Except table_name from column objects

The `table_name` was added at #23677 to detect whether serial column or
not correctly.

We can do that detection before initialize column object, it makes
column object size smaller, and it probably helps column object
de-duplication.

activerecord/lib/active_record/connection_adapters/column.rb

@@ -5,7 +5,7 @@ module ActiveRecord
   module ConnectionAdapters
     # An abstract definition of a column in a table.
     class Column
-      attr_reader :name, :default, :sql_type_metadata, :null, :table_name, :default_function, :collation, :comment
+      attr_reader :name, :default, :sql_type_metadata, :null, :default_function, :collation, :comment
 
       delegate :precision, :scale, :limit, :type, :sql_type, to: :sql_type_metadata, allow_nil: true
 
@@ -15,9 +15,8 @@ module ActiveRecord
       # +default+ is the type-casted default value, such as +new+ in <tt>sales_stage varchar(20) default 'new'</tt>.
       # +sql_type_metadata+ is various information about the type of the column
       # +null+ determines if this column allows +NULL+ values.
-      def initialize(name, default, sql_type_metadata = nil, null = true, table_name = nil, default_function = nil, collation = nil, comment: nil, **)
+      def initialize(name, default, sql_type_metadata = nil, null = true, default_function = nil, collation: nil, comment: nil, **)
         @name = name.freeze
-        @table_name = table_name
         @sql_type_metadata = sql_type_metadata
         @null = null
         @default = default
@@ -44,7 +43,6 @@ module ActiveRecord
 
       def init_with(coder)
         @name = coder["name"]
-        @table_name = coder["table_name"]
         @sql_type_metadata = coder["sql_type_metadata"]
         @null = coder["null"]
         @default = coder["default"]
@@ -55,7 +53,6 @@ module ActiveRecord
 
       def encode_with(coder)
         coder["name"] = @name
-        coder["table_name"] = @table_name
         coder["sql_type_metadata"] = @sql_type_metadata
         coder["null"] = @null
         coder["default"] = @default
@@ -77,7 +74,7 @@ module ActiveRecord
       protected
 
         def attributes_for_hash
-          [self.class, name, default, sql_type_metadata, null, table_name, default_function, collation]
+          [self.class, name, default, sql_type_metadata, null, default_function, collation, comment]
         end
     end
 

activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb

@@ -55,7 +55,7 @@ module ActiveRecord
           end
 
           def schema_collation(column)
-            if column.collation && table_name = column.table_name
+            if column.collation
               @table_collation_cache ||= {}
               @table_collation_cache[table_name] ||=
                 @connection.exec_query("SHOW TABLE STATUS LIKE #{@connection.quote(table_name)}", "SCHEMA").first["Collation"]
@@ -65,13 +65,13 @@ module ActiveRecord
 
           def extract_expression_for_virtual_column(column)
             if @connection.mariadb? && @connection.database_version < "10.2.5"
-              create_table_info = @connection.send(:create_table_info, column.table_name)
+              create_table_info = @connection.send(:create_table_info, table_name)
               column_name = @connection.quote_column_name(column.name)
               if %r/#{column_name} #{Regexp.quote(column.sql_type)}(?: COLLATE \w+)? AS \((?<expression>.+?)\) #{column.extra}/ =~ create_table_info
                 $~[:expression].inspect
               end
             else
-              scope = @connection.send(:quoted_scope, column.table_name)
+              scope = @connection.send(:quoted_scope, table_name)
               column_name = @connection.quote(column.name)
               sql = "SELECT generation_expression FROM information_schema.columns" \
                     " WHERE table_schema = #{scope[:schema]}" \

activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb

@@ -174,9 +174,8 @@ module ActiveRecord
               default,
               type_metadata,
               field[:Null] == "YES",
-              table_name,
               default_function,
-              field[:Collation],
+              collation: field[:Collation],
               comment: field[:Comment].presence
             )
           end

activerecord/lib/active_record/connection_adapters/postgresql/column.rb

@@ -2,42 +2,21 @@
 
 module ActiveRecord
   module ConnectionAdapters
-    # PostgreSQL-specific extensions to column definitions in a table.
-    class PostgreSQLColumn < Column #:nodoc:
+    module PostgreSQL
+      class Column < ConnectionAdapters::Column # :nodoc:
         delegate :array, :oid, :fmod, to: :sql_type_metadata
         alias :array? :array
 
