diff --git a/client/mysqldump.c b/client/mysqldump.c
index 3bf9fff1b86..a2a03334ba3 100644
--- a/client/mysqldump.c
+++ b/client/mysqldump.c
@@ -2428,6 +2428,18 @@ static int start_transaction(MYSQL *mysql_con)
     need the REPEATABLE READ level (not anything lower, for example READ
     COMMITTED would give one new consistent read per dumped table).
   */
+  if ((mysql_get_server_version(mysql_con) < 40100) && opt_master_data)
+  {
+    fprintf(stderr, "-- %s: the combination of --single-transaction and "
+            "--master-data requires a MySQL server version of at least 4.1 "
+            "(current server's version is %s). %s\n",
+            ignore_errors ? "Warning" : "Error",
+            mysql_con->server_version ? mysql_con->server_version : "unknown",
+            ignore_errors ? "Continuing due to --force, backup may not be consistent across all tables!" : "Aborting.");
+    if (!ignore_errors)
+      exit(EX_MYSQLERR);
+  }
+
   return (mysql_query_with_error_report(mysql_con, 0,
                                         "SET SESSION TRANSACTION ISOLATION "
                                         "LEVEL REPEATABLE READ") ||
diff --git a/myisam/sort.c b/myisam/sort.c
index b909a16e8e6..728e5b9673e 100644
--- a/myisam/sort.c
+++ b/myisam/sort.c
@@ -559,9 +559,10 @@ int thr_write_keys(MI_SORT_PARAM *sort_param)
       if (!mergebuf)
       {
         length=param->sort_buffer_length;
-        while (length >= MIN_SORT_MEMORY && !mergebuf)
+        while (length >= MIN_SORT_MEMORY)
         {
-          mergebuf=my_malloc(length, MYF(0));
+          if ((mergebuf= my_malloc(length, MYF(0))))
+              break;
           length=length*3/4;
         }
         if (!mergebuf)
@@ -897,6 +898,7 @@ merge_buffers(MI_SORT_PARAM *info, uint keys, IO_CACHE *from_file,
 
   count=error=0;
   maxcount=keys/((uint) (Tb-Fb) +1);
+  DBUG_ASSERT(maxcount > 0);
   LINT_INIT(to_start_filepos);
   if (to_file)
     to_start_filepos=my_b_tell(to_file);
diff --git a/mysql-test/include/ctype_common.inc b/mysql-test/include/ctype_common.inc
index 202c508a9c9..9ee0a40c8ce 100644
--- a/mysql-test/include/ctype_common.inc
+++ b/mysql-test/include/ctype_common.inc
@@ -51,6 +51,15 @@ SELECT c1 as want1result  from t1 where c1 like 'locatio%';
 SELECT c1 as want1result  from t1 where c1 like 'location%';
 DROP TABLE t1;
 
