diff options
Diffstat (limited to 'sql/item.h')
| -rw-r--r-- | sql/item.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/sql/item.h b/sql/item.h index 0cfb0b01fd8..566daa1aaee 100644 --- a/sql/item.h +++ b/sql/item.h @@ -1959,6 +1959,16 @@ public: class Item_in_subselect; + +/* + An object of this class: + - Converts val_XXX() calls to ref->val_XXX_result() calls, like Item_ref. + - Sets owner->was_null=TRUE if it has returned a NULL value from any + val_XXX() function. This allows to inject an Item_ref_null_helper + object into subquery and then check if the subquery has produced a row + with NULL value. +*/ + class Item_ref_null_helper: public Item_ref { protected: |