A fix (bug #6089: FOUND_ROWS returns wrong values when no table/view is used).

mysql-test/r/ps.result

@@ -135,7 +135,7 @@ FOUND_ROWS()
 1
 execute stmt1;
 FOUND_ROWS()
-0
+1
 deallocate prepare stmt1;
 drop table t1;
 create table t1 

mysql-test/r/select_found.result

@@ -246,3 +246,28 @@ SELECT FOUND_ROWS();
 FOUND_ROWS()
 0
 DROP TABLE t1;
+SELECT 'foo';
+foo
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+SELECT SQL_CALC_FOUND_ROWS 'foo';
+foo
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+SELECT SQL_CALC_FOUND_ROWS 'foo' limit 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+SELECT SQL_CALC_FOUND_ROWS 'foo' UNION SELECT 'bar' LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2

mysql-test/t/select_found.test

@@ -166,3 +166,18 @@ INSERT INTO t1 VALUES (0), (0), (1), (2);
 SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = 0 GROUP BY a HAVING a > 10;
 SELECT FOUND_ROWS();
 DROP TABLE t1;
+
+#
+# Bug #6089: queries which don't use any tables
+#
+
+SELECT 'foo';
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS 'foo';
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS 'foo' limit 0;
+SELECT FOUND_ROWS();
+SELECT FOUND_ROWS();
+
+SELECT SQL_CALC_FOUND_ROWS 'foo' UNION SELECT 'bar' LIMIT 0;
+SELECT FOUND_ROWS();

sql/sql_class.cc

@@ -177,6 +177,7 @@ THD::THD()
   lock=locked_tables=0;
   used_tables=0;
   cuted_fields= sent_row_count= 0L;
+  limit_found_rows= 0;
   statement_id_counter= 0UL;
   // Must be reset to handle error with THD's created for init of mysqld
   lex->current_select= 0;

sql/sql_select.cc

@@ -1067,7 +1067,9 @@ JOIN::exec()
       else
 	error=(int) result->send_eof();
     }
-    thd->limit_found_rows= thd->examined_row_count= 0;
+    /* Single select (without union and limit) always returns 1 row */
+    thd->limit_found_rows= 1;
+    thd->examined_row_count= 0;
     DBUG_VOID_RETURN;
   }
   thd->limit_found_rows= thd->examined_row_count= 0;