diff --git a/innobase/buf/buf0flu.c b/innobase/buf/buf0flu.c
index 6cefdb60956..cad51c224e2 100644
--- a/innobase/buf/buf0flu.c
+++ b/innobase/buf/buf0flu.c
@@ -412,6 +412,9 @@ buf_flush_write_block_low(
 /*======================*/
 	buf_block_t*	block)	/* in: buffer block to write */
 {
+#ifdef UNIV_LOG_DEBUG
+	static ibool univ_log_debug_warned;
+#endif /* UNIV_LOG_DEBUG */
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
 #ifdef UNIV_IBUF_DEBUG
@@ -420,8 +423,13 @@ buf_flush_write_block_low(
 	ut_ad(!ut_dulint_is_zero(block->newest_modification));
 
 #ifdef UNIV_LOG_DEBUG
-	fputs("Warning: cannot force log to disk in the log debug version!\n",
-		stderr);
+	if (!univ_log_debug_warned) {
+		univ_log_debug_warned = TRUE;
+		fputs(
+	"Warning: cannot force log to disk if UNIV_LOG_DEBUG is defined!\n"
+	"Crash recovery will not work!\n",
+			stderr);
+	}
 #else
 	/* Force the log to the disk before writing the modified block */
 	log_write_up_to(block->newest_modification, LOG_WAIT_ALL_GROUPS, TRUE);
diff --git a/innobase/log/log0recv.c b/innobase/log/log0recv.c
index 7e57efcf9e1..e5b0300239a 100644
--- a/innobase/log/log0recv.c
+++ b/innobase/log/log0recv.c
@@ -628,6 +628,9 @@ log_block_checksum_is_ok_or_old_format(
 			format of InnoDB version < 3.23.52 */
 	byte*	block)	/* in: pointer to a log block */
 {
+#ifdef UNIV_LOG_DEBUG
+	return(TRUE);
+#endif /* UNIV_LOG_DEBUG */
 	if (log_block_calc_checksum(block) == log_block_get_checksum(block)) {
 
 		return(TRUE);
diff --git a/innobase/row/row0mysql.c b/innobase/row/row0mysql.c
index 556c80c948d..dfe7f070637 100644
--- a/innobase/row/row0mysql.c
+++ b/innobase/row/row0mysql.c
@@ -2284,7 +2284,6 @@ row_drop_table_for_mysql(
 	"COMMIT WORK;\n"
 	"END;\n";
 
-	ut_ad(trx->mysql_thread_id == os_thread_get_curr_id());
 	ut_a(name != NULL);
 
 	if (srv_created_new_raw) {
diff --git a/myisam/mi_key.c b/myisam/mi_key.c
index d19a3130a86..a9b5a8b279f 100644
--- a/myisam/mi_key.c
+++ b/myisam/mi_key.c
@@ -32,6 +32,9 @@ static int _mi_put_key_in_record(MI_INFO *info,uint keynr,byte *record);
 	** Ret: Length of key
 	*/
 
+#define my_charpos(cs, b, e, num)\
+ (cs)->cset->charpos((cs), (const char*) (b), (const char *)(e), (num))
+
 uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
 		  const byte *record, my_off_t filepos)
 {
@@ -57,6 +60,8 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
   {
     enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type;
     uint length=keyseg->length;
+    uint char_length;
+    CHARSET_INFO *cs;
 
     if (keyseg->null_bit)
     {
@@ -68,6 +73,15 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
       *key++=1;					/* Not NULL */
     }
 
