Bug#10446 Illegal mix of collations:

item_strfunc.h, item_strfunc.cc, item.cc:
  Try to convert a const item into destination 
  character set. If conversion happens without
  data loss, then cache the converted value
  and return it during val_str().
  Otherwise, if conversion loses data, return
  Illeral mix of collations error, as it happened
  previously.
ctype_recoding.result, ctype_recoding.test:
  Fixing tests accordingly.


sql/item.cc:
  Bug#10446 Illegal mix of collations
  Try to convert a const item into destination 
  character set. If conversion happens without
  data loss, then cache the converted value
  and return it during val_str().
  Otherwise, if conversion loses data, return
  Illeral mix of collations error, as it happened
  previously.
sql/item_strfunc.cc:
  Return cached value when it's possible.
mysql-test/t/ctype_recoding.test:
  Fixing tests accordingly.
mysql-test/r/ctype_recoding.result:
  Fixing tests accordingly.

1 files changed, 2 insertions, 10 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 642a0ccf1b4..5acde7c082d 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -211,16 +211,8 @@ bool Item::eq(const Item *item, bool binary_cmp) const
 
 Item *Item::safe_charset_converter(CHARSET_INFO *tocs)
 {
-  /*
-    Allow conversion from and to "binary".
-    Don't allow automatic conversion to non-Unicode charsets,
-    as it potentially loses data.
-  */
-  if (collation.collation != &my_charset_bin &&
-      tocs != &my_charset_bin &&
-      !(tocs->state & MY_CS_UNICODE))
-    return NULL; // safe conversion is not possible
-  return new Item_func_conv_charset(this, tocs);
+  Item_func_conv_charset *conv= new Item_func_conv_charset(this, tocs, 1);
+  return conv->safe ? conv : NULL;
 }