Sergey Petrunia wrote:
> On 8/29/07, Baron Schwartz <baron@stripped> wrote:
>> Sometimes in EXPLAIN output, I see this in the Extra field:
>> explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 7 and
>> id select_type table type possible_keys key key_len ref rows Extra
>> 1 SIMPLE t1 ref y y 5 const 1 Using where
>> 1 SIMPLE t2 range x x 5 NULL 4 Range checked for each record (index map: 0x1)
>> I know what the rest of it means, but what does 0x1 mean?
> It is a bitmap of indexes which can be used by range/index_merge
> access that is performed for each row combination of the preceding
Thanks Sergey, Chad. Follow-up question: can I assume that in the
output of SHOW CREATE TABLE, 0x1 is the first index, 0x2 is the second,
0x3 is the first and second -- in the order they appear in that output?
If not, how would I be able to tell which indexes the bitmap refers to?