On 29 Aug 2007, at 12:26, Baron Schwartz wrote:
> explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 7
> and t1.y+0;
> 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?
Hi Baron. I've never seen this code before, but (grain of salt!)
from my first look it looks like it's a bitmap of which columns are
treated as keys for searching. So, possible values would have been
0x1, 0x2, and (maybe) 0x3. I admit it's not good phrasing. It would
be better to say "index on columns (x)", if we even have the column
name any more at that point.
So, that's my guess. There's some voodoo in there that I don't yet
understand and I may be completely wrong.
Chad Miller, Software Developer chad@stripped
MySQL Inc., www.mysql.com
Orlando, Florida, USA 13-20z, UTC-0400
Office: +1 408 213 6740 sip:6740@stripped
(If it's not cyrptographically signed, it's not from Chad)
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