1 files changed, 31 insertions, 5 deletions
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index 5155ced0e2..533e6953a4 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -1,8 +1,13 @@
+# frozen_string_literal: true
+
+require "tempfile"
+
 module ActiveRecord
   module Tasks # :nodoc:
     class PostgreSQLDatabaseTasks # :nodoc:
       DEFAULT_ENCODING = ENV["CHARSET"] || "utf8"
       ON_ERROR_STOP_1 = "ON_ERROR_STOP=1".freeze
+      SQL_COMMENT_BEGIN = "--".freeze
 
       delegate :connection, :establish_connection, :clear_active_connections!,
         to: ActiveRecord::Base
@@ -17,7 +22,7 @@ module ActiveRecord
           configuration.merge("encoding" => encoding)
         establish_connection configuration
       rescue ActiveRecord::StatementInvalid => error
-        if /database .* already exists/.match?(error.message)
+        if error.cause.is_a?(PG::DuplicateDatabase)
           raise DatabaseAlreadyExists
         else
           raise
@@ -63,8 +68,15 @@ module ActiveRecord
             "--schema=#{part.strip}"
           end
         end
+
+        ignore_tables = ActiveRecord::SchemaDumper.ignore_tables
+        if ignore_tables.any?
+          args += ignore_tables.flat_map { |table| ["-T", table] }
+        end
+
         args << configuration["database"]
         run_cmd("pg_dump", args, "dumping")
+        remove_sql_header_comments(filename)
         File.open(filename, "a") { |f| f << "SET search_path TO #{connection.schema_search_path};\n\n" }
       end
 
@@ -78,9 +90,7 @@ module ActiveRecord
 
       private
 
-        def configuration
-          @configuration
-        end
+        attr_reader :configuration
 
         def encoding
           configuration["encoding"] || DEFAULT_ENCODING
@@ -105,11 +115,27 @@ module ActiveRecord
         end
 
         def run_cmd_error(cmd, args, action)
-          msg = "failed to execute:\n"
+          msg = "failed to execute:\n".dup
           msg << "#{cmd} #{args.join(' ')}\n\n"
           msg << "Please check the output above for any errors and make sure that `#{cmd}` is installed in your PATH and has proper permissions.\n\n"
           msg
         end
+
+        def remove_sql_header_comments(filename)
+          removing_comments = true
+          tempfile = Tempfile.open("uncommented_structure.sql")
+          begin
+            File.foreach(filename) do |line|
+              unless removing_comments && (line.start_with?(SQL_COMMENT_BEGIN) || line.blank?)
+                tempfile << line
+                removing_comments = false
+              end
+            end
+          ensure
+            tempfile.close
+          end
+          FileUtils.cp(tempfile.path, filename)
+        end
     end
   end
 end