i was reading file "opt_range.cc", but i'm a bit confused (maybe first impression)
where the per column check occurs?
where the "Impossible WHERE" condiction occurs?
field = ENUM field
WITH enum_values[i], where i start with 0 to ENUM VALUES + 1,
example:
field ENUM ( 1,2,3,4,5,6 ) NOT NULL
max i = 6
field ENUM ( 1,2,3,4,5,6 )
max i = 7
enum_value[0]=1,
enum_value[1]=2,
enum_value[2]=3,
enum_value[3]=4,
enum_value[4]=5,
enum_value[5]=6
enum_value[6]='' -> this allow insert of 10000 value in this field
enum_value[7]=NULL -> if ENUM accept NULL add +1
-------------------------------------
OP could be: =,!=,<>,<,<=,>,>=
(field OP constant_value)
REWRITE TO
(
(field OP constant_value) AND
(
enum_value[0] OP constant_value OR
enum_value[1] OP constant_value OR
...
enum_value[max i - 1] OP constant_value OR
enum_value[max i] OP constant_value
)
)
-------------------------------------
(OP BETWEEN a AND b)
REWRITE TO
(
(field BETWEEN constant_value_1 AND constant_value_2) AND
(
(enum_value[0] BETWEEN constant_value_1 AND constant_value_2) OR
(enum_value[1] BETWEEN constant_value_1 AND constant_value_2) OR
...
(enum_value[ max i - 1 ] BETWEEN constant_value_1 AND constant_value_2) OR
enum_value[ max i ] OP constant_value
)
)
-------------------------------------