-      def initialize(*, max_identifier_length: 63, **)
+        def initialize(*, serial: nil, **)
           super
-        @max_identifier_length = max_identifier_length
+          @serial = serial
         end
 
         def serial?
-        return unless default_function
-
-        if %r{\Anextval\('"?(?<sequence_name>.+_(?<suffix>seq\d*))"?'::regclass\)\z} =~ default_function
-          sequence_name_from_parts(table_name, name, suffix) == sequence_name
-        end
-      end
-
-      private
-        attr_reader :max_identifier_length
-
-        def sequence_name_from_parts(table_name, column_name, suffix)
-          over_length = [table_name, column_name, suffix].map(&:length).sum + 2 - max_identifier_length
-
-          if over_length > 0
-            column_name_length = [(max_identifier_length - suffix.length - 2) / 2, column_name.length].min
-            over_length -= column_name.length - column_name_length
-            column_name = column_name[0, column_name_length - [over_length, 0].min]
-          end
-
-          if over_length > 0
-            table_name = table_name[0, table_name.length - over_length]
-          end
-
-          "#{table_name}_#{column_name}_#{suffix}"
+          @serial
         end
       end
     end
+    PostgreSQLColumn = PostgreSQL::Column # :nodoc:
+  end
 end

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -650,16 +650,19 @@ module ActiveRecord
             default_value = extract_value_from_default(default)
             default_function = extract_default_function(default_value, default)
 
-            PostgreSQLColumn.new(
+            if match = default_function&.match(/\Anextval\('"?(?<sequence_name>.+_(?<suffix>seq\d*))"?'::regclass\)\z/)
+              serial = sequence_name_from_parts(table_name, column_name, match[:suffix]) == match[:sequence_name]
+            end
+
+            PostgreSQL::Column.new(
               column_name,
               default_value,
               type_metadata,
               !notnull,
-              table_name,
               default_function,
-              collation,
+              collation: collation,
               comment: comment.presence,
-              max_identifier_length: max_identifier_length
+              serial: serial
             )
           end
 
@@ -675,6 +678,22 @@ module ActiveRecord
             PostgreSQLTypeMetadata.new(simple_type, oid: oid, fmod: fmod)
           end
 
+          def sequence_name_from_parts(table_name, column_name, suffix)
+            over_length = [table_name, column_name, suffix].sum(&:length) + 2 - max_identifier_length
+
+            if over_length > 0
+              column_name_length = [(max_identifier_length - suffix.length - 2) / 2, column_name.length].min
+              over_length -= column_name.length - column_name_length
+              column_name = column_name[0, column_name_length - [over_length, 0].min]
+            end
+
+            if over_length > 0
+              table_name = table_name[0, table_name.length - over_length]
+            end
+
+            "#{table_name}_#{column_name}_#{suffix}"
+          end
+
           def extract_foreign_key_action(specifier)
             case specifier
             when "c"; :cascade

activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb

@@ -105,7 +105,7 @@ module ActiveRecord
               end
 
             type_metadata = fetch_type_metadata(field["type"])
-            Column.new(field["name"], default, type_metadata, field["notnull"].to_i == 0, table_name, nil, field["collation"])
+            Column.new(field["name"], default, type_metadata, field["notnull"].to_i == 0, collation: field["collation"])
           end
 
           def data_source_sql(name = nil, type: nil)

activerecord/lib/active_record/schema_dumper.rb

@@ -47,6 +47,7 @@ module ActiveRecord
     end
 
     private
+      attr_accessor :table_name
 
       def initialize(connection, options = {})
         @connection = connection
@@ -110,6 +111,8 @@ HEADER
       def table(table, stream)
         columns = @connection.columns(table)
         begin
+          self.table_name = table
+
           tbl = StringIO.new
 
           # first dump primary key column
@@ -159,6 +162,8 @@ HEADER
           stream.puts "# Could not dump table #{table.inspect} because of following #{e.class}"
           stream.puts "#   #{e.message}"
           stream.puts
+        ensure
+          self.table_name = nil
         end
       end