diff options
Diffstat (limited to 'sql/item_cmpfunc.h')
| -rw-r--r-- | sql/item_cmpfunc.h | 39 |
1 files changed, 25 insertions, 14 deletions
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h index 436bbcd259a..cc94a8c08e6 100644 --- a/sql/item_cmpfunc.h +++ b/sql/item_cmpfunc.h @@ -907,18 +907,26 @@ class Item_func_nullif :public Item_func_hybrid_field_type { Arg_comparator cmp; /* - Remember the first argument in case it will be substituted by either of: - - convert_const_compared_to_int_field() + NULLIF(a,b) is a short for: + CASE WHEN a=b THEN NULL ELSE a END + + The left "a" is for comparison purposes. + The right "a" is for return value purposes. + These are two different "a" and they can be replaced to different items. + + The left "a" is in a comparison and can be replaced by: + - Item_func::convert_const_compared_to_int_field() - agg_item_set_converter() in set_cmp_func() - - cache_converted_constant() in set_cmp_func() - The original item will be stored in m_arg0_copy, to return result. - The substituted item will be stored in args[0], for comparison purposes. + - Arg_comparator::cache_converted_constant() in set_cmp_func() + + Both "a"s are subject to equal fields propagation and can be replaced by: + - Item_field::propagate_equal_fields(ANY_SUBST) for the left "a" + - Item_field::propagate_equal_fields(IDENTITY_SUBST) for the right "a" */ - Item *m_args0_copy; public: + // Put "a" to args[0] for comparison and to args[2] for the returned value. Item_func_nullif(THD *thd, Item *a, Item *b): - Item_func_hybrid_field_type(thd, a, b), - m_args0_copy(a) + Item_func_hybrid_field_type(thd, a, b, a) {} bool date_op(MYSQL_TIME *ltime, uint fuzzydate); double real_op(); @@ -926,18 +934,21 @@ public: String *str_op(String *str); my_decimal *decimal_op(my_decimal *); void fix_length_and_dec(); - uint decimal_precision() const { return m_args0_copy->decimal_precision(); } + uint decimal_precision() const { return args[2]->decimal_precision(); } const char *func_name() const { return "nullif"; } void print(String *str, enum_query_type query_type); table_map not_null_tables() const { return 0; } bool is_null(); Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond) { - Item_args::propagate_equal_fields(thd, - Context(ANY_SUBST, - cmp.compare_type(), - cmp.cmp_collation.collation), - cond); + Context cmpctx(ANY_SUBST, cmp.compare_type(), cmp.cmp_collation.collation); + args[0]->propagate_equal_fields_and_change_item_tree(thd, cmpctx, + cond, &args[0]); + args[1]->propagate_equal_fields_and_change_item_tree(thd, cmpctx, + cond, &args[1]); + args[2]->propagate_equal_fields_and_change_item_tree(thd, + Context_identity(), + cond, &args[2]); return this; } }; |