Explainの入口 - mir the developer

JOIN:execからselect_describe。
#0  select_describe (join=0xff90870, need_tmp_table=false, need_order=false, distinct=false, message=0x0) at sql_select.cc:14969
#1  0x0000000000637881 in JOIN::exec (this=0xff90870) at sql_select.cc:1645
#2  0x000000000063518e in mysql_select (thd=0xfe71d90, rref_pointer_array=0xfe737d0, tables=0xfeb0310, wild_num=1, fields=@0xfe736b0, conds=0xfeb0750, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, 
    select_options=2156153348, result=0xfeb0960, unit=0xfe731f8, select_lex=0xfe735a8) at sql_select.cc:2240
#3  0x00000000006356b7 in mysql_explain_union (thd=0xfe71d90, unit=0xfe731f8, result=0xfeb0960) at sql_select.cc:15367
#4  0x00000000005d03b0 in mysql_execute_command (thd=0xfe71d90) at sql_parse.cc:2651
#5  0x00000000005d7bc7 in mysql_parse (thd=0xfe71d90, inBuf=0xfeb0160 "explain select * from t3 where c1>1", length=35) at sql_parse.cc:5986
#6  0x00000000005da14f in dispatch_command (command=COM_QUERY, thd=0xfe71d90, packet=0xfea8131 "", packet_length=36) at sql_parse.cc:1807
#7  0x00000000005db7c9 in do_command (thd=0xfe71d90) at sql_parse.cc:1586
#8  0x00000000005dca4c in handle_one_connection (arg=0xfe71d90) at sql_parse.cc:1200
#9  0x0000003ca5a061b5 in start_thread () from /lib64/libpthread.so.0
#10 0x0000003ca4ecd36d in clone () from /lib64/libc.so.6
#11 0x0000000000000000 in ?? ()