+    char_length= (cs= keyseg->charset) && (cs->mbmaxlen > 1) ?
+                 length / cs->mbmaxlen : 0;
+    
+    if (info->s->keyinfo[keynr].flag & HA_FULLTEXT)
+    {
+      /* Ask Serg to make a better fix */
+      char_length= 0;
+    }
+    
     pos= (byte*) record+keyseg->start;
     if (keyseg->flag & HA_SPACE_PACK)
     {
@@ -83,6 +97,11 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
 	  pos++;
       }
       length=(uint) (end-pos);
+      if (char_length && length > char_length)
+      {
+        char_length= my_charpos(cs, pos, pos+length, char_length);
+        set_if_smaller(length, char_length);
+      }
       store_key_length_inc(key,length);
       memcpy((byte*) key,(byte*) pos,(size_t) length);
       key+=length;
@@ -94,13 +113,26 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
       pos+=2;					/* Skip VARCHAR length */
       set_if_smaller(length,tmp_length);
       store_key_length_inc(key,length);
+      memcpy((byte*) key, pos, length);
+      key+= length;
+      continue;
     }
     else if (keyseg->flag & HA_BLOB_PART)
     {
       uint tmp_length=_mi_calc_blob_length(keyseg->bit_start,pos);
       memcpy_fixed((byte*) &pos,pos+keyseg->bit_start,sizeof(char*));
       set_if_smaller(length,tmp_length);
+#if NOT_YET_BLOB_PART
+      if (char_length && length > char_length)
+      {
+        char_length= my_charpos(cs, pos, pos+length, char_length);
+        set_if_smaller(length, char_length);
+      }
+#endif
       store_key_length_inc(key,length);
+      memcpy((byte*) key, pos, length);
+      key+= length;
+      continue;
     }
     else if (keyseg->flag & HA_SWAP_KEY)
     {						/* Numerical column */
@@ -136,6 +168,13 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
       }
       continue;
     }
+#ifdef NOT_YET_FIXED_LENGTH_KEY
+    if (char_length && length > char_length)
+    {
+      char_length= my_charpos(cs, pos, pos+length, char_length);
+      set_if_smaller(length, char_length);
+    }
+#endif
     memcpy((byte*) key, pos, length);
     key+= length;
   }
diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index b8ca99fe8f1..4d1b5d54bda 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -243,3 +243,36 @@ select 'zвасяz' rlike '[[:<:]]вася[[:>:]]';
 CREATE TABLE t1 (a enum ('Y', 'N') DEFAULT 'N' COLLATE utf8_unicode_ci);
 ALTER TABLE t1 ADD COLUMN b CHAR(20);
 DROP TABLE t1;
+create table t1 (c varchar(30) character set utf8, unique(c(10)));
+insert into t1 values ('1'),('2'),('3'),('x'),('y'),('z');
+insert into t1 values ('aaaaaaaaaa');
+insert into t1 values ('aaaaaaaaaaa');
+ERROR 23000: Duplicate entry 'aaaaaaaaaaa' for key 1
+insert into t1 values ('aaaaaaaaaaaa');
+ERROR 23000: Duplicate entry 'aaaaaaaaaaaa' for key 1
+insert into t1 values (repeat('b',20));
+select c c1 from t1 where c='1';
+c1
+1
+select c c2 from t1 where c='2';
+c2
+2
+select c c3 from t1 where c='3';
+c3
+3
+select c cx from t1 where c='x';
+cx
+x
+select c cy from t1 where c='y';
+cy
+y
+select c cz from t1 where c='z';
+cz
+z
+select c ca10 from t1 where c='aaaaaaaaaa';
+ca10
+aaaaaaaaaa
+select c cb20 from t1 where c=repeat('b',20);
+cb20
+bbbbbbbbbbbbbbbbbbbb
+drop table t1;
diff --git a/mysql-test/r/func_str.result b/mysql-test/r/func_str.result
index e07ee4f0add..345832387bd 100644
--- a/mysql-test/r/func_str.result
+++ b/mysql-test/r/func_str.result
@@ -673,3 +673,6 @@ c1	c2
 2147483647	4294967295
 -2147483648	0
 drop table t1;
+select left(1234, 3) + 0;
+left(1234, 3) + 0
+123
diff --git a/mysql-test/t/ctype_utf8.test b/mysql-test/t/ctype_utf8.test
index 07baee1b3bd..4e130440a24 100644
--- a/mysql-test/t/ctype_utf8.test
+++ b/mysql-test/t/ctype_utf8.test
@@ -165,3 +165,25 @@ select 'zвасяz' rlike '[[:<:]]вася[[:>:]]';
 CREATE TABLE t1 (a enum ('Y', 'N') DEFAULT 'N' COLLATE utf8_unicode_ci);
 ALTER TABLE t1 ADD COLUMN b CHAR(20);
 DROP TABLE t1;
+
+#
+# Bug 4521: unique key prefix interacts poorly with utf8
+# Check keys with prefix compression
+#
+create table t1 (c varchar(30) character set utf8, unique(c(10)));
+insert into t1 values ('1'),('2'),('3'),('x'),('y'),('z');
+insert into t1 values ('aaaaaaaaaa');
+--error 1062
+insert into t1 values ('aaaaaaaaaaa');
+--error 1062
+insert into t1 values ('aaaaaaaaaaaa');
+insert into t1 values (repeat('b',20));
+select c c1 from t1 where c='1';
+select c c2 from t1 where c='2';
+select c c3 from t1 where c='3';
+select c cx from t1 where c='x';
+select c cy from t1 where c='y';
+select c cz from t1 where c='z';
+select c ca10 from t1 where c='aaaaaaaaaa';
+select c cb20 from t1 where c=repeat('b',20);
+drop table t1;
diff --git a/mysql-test/t/func_str.test b/mysql-test/t/func_str.test
index 61d0326f7dd..e7852df40b3 100644
--- a/mysql-test/t/func_str.test
+++ b/mysql-test/t/func_str.test
@@ -402,3 +402,9 @@ insert into t1 values ('-21474836461','-21474836461');
 show warnings;
 select * from t1;
 drop table t1;
+
+#
+# Bug #4878: LEFT() in integer/float context
+#
+
+select left(1234, 3) + 0;
diff --git a/mysql-test/t/grant_cache.test b/mysql-test/t/grant_cache.test
index a82cd732802..e5bde977bb7 100644
--- a/mysql-test/t/grant_cache.test
+++ b/mysql-test/t/grant_cache.test
@@ -67,7 +67,8 @@ show status like "Qcache_queries_in_cache";
 show status like "Qcache_hits";
 show status like "Qcache_not_cached";
 
