Assertion `!is_interleave_error' failed on low optimizer_search_depth

As already reported in mysql bug http://bugs.mysql.com/bug.php?id=54429 , using low values for optimizer_search_depth causes an easy crash on multiple-table joins.

The RQG sometimes generates joins involving many tables. In order to restrict the total optimization time per query, and thus run more queries per test run, optimizer_search_depth must be safe to use and not assert.

assertion:
mysqld: sql_select.cc:5498: bool greedy_search(JOIN*, table_map, uint, uint): Assertion `!is_interleave_error' failed.

backtrace:

#8 0x006b0d98 in __assert_fail () from /lib/libc.so.6
#9 0x0831785c in greedy_search (join=0xae688eb0, remaining_tables=55, search_depth=4, prune_level=1) at sql_select.cc:5498
#10 0x08316ebc in choose_plan (join=0xae688eb0, join_tables=55) at sql_select.cc:5120
#11 0x0831205f in make_join_statistics (join=0xae688eb0, tables_arg=0xae631c80, conds=0x0, keyuse_array=0xae68dbec) at sql_select.cc:3216
#12 0x08309e93 in JOIN::optimize (this=0xae688eb0) at sql_select.cc:956
#13 0x0830fa81 in mysql_select (thd=0xb1fda70, rref_pointer_array=0xb1ff50c, tables=0xae631c80, wild_num=0, fields=..., conds=0x0, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=2147764736, result=0xae64b8b0,
    unit=0xb1ff16c, select_lex=0xb1ff408) at sql_select.cc:2607
#14 0x0830800d in handle_select (thd=0xb1fda70, lex=0xb1ff110, result=0xae64b8b0, setup_tables_done_option=0) at sql_select.cc:286
#15 0x082a3400 in execute_sqlcom_select (thd=0xb1fda70, all_tables=0xae631c80) at sql_parse.cc:5070
#16 0x08299e1b in mysql_execute_command (thd=0xb1fda70) at sql_parse.cc:2234
#17 0x082a599e in mysql_parse (thd=0xb1fda70,
    rawbuf=0xae631940 "SELECT table2.f4 FROM t1 AS table1 LEFT JOIN t1 AS table2 LEFT JOIN t2 AS table3 LEFT JOIN t3 AS table4 ON table3 .f1 = table4.f3 ON table2 .f1 LEFT JOIN t4 AS table5 JOIN t5 ON tab"...,
    length=262, found_semicolon=0xae983228) at sql_parse.cc:6077
#18 0x08297904 in dispatch_command (command=COM_QUERY, thd=0xb1fda70,
    packet=0xb217c31 "SELECT table2.f4 FROM t1 AS table1 LEFT JOIN t1 AS table2 LEFT JOIN t2 AS table3 LEFT JOIN t3 AS table4 ON table3 .f1 = table4.f3 ON table2 .f1 LEFT JOIN t4 AS table5 JOIN t5 ON tab"...,
    packet_length=265) at sql_parse.cc:1210
#19 0x08296d6e in do_command (thd=0xb1fda70) at sql_parse.cc:903
#20 0x08293e4a in handle_one_connection (arg=0xb1fda70) at sql_connect.cc:1154
#21 0x00821919 in start_thread () from /lib/libpthread.so.0
#22 0x0076acce in clone () from /lib/libc.so.6

test case:

SET SESSION optimizer_search_depth = 4;

CREATE TABLE t1 (f1 int,f2 int,f3 int,f4 int) ;
INSERT IGNORE INTO t1 VALUES (0,0,2,0),(NULL,0,2,0);

CREATE TABLE t2 (f1 int) ;
CREATE TABLE t3 (f3 int,PRIMARY KEY (f3)) ;
CREATE TABLE t4 (f5 int) ;
CREATE TABLE t5 (f2 int) ;

SELECT alias2.f4 FROM t1 AS alias1
LEFT JOIN t1 AS alias2
        LEFT JOIN t2 AS alias3
        LEFT JOIN t3 AS alias4 ON alias3.f1 = alias4.f3
        ON alias2.f1
LEFT JOIN t4 AS alias5
        JOIN t5 ON alias5.f5
ON alias2.f3 ON alias1.f2 ;