diff options
Diffstat (limited to 'sql/item.cc')
| -rw-r--r-- | sql/item.cc | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/sql/item.cc b/sql/item.cc index 34e5e2da165..de78a2539a7 100644 --- a/sql/item.cc +++ b/sql/item.cc @@ -3789,13 +3789,48 @@ Item_equal *Item_field::find_item_equal(COND_EQUAL *cond_equal) /* + Check whether a field can be substituted by an equal item + + SYNOPSIS + equal_fields_propagator() + arg - *arg != NULL <-> the field is in the context where + substitution for an equal item is valid + + DESCRIPTION + The function checks whether a substitution of the field + occurrence for an equal item is valid. + + NOTES + The following statement is not always true: + x=y => F(x)=F(x/y). + This means substitution of an item for an equal item not always + yields an equavalent condition. + Here's an example: + 'a'='a ' + (LENGTH('a')=1) != (LENGTH('a ')=2) + Such a substitution is surely valid if either the substituted + field is not of a STRING type or if it is an argument of + a comparison predicate. + + RETURN + TRUE substitution is valid + FALSE otherwise +*/ + +bool Item_field::subst_argument_checker(byte **arg) +{ + return (result_type() != STRING_RESULT) || (*arg); +} + + +/* Set a pointer to the multiple equality the field reference belongs to (if any) SYNOPSIS equal_fields_propagator() - arg - reference to list of multiple equalities where - the field (this object) is to be looked for + arg - reference to list of multiple equalities where + the field (this object) is to be looked for DESCRIPTION The function looks for a multiple equality containing the field item @@ -3807,7 +3842,7 @@ Item_equal *Item_field::find_item_equal(COND_EQUAL *cond_equal) NOTES This function is supposed to be called as a callback parameter in calls - of the transform method. + of the compile method. RETURN VALUES pointer to the replacing constant item, if the field item was substituted |