-connect (unkuser,localhost,,,,$MASTER_MYPORT,master.sock);
+# Don't use '' as user because it will pick Unix login
+connect (unkuser,localhost,unkuser,,,$MASTER_MYPORT,master.sock);
 connection unkuser;
 show grants for current_user();
 
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index d3493e1fad1..995627766c0 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -984,7 +984,10 @@ String *Item_func_left::val_str(String *str)
     return &my_empty_string;
   if (res->length() <= (uint) length)
     return res;
-  str_value.set(*res, 0, res->charpos(length));
+  if (&str_value == res)
+    str_value.length(res->charpos(length));
+  else
+    str_value.set(*res, 0, res->charpos(length));
   return &str_value;
 }
 
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index c81a888d2e9..48a2e1fbc71 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -2535,7 +2535,8 @@ server.");
   if (opt_error_log)
   {
     if (!log_error_file_ptr[0])
-      fn_format(log_error_file, glob_hostname, mysql_data_home, ".err", 0);
+      fn_format(log_error_file, glob_hostname, mysql_data_home, ".err",
+                MY_REPLACE_EXT); /* replace '.<domain>' by '.err', bug#4997 */
     else
       fn_format(log_error_file, log_error_file_ptr, mysql_data_home, ".err",
 		MY_UNPACK_FILENAME | MY_SAFE_PATH);
diff --git a/sql/slave.cc b/sql/slave.cc
index 7e46fb81053..0fe525d766f 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -1236,6 +1236,12 @@ not always make sense; please check the manual before using it).";
   /*
     Check that the master's global character_set_server and ours are the same.
     Not fatal if query fails (old master?).
+    Note that we don't check for equality of global character_set_client and
+    collation_connection (neither do we prevent their setting in
+    set_var.cc). That's because from what I (Guilhem) have tested, the global
+    values of these 2 are never used (new connections don't use them).
+    We don't test equality of global collation_database either as it's is
+    going to be deprecated (made read-only) in 4.1 very soon.
   */
   if (!mysql_real_query(mysql, "SELECT @@GLOBAL.COLLATION_SERVER", 32) &&
       (master_res= mysql_store_result(mysql)))
diff --git a/sql/sql_string.h b/sql/sql_string.h
index 01329c45a98..0179b3ebadc 100644
--- a/sql/sql_string.h
+++ b/sql/sql_string.h
@@ -98,6 +98,7 @@ public:
 
   void set(String &str,uint32 offset,uint32 arg_length)
   {
+    DBUG_ASSERT(&str != this);
     free();
     Ptr=(char*) str.ptr()+offset; str_length=arg_length; alloced=0;
     if (str.Alloced_length)