diff -ru mysql-5.0.84_p_orig/innobase/row/row0sel.c mysql-5.0.84/innobase/row/row0sel.c
--- mysql-5.0.84_p_orig/innobase/row/row0sel.c	2009-07-07 21:54:10.000000000 +0900
+++ mysql-5.0.84/innobase/row/row0sel.c	2009-08-28 09:28:56.000000000 +0900
@@ -2988,6 +2988,15 @@
 	return(SEL_FOUND);
 }
 
+/**********************************************************************
+Returns true if the thread is executing a SELECT statement.
+(Prototype for global functions in ha_innodb.cc) */
+ibool
+thd_is_select(
+/*==========*/
+				/* out: true if thd is executing SELECT */
+	const void*	thd);	/* in: thread handle (THD*) */
+
 /************************************************************************
 Searches for rows in the database. This is used in the interface to
 MySQL. This function opens a cursor, and also implements fetch next
@@ -3361,20 +3370,12 @@
 
 	if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
 	    && prebuilt->select_lock_type != LOCK_NONE
-	    && trx->mysql_query_str) {
-
-		/* Scan the MySQL query string; check if SELECT is the first
-	        word there */
-		ibool	success;
-
-		dict_accept(*trx->mysql_query_str, "SELECT", &success);
-
-		if (success) {
+	    && trx->mysql_thd != NULL
+	    && thd_is_select(trx->mysql_thd)) {
 			/* It is a plain locking SELECT and the isolation
 			level is low: do not lock gaps */
 
 			set_also_gap_locks = FALSE;
-		}
 	}
 	
 	/* Note that if the search mode was GE or G, then the cursor
diff -ru mysql-5.0.84_p_orig/sql/ha_innodb.cc mysql-5.0.84/sql/ha_innodb.cc
--- mysql-5.0.84_p_orig/sql/ha_innodb.cc	2009-08-27 16:06:21.000000000 +0900
+++ mysql-5.0.84/sql/ha_innodb.cc	2009-08-28 09:33:38.000000000 +0900
@@ -394,6 +394,18 @@
 	}
 }
 
+/**********************************************************************
+Returns true if the thread is executing a SELECT statement. */
+extern "C"
+ibool
+thd_is_select(
+/*==========*/
+				/* out: true if thd is executing SELECT */
+	const void*	thd)	/* in: thread handle (THD*) */
+{
+	return(((const THD*) thd)->lex->sql_command == SQLCOM_SELECT);
+}
+
 /************************************************************************
 Call this function when mysqld passes control to the client. That is to
 avoid deadlocks on the adaptive hash S-latch possibly held by thd. For more