diff options
Diffstat (limited to 'sql/item_cmpfunc.h')
| -rw-r--r-- | sql/item_cmpfunc.h | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h index d1a0c7295db..6ff95dadf15 100644 --- a/sql/item_cmpfunc.h +++ b/sql/item_cmpfunc.h @@ -1614,6 +1614,38 @@ public: Item_bool_func2::get_mm_tree(param, cond_ptr) : Item_func::get_mm_tree(param, cond_ptr); } + Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond) + { + /* + LIKE differs from the regular comparison operator ('=') in the following: + - LIKE never ignores trailing spaces (even for PAD SPACE collations) + Propagation of equal fields with a PAD SPACE collation into LIKE + is not safe. + Example: + WHERE a='a ' AND a LIKE 'a' - returns true for 'a' + cannot be rewritten to: + WHERE a='a ' AND 'a ' LIKE 'a' - returns false for 'a' + Note, binary collations in MySQL/MariaDB, e.g. latin1_bin, + still have the PAD SPACE attribute and ignore trailing spaces! + - LIKE does not take into account contractions, expansions, + and ignorable characters. + Propagation of equal fields with contractions/expansions/ignorables + is also not safe. + + It's safe to propagate my_charset_bin (BINARY/VARBINARY/BLOB) values, + because they do not ignore trailing spaces and have one-to-one mapping + between a string and its weights. + The below condition should be true only for my_charset_bin + (as of version 10.1.7). + */ + uint flags= Item_func_like::compare_collation()->state; + if ((flags & MY_CS_NOPAD) && !(flags & MY_CS_NON1TO1)) + Item_args::propagate_equal_fields(thd, + Context(ANY_SUBST, + compare_collation()), + cond); + return this; + } const char *func_name() const { return "like"; } bool fix_fields(THD *thd, Item **ref); void fix_length_and_dec() |