fix for #10613 . This PR is still WIP.

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

@@ -86,11 +86,14 @@ def type_cast(value)
 
         class Array < Type
           attr_reader :subtype
+          attr_writer :typecast
           def initialize(subtype)
             @subtype = subtype
+            @typecast = true
           end
 
           def type_cast(value)
+            return value unless @typecast
             if String === value
               ConnectionAdapters::PostgreSQLColumn.string_to_array value, @subtype
             else

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

@@ -169,12 +169,15 @@ def indexes(table_name, name = nil)
         end
 
         # Returns the list of all column definitions for a table.
-        def columns(table_name)
+        def columns(table_name, typecast = true)
           # Limit, precision, and scale are all handled by the superclass.
           column_definitions(table_name).map do |column_name, type, default, notnull, oid, fmod|
             oid = OID::TYPE_MAP.fetch(oid.to_i, fmod.to_i) {
               OID::Identity.new
             }
+            if !typecast && ActiveRecord::ConnectionAdapters::PostgreSQLAdapter::OID::Array === oid && ActiveRecord::ConnectionAdapters::PostgreSQLAdapter::OID::Identity === oid.subtype
+              oid.typecast = false
+            end
             PostgreSQLColumn.new(column_name, default, oid, type, notnull == 'f')
           end
         end

activerecord/lib/active_record/schema_dumper.rb

@@ -94,7 +94,7 @@ def tables(stream)
       end
 
       def table(table, stream)
-        columns = @connection.columns(table)
+        columns = @connection.columns(table, false)
         begin
           tbl = StringIO.new