PostgreSQL: use standard-conforming strings if possible

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -263,20 +263,12 @@ def supports_primary_key? #:nodoc:
         true
       end
 
-      # Does PostgreSQL support standard conforming strings?
-      def supports_standard_conforming_strings?
-        # Temporarily set the client message level above error to prevent unintentional
-        # error messages in the logs when working on a PostgreSQL database server that
-        # does not support standard conforming strings.
-        client_min_messages_old = client_min_messages
-        self.client_min_messages = 'panic'
-
-        # postgres-pr does not raise an exception when client_min_messages is set higher
-        # than error and "SHOW standard_conforming_strings" fails, but returns an empty
-        # PGresult instead.
-        has_support = query('SHOW standard_conforming_strings')[0][0] rescue false
-        self.client_min_messages = client_min_messages_old
-        has_support
+      # Enable standard-conforming strings if available.
+      def set_standard_conforming_strings
+        old, self.client_min_messages = client_min_messages, 'panic'
+        execute('SET standard_conforming_strings = on') rescue nil
+      ensure
+        self.client_min_messages = old
       end
 
       def supports_insert_with_returning?
@@ -376,9 +368,9 @@ def unescape_bytea(original_value)
       # Quotes PostgreSQL-specific data types for SQL input.
       def quote(value, column = nil) #:nodoc:
         if value.kind_of?(String) && column && column.type == :binary
-          "#{quoted_string_prefix}'#{escape_bytea(value)}'"
+          "'#{escape_bytea(value)}'"
         elsif value.kind_of?(String) && column && column.sql_type == 'xml'
-          "xml E'#{quote_string(value)}'"
+          "xml '#{quote_string(value)}'"
         elsif value.kind_of?(Numeric) && column && column.sql_type == 'money'
           # Not truly string input, so doesn't require (or allow) escape string syntax.
           "'#{value.to_s}'"
@@ -991,22 +983,11 @@ def connect
           # Ignore async_exec and async_query when using postgres-pr.
           @async = @config[:allow_concurrency] && @connection.respond_to?(:async_exec)
 
-          # Use escape string syntax if available. We cannot do this lazily when encountering
-          # the first string, because that could then break any transactions in progress.
-          # See: http://www.postgresql.org/docs/current/static/runtime-config-compatible.html
-          # If PostgreSQL doesn't know the standard_conforming_strings parameter then it doesn't
-          # support escape string syntax. Don't override the inherited quoted_string_prefix.
-          if supports_standard_conforming_strings?
-            self.class.instance_eval do
-              define_method(:quoted_string_prefix) { 'E' }
-            end
-          end
-
           # Money type has a fixed precision of 10 in PostgreSQL 8.2 and below, and as of
           # PostgreSQL 8.3 it has a fixed precision of 19. PostgreSQLColumn.extract_precision
           # should know about this but can't detect it there, so deal with it here.
-          PostgreSQLColumn.money_precision =
-            (postgresql_version >= 80300) ? 19 : 10
+          PostgreSQLColumn.money_precision = (postgresql_version >= 80300) ? 19 : 10
+
           configure_connection
         end
 
@@ -1022,7 +1003,10 @@ def configure_connection
           end
           self.client_min_messages = @config[:min_messages] if @config[:min_messages]
           self.schema_search_path = @config[:schema_search_path] || @config[:schema_order]
-          
+
+          # Use standard-conforming strings if available so we don't have to do the E'...' dance.
+          set_standard_conforming_strings
+
           # If using ActiveRecord's time zone support configure the connection to return
           # TIMESTAMP WITH ZONE types in UTC.
           execute("SET time zone 'UTC'") if ActiveRecord::Base.default_timezone == :utc