Bug#20086: Can't get data from key partitioned tables with VARCHAR key

The problem appeared because the same values produced different hash
during INSERT and SELECT for VARCHAR data type.
Fix:
VARCHAR required special treatment to avoid hashing of length bytes
(leftmost one or two bytes) as well as trailing bytes beyond real length,
which could contain garbage. Fix is done by introducing hash() - new method
in the Field class.

mysql-test/r/partition_innodb.result

@@ -92,3 +92,18 @@ DROP TABLE IF EXISTS t1;
 DROP TABLE IF EXISTS t0_aux;
 DROP TABLE IF EXISTS t0_definition;
 DROP TABLE IF EXISTS t0_template;
+create table t1 (id varchar(64) primary key) engine=innodb
+partition by key(id) partitions 5;
+insert into t1 values ('a');
+insert into t1 values ('aa');
+insert into t1 values ('aaa');
+select * from t1 where id = 'a';
+id
+a
+select * from t1 where id = 'aa';
+id
+aa
+select * from t1 where id = 'aaa';
+id
+aaa
+drop table t1;

mysql-test/r/partition_pruning.result

@@ -31,7 +31,7 @@ id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	p0,p1	ALL	NULL	NULL	NULL	NULL	3	Using where
 explain partitions select * from t2 where a=1 and b=1;
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	p0	ALL	NULL	NULL	NULL	NULL	3	Using where
+1	SIMPLE	t2	p0	ALL	NULL	NULL	NULL	NULL	2	Using where
 create table t3 (
 a int
 )

mysql-test/t/partition_innodb.test

@@ -66,3 +66,15 @@ DROP TABLE IF EXISTS t0_definition;
 DROP TABLE IF EXISTS t0_template;
 --enable_warnings
 
+#
+# Bug#20086: Can't get data from key partitioned tables with VARCHAR key
+#
+create table t1 (id varchar(64) primary key) engine=innodb
+partition by key(id) partitions 5;
+insert into t1 values ('a');
+insert into t1 values ('aa');
+insert into t1 values ('aaa');
+select * from t1 where id = 'a';
+select * from t1 where id = 'aa';
+select * from t1 where id = 'aaa';
+drop table t1;

sql/field.cc

@@ -1243,6 +1243,21 @@ uint Field::offset()
 }
 
 
+void Field::hash(ulong *nr, ulong *nr2)
+{
+  if (is_null())
+  {
+    *nr^= (*nr << 1) | 1;
+  }
+  else
+  {
+    uint len= pack_length();
+    CHARSET_INFO *cs= charset();
+    cs->coll->hash_sort(cs, (uchar*) ptr, len, nr, nr2);
+  }
+}
+
+
 void Field::copy_from_tmp(int row_offset)
 {
   memcpy(ptr,ptr+row_offset,pack_length());
@@ -6923,6 +6938,21 @@ uint Field_varstring::is_equal(create_field *new_field)
 }
 
 
+void Field_varstring::hash(ulong *nr, ulong *nr2)
+{
+  if (is_null())
+  {
+    *nr^= (*nr << 1) | 1;
+  }
+  else
+  {
+    uint len=  length_bytes == 1 ? (uint) (uchar) *ptr : uint2korr(ptr);
+    CHARSET_INFO *cs= charset();
+    cs->coll->hash_sort(cs, (uchar*) ptr + length_bytes, len, nr, nr2);
+  }
+}
+
+
 /****************************************************************************
 ** blob type
 ** A blob is saved as a length and a pointer. The length is stored in the

sql/field.h

@@ -351,6 +351,8 @@ class Field
     return field_length / charset()->mbmaxlen;
   }
 
+  /* Hash value */
+  virtual void hash(ulong *nr, ulong *nr2);
   friend bool reopen_table(THD *,struct st_table *,bool);
   friend int cre_myisam(my_string name, register TABLE *form, uint options,
 			ulonglong auto_increment_value);
@@ -1120,6 +1122,7 @@ class Field_varstring :public Field_longstr {
                        char *new_ptr, uchar *new_null_ptr,
                        uint new_null_bit);
   uint is_equal(create_field *new_field);
+  void hash(ulong *nr, ulong *nr2);
 };
 
 

sql/key.cc

@@ -210,9 +210,13 @@ void key_restore(byte *to_record, byte *from_key, KEY *key_info,
     }
     else if (key_part->key_part_flag & HA_VAR_LENGTH_PART)
     {
+      my_bitmap_map *old_map;
       key_length-= HA_KEY_BLOB_LENGTH;
       length= min(key_length, key_part->length);
+      old_map= dbug_tmp_use_all_columns(key_part->field->table,
+                                        key_part->field->table->write_set);
       key_part->field->set_key_image((char *) from_key, length);
+      dbug_tmp_restore_column_map(key_part->field->table->write_set, old_map);
       from_key+= HA_KEY_BLOB_LENGTH;
     }
     else

sql/sql_partition.cc

@@ -2103,26 +2103,15 @@ static inline longlong part_val_int(Item *item_expr)
 
 static uint32 calculate_key_value(Field **field_array)
 {
-  uint32 hashnr= 0;
+  ulong nr1= 1;
   ulong nr2= 4;
 
   do
   {
     Field *field= *field_array;
-    if (field->is_null())
-    {
-      hashnr^= (hashnr << 1) | 1;
-    }
-    else
-    {
-      uint len= field->pack_length();
-      ulong nr1= 1;
-      CHARSET_INFO *cs= field->charset();
-      cs->coll->hash_sort(cs, (uchar*)field->ptr, len, &nr1, &nr2);
-      hashnr^= (uint32)nr1;
-    }
+    field->hash(&nr1, &nr2);
   } while (*(++field_array));
-  return hashnr;
+  return (uint32) nr1;
 }