Merge pull request #543 from larskanis/avoid_set_client_encoding

Don't set the server's client_encoding if it's unnecessary

ext/pg_connection.c

@@ -4171,17 +4171,23 @@ static VALUE
 pgconn_set_default_encoding( VALUE self )
 {
 	PGconn *conn = pg_get_pgconn( self );
-	rb_encoding *enc;
-	const char *encname;
+	rb_encoding *rb_enc;
 
 	rb_check_frozen(self);
-	if (( enc = rb_default_internal_encoding() )) {
-		encname = pg_get_rb_encoding_as_pg_encoding( enc );
-		if ( pgconn_set_client_encoding_async(self, rb_str_new_cstr(encname)) != 0 )
-			rb_warning( "Failed to set the default_internal encoding to %s: '%s'",
-			         encname, PQerrorMessage(conn) );
+	if (( rb_enc = rb_default_internal_encoding() )) {
+		rb_encoding * conn_encoding = pg_conn_enc_get( conn );
+
+		/* Don't set the server encoding, if it's unnecessary.
+		 * This is important for connection proxies, who disallow configuration settings.
+		 */
+		if ( conn_encoding != rb_enc ) {
+			const char *encname = pg_get_rb_encoding_as_pg_encoding( rb_enc );
+			if ( pgconn_set_client_encoding_async(self, rb_str_new_cstr(encname)) != 0 )
+				rb_warning( "Failed to set the default_internal encoding to %s: '%s'",
+								encname, PQerrorMessage(conn) );
+		}
 		pgconn_set_internal_encoding_index( self );
-		return rb_enc_from_encoding( enc );
+		return rb_enc_from_encoding( rb_enc );
 	} else {
 		pgconn_set_internal_encoding_index( self );
 		return Qnil;

spec/pg/connection_spec.rb

@@ -2368,6 +2368,22 @@ def wait_check_socket(conn)
 				end
 			end
 
+			it "doesn't change anything if Encoding.default_internal it set to DB default encoding", :without_transaction do
+				begin
+					prev_encoding = Encoding.default_internal
+					Encoding.default_internal = Encoding::UTF_8
+
+					# PG.connect shouldn't emit a "set client_encoding" for UTF_8, since the server is already on UTF8.
+					conn = PG.connect( @conninfo )
+					expect( conn.internal_encoding ).to eq( Encoding::UTF_8 )
+					res = conn.exec( "SELECT setting, source FROM pg_settings WHERE name='client_encoding'" )
+					expect( res[0].values ).to eq( ['UTF8', 'default'] )
+				ensure
+					conn.finish if conn
+					Encoding.default_internal = prev_encoding
+				end
+			end
+
 			it "allows users of the async interface to set the client_encoding to the default_internal" do
 				begin
 					prev_encoding = Encoding.default_internal