Fixed bug #29611.

If a primary key is defined over column c of enum type then 
the EXPLAIN command for a look-up query of the form
  SELECT * FROM t WHERE c=0
said that the query was with an impossible where condition though the
query correctly returned non-empty result set when the table indeed 
contained rows with error empty strings for column c. 

This kind of misbehavior was due to a bug in the function 
Field_enum::store(longlong,bool) that erroneously returned 1 if
the the value to be stored was equal to 0. 
Note that the method 
Field_enum::store(const char *from,uint length,CHARSET_INFO *cs)
correctly returned 0 if a value of the error empty string 
was stored. 

1 files changed, 5 insertions, 2 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 993c1fb3c4f..4a1320af48c 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -7640,8 +7640,11 @@ int Field_enum::store(longlong nr, bool unsigned_val)
   if ((ulonglong) nr > typelib->count || nr == 0)
   {
     set_warning(MYSQL_ERROR::WARN_LEVEL_WARN, WARN_DATA_TRUNCATED, 1);
-    nr=0;
-    error=1;
+    if (nr != 0 || table->in_use->count_cuted_fields)
+    {
+      nr= 0;
+      error= 1;
+    }
   }
   store_type((ulonglong) (uint) nr);
   return error;