diff options
Diffstat (limited to 'sql/item.h')
| -rw-r--r-- | sql/item.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/sql/item.h b/sql/item.h index f66892a76cc..4bee370642e 100644 --- a/sql/item.h +++ b/sql/item.h @@ -556,10 +556,17 @@ public: Field *make_string_field(TABLE *table); virtual bool fix_fields(THD *, Item **); /* - should be used in case where we are sure that we do not need + This method should be used in case where we are sure that we do not need complete fix_fields() procedure. - */ - inline void quick_fix_field() { fixed= 1; } + Usually this method is used by the optimizer when it has to create a new + item out of other already fixed items. For example, if the optimizer has + to create a new Item_func for an inferred equality whose left and right + parts are already fixed items. In some cases the optimizer cannot use + directly fixed items as the arguments of the created functional item, + but rather uses intermediate type conversion items. Then the method is + supposed to be applied recursively. + */ + virtual inline void quick_fix_field() { fixed= 1; } /* Function returns 1 on overflow and -1 on fatal errors */ int save_in_field_no_warnings(Field *field, bool no_conversions); virtual int save_in_field(Field *field, bool no_conversions); |