+#
+# Bug #31070: crash during conversion of charsets
+#
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+select a sounds like a from t1;
+drop table t1;
+
 DROP DATABASE d1;
 # Restore settings
 USE test;
diff --git a/mysql-test/r/ctype_big5.result b/mysql-test/r/ctype_big5.result
index 6574908101c..a2651db6308 100644
--- a/mysql-test/r/ctype_big5.result
+++ b/mysql-test/r/ctype_big5.result
@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;
diff --git a/mysql-test/r/ctype_euckr.result b/mysql-test/r/ctype_euckr.result
index 6017bc07763..2d9f8d217e6 100644
--- a/mysql-test/r/ctype_euckr.result
+++ b/mysql-test/r/ctype_euckr.result
@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;
diff --git a/mysql-test/r/ctype_gb2312.result b/mysql-test/r/ctype_gb2312.result
index 314c336bab9..04c318e83a8 100644
--- a/mysql-test/r/ctype_gb2312.result
+++ b/mysql-test/r/ctype_gb2312.result
@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;
diff --git a/mysql-test/r/ctype_gbk.result b/mysql-test/r/ctype_gbk.result
index 241539ecf42..064c0bc2acf 100644
--- a/mysql-test/r/ctype_gbk.result
+++ b/mysql-test/r/ctype_gbk.result
@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;
diff --git a/mysql-test/r/ctype_uca.result b/mysql-test/r/ctype_uca.result
index 91ee427efb4..3d8bd33fb19 100644
--- a/mysql-test/r/ctype_uca.result
+++ b/mysql-test/r/ctype_uca.result
@@ -2371,6 +2371,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;
diff --git a/mysql-test/r/innodb_mysql.result b/mysql-test/r/innodb_mysql.result
index 029f3768f9b..93b93c6253c 100644
--- a/mysql-test/r/innodb_mysql.result
+++ b/mysql-test/r/innodb_mysql.result
@@ -182,4 +182,40 @@ t1.a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 DROP TABLE t1;
+CREATE TABLE t1 (a CHAR(2), KEY (a)) ENGINE = InnoDB DEFAULT CHARSET=UTF8;
+INSERT INTO t1 VALUES ('uk'),('bg');
+SELECT * FROM t1 WHERE a = 'uk';
+a
+uk
+DELETE FROM t1 WHERE a = 'uk';
+SELECT * FROM t1 WHERE a = 'uk';
+a
+UPDATE t1 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t1 WHERE a = 'uk';
+a
+CREATE TABLE t2 (a CHAR(2), KEY (a)) ENGINE = InnoDB;
+INSERT INTO t2 VALUES ('uk'),('bg');
+SELECT * FROM t2 WHERE a = 'uk';
+a
+uk
+DELETE FROM t2 WHERE a = 'uk';
+SELECT * FROM t2 WHERE a = 'uk';
+a
+INSERT INTO t2 VALUES ('uk');
+UPDATE t2 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t2 WHERE a = 'uk';
+a
+CREATE TABLE t3 (a CHAR(2), KEY (a)) ENGINE = MyISAM;
+INSERT INTO t3 VALUES ('uk'),('bg');
+SELECT * FROM t3 WHERE a = 'uk';
+a
+uk
+DELETE FROM t3 WHERE a = 'uk';
+SELECT * FROM t3 WHERE a = 'uk';
+a
+INSERT INTO t3 VALUES ('uk');
+UPDATE t3 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t3 WHERE a = 'uk';
+a
+DROP TABLE t1,t2,t3;
 End of 4.1 tests
diff --git a/mysql-test/r/repair.result b/mysql-test/r/repair.result
index 355a8c25434..fc553c8a698 100644
--- a/mysql-test/r/repair.result
+++ b/mysql-test/r/repair.result
@@ -83,3 +83,30 @@ test.t1	repair	status	OK
 SET myisam_repair_threads=@@global.myisam_repair_threads;
 SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
 DROP TABLE t1;
+CREATE TABLE t1(a CHAR(255), KEY(a));
+SET myisam_sort_buffer_size=4496;
+INSERT INTO t1 VALUES
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0');
+SET myisam_repair_threads=2;
+REPAIR TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	status	OK
+SET myisam_repair_threads=@@global.myisam_repair_threads;
+SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
+DROP TABLE t1;
+End of 4.1 tests
diff --git a/mysql-test/t/innodb_mysql.test b/mysql-test/t/innodb_mysql.test
index b5e7fc6e405..4e20535549a 100644
--- a/mysql-test/t/innodb_mysql.test
+++ b/mysql-test/t/innodb_mysql.test
@@ -216,4 +216,36 @@ t1.a4='UNcT5pIde4I6c2SheTo4gt92OV1jgJCVkXmzyf325R1DwLURkbYHwhydANIZMbKTgdcR5xS';
 
 DROP TABLE t1;
 
+#
+# Bug #28878: InnoDB tables with UTF8 character set and indexes cause wrong result for DML
+#
+
+CREATE TABLE t1 (a CHAR(2), KEY (a)) ENGINE = InnoDB DEFAULT CHARSET=UTF8;
+INSERT INTO t1 VALUES ('uk'),('bg');
+SELECT * FROM t1 WHERE a = 'uk';
+DELETE FROM t1 WHERE a = 'uk';
+SELECT * FROM t1 WHERE a = 'uk';
+UPDATE t