Bug#22684 (BENCHMARK, ENCODE, DECODE and FORMAT are not real functions)

Before this change, the functions BENCHMARK, ENCODE, DECODE and FORMAT could
only accept a constant for some parameters.

After this change, this restriction has been removed. An implication is that
these functions can also be used in prepared statements.

The change consist of changing the following classes:
- Item_func_benchmark
- Item_func_encode
- Item_func_decode
- Item_func_format
to:
- only accept Item* in the constructor,
- and evaluate arguments during calls to val_xxx()
which fits the general design of all the other functions.

The 'TODO' items identified in item_create.cc during the work done for
Bug 21114 are addressed by this fix, as a natural consequence of aligning
the design.

In the 'func_str' test, a single very long test line involving an explain
extended select with many functions has been rewritten into multiple
separate tests, to improve maintainability.
The result of explain extended select decode(encode(...)) has changed,
since the encode and decode functions now print all their parameters.

1 files changed, 5 insertions, 13 deletions

diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index 2adccd212b3..423baae371b 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -360,11 +360,9 @@ public:
 
 class Item_func_encode :public Item_str_func
 {
- protected:
-  SQL_CRYPT sql_crypt;
 public:
-  Item_func_encode(Item *a, char *seed):
-    Item_str_func(a),sql_crypt(seed) {}
+  Item_func_encode(Item *a, Item *seed):
+    Item_str_func(a, seed) {}
   String *val_str(String *);
   void fix_length_and_dec();
   const char *func_name() const { return "encode"; }
@@ -374,7 +372,7 @@ public:
 class Item_func_decode :public Item_func_encode
 {
 public:
-  Item_func_decode(Item *a, char *seed): Item_func_encode(a,seed) {}
+  Item_func_decode(Item *a, Item *seed): Item_func_encode(a, seed) {}
   String *val_str(String *);
   const char *func_name() const { return "decode"; }
 };
@@ -507,15 +505,9 @@ class Item_func_format :public Item_str_func
 {
   String tmp_str;
 public:
-  Item_func_format(Item *org,int dec);
+  Item_func_format(Item *org, Item *dec);
   String *val_str(String *);
-  void fix_length_and_dec()
-  {
-    collation.set(default_charset());
-    uint char_length= args[0]->max_length/args[0]->collation.collation->mbmaxlen;
-    max_length= ((char_length + (char_length-args[0]->decimals)/3) *
-                 collation.collation->mbmaxlen);
-  }
+  void fix_length_and_dec();
   const char *func_name() const { return "format"; }
   void print(String *);
 };