
       }
 
       ##
@@ -134,6 +135,10 @@ module ActiveRecord
         true
       end
 
+      def supports_json?
+        true
+      end
+
       def supports_multi_insert?
         sqlite_version >= "3.7.11"
       end
@@ -369,6 +374,10 @@ module ActiveRecord
       end
 
       private
+        def initialize_type_map(m = type_map)
+          super
+          register_class_with_limit m, %r(int)i, SQLite3Integer
+        end
 
         def table_structure(table_name)
           structure = exec_query("PRAGMA table_info(#{quote_table_name(table_name)})", "SCHEMA")
@@ -398,18 +407,21 @@ module ActiveRecord
           options[:id] = false
           create_table(to, options) do |definition|
             @definition = definition
-            @definition.primary_key(from_primary_key) if from_primary_key.present?
+            if from_primary_key.is_a?(Array)
+              @definition.primary_keys from_primary_key
+            end
             columns(from).each do |column|
               column_name = options[:rename] ?
                 (options[:rename][column.name] ||
                  options[:rename][column.name.to_sym] ||
                  column.name) : column.name
-              next if column_name == from_primary_key
 
               @definition.column(column_name, column.type,
                 limit: column.limit, default: column.default,
                 precision: column.precision, scale: column.scale,
-                null: column.null, collation: column.collation)
+                null: column.null, collation: column.collation,
+                primary_key: column_name == from_primary_key
+              )
             end
             yield @definition if block_given?
           end
@@ -422,6 +434,9 @@ module ActiveRecord
         def copy_table_indexes(from, to, rename = {})
           indexes(from).each do |index|
             name = index.name
+            # indexes sqlite creates for internal use start with `sqlite_` and
+            # don't need to be copied
+            next if name.starts_with?("sqlite_")
             if to == "a#{from}"
               name = "t#{name}"
             elsif from == "a#{to}"
@@ -524,6 +539,17 @@ module ActiveRecord
         def configure_connection
           execute("PRAGMA foreign_keys = ON", "SCHEMA")
         end
+
+        class SQLite3Integer < Type::Integer # :nodoc:
+          private
+            def _limit
+              # INTEGER storage class can be stored 8 bytes value.
+              # See https://www.sqlite.org/datatype3.html#storage_classes_and_datatypes
+              limit || 8
+            end
+        end
+
+        ActiveRecord::Type.register(:integer, SQLite3Integer, adapter: :sqlite3)
     end
     ActiveSupport.run_load_hooks(:active_record_sqlite3adapter, SQLite3Adapter)
   end
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 15e9c09ffb..5c10d4ff24 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1045,7 +1045,7 @@ module ActiveRecord
         new(:up, migrations(migrations_paths), nil)
       end
 
-      def get_all_versions(connection = Base.connection)
+      def get_all_versions
         if SchemaMigration.table_exists?
           SchemaMigration.all_versions.map(&:to_i)
         else
@@ -1053,12 +1053,13 @@ module ActiveRecord
         end
       end
 
-      def current_version(connection = Base.connection)
-        get_all_versions(connection).max || 0
+      def current_version(connection = nil)
+        get_all_versions.max || 0
+      rescue ActiveRecord::NoDatabaseError
       end
 
-      def needs_migration?(connection = Base.connection)
-        (migrations(migrations_paths).collect(&:version) - get_all_versions(connection)).size > 0
+      def needs_migration?(connection = nil)
+        (migrations(migrations_paths).collect(&:version) - get_all_versions).size > 0
       end
 
       def any_migrations?
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index c979aaf0a0..bd8c054c28 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -16,6 +16,18 @@ module ActiveRecord
       V5_2 = Current
 
       class V5_1 < V5_2
+        def change_column(table_name, column_name, type, options = {})
+          if adapter_name == "PostgreSQL"
+            clear_cache!
+            sql = connection.send(:change_column_sql, table_name, column_name, type, options)
+            execute "ALTER TABLE #{quote_table_name(table_name)} #{sql}"
+            change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
+            change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          else
+            super
+          end
+        end
       end
 
       class V5_0 < V5_1
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 4e1b05dbf6..a13b0d0181 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -99,7 +99,9 @@ module ActiveRecord
       # for updating all records in a single query.
       def update(id = :all, attributes)
         if id.is_a?(Array)
-          id.map.with_index { |one_id, idx| update(one_id, attributes[idx]) }.compact
+          id.map { |one_id| find(one_id) }.each_with_index { |object, idx|
+            object.update(attributes[idx])
+          }
         elsif id == :all
           all.each { |record| record.update(attributes) }
         else
@@ -112,7 +114,6 @@ module ActiveRecord
           object.update(attributes)
           object
         end
-      rescue RecordNotFound
       end
 
       # Destroy an object (or multiple objects) that has the given id. The object is instantiated first,
@@ -136,11 +137,10 @@ module ActiveRecord
       #   Todo.destroy(todos)
       def destroy(id)
         if id.is_a?(Array)
-          id.map { |one_id| destroy(one_id) }.compact
+          find(id).each(&:destroy)
         else
           find(id).destroy
         end
-      rescue RecordNotFound
       end
 
       # Deletes the row with a primary key matching the +id+ argument, using a
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 9ee8425e1b..4538ed6a5f 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -90,12 +90,15 @@ module ActiveRecord
             filename = File.join(app.config.paths["db"].first, "schema_cache.yml")
 
             if File.file?(filename)
+              current_version = ActiveRecord::Migrator.current_version
+              next if current_version.nil?
+
               cache = YAML.load(File.read(filename))
-              if cache.version == ActiveRecord::Migrator.current_version
+              if cache.version == current_version
                 connection.schema_cache = cache
                 connection_pool.schema_cache = cache.dup
               else
-                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{ActiveRecord::Migrator.current_version}, but the one in the cache is #{cache.version}."
+                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{current_version}, but the one in the cache is #{cache.version}."
               end
             end
           end
diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index 752bb38481..a502713e56 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -47,7 +47,7 @@ module ActiveRecord
       end
 
       def to_h(table_name = nil)
-        equalities = predicates.grep(Arel::Nodes::Equality)
+        equalities = equalities(predicates)
         if table_name
           equalities = equalities.select do |node|
             node.left.relation.name == table_name
@@ -90,6 +90,20 @@ module ActiveRecord
         end
 
       private
+        def equalities(predicates)
+          equalities = []
+
+          predicates.each do |node|
+            case node
+            when Arel::Nodes::Equality
+              equalities << node
+            when Arel::Nodes::And
+              equalities.concat equalities(node.children)
+            end
+          end
+
+          equalities
+        end
 
         def predicates_unreferenced_by(other)
           predicates.reject do |n|
@@ -121,7 +135,7 @@ module ActiveRecord
         end
 
         def except_predicates(columns)
-          self.predicates.reject do |node|
+          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)
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 66f7d29886..16ccba6b6c 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -184,8 +184,9 @@ HEADER
           "name: #{index.name.inspect}",
         ]
         index_parts << "unique: true" if index.unique
-        index_parts << "length: { #{format_options(index.lengths)} }" if index.lengths.present?
-        index_parts << "order: { #{format_options(index.orders)} }" if index.orders.present?
+        index_parts << "length: #{format_index_parts(index.lengths)}" if index.lengths.present?
+        index_parts << "order: #{format_index_parts(index.orders)}" if index.orders.present?
+        index_parts << "opclass: #{format_index_parts(index.opclasses)}" if index.opclasses.present?
         index_parts << "where: #{index.where.inspect}" if index.where
         index_parts << "using: #{index.using.inspect}" if !@connection.default_index_type?(index)
         index_parts << "type: #{index.type.inspect}" if index.type
@@ -231,6 +232,14 @@ HEADER
         options.map { |key, value| "#{key}: #{value.inspect}" }.join(", ")
       end
 
+      def format_index_parts(options)
+        if options.is_a?(Hash)
+          "{ #{format_options(options)} }"
+        else
+          options.inspect
+        end
+      end
+
       def remove_prefix_and_suffix(table)
         prefix = Regexp.escape(@options[:table_name_prefix].to_s)
         suffix = Regexp.escape(@options[:table_name_suffix].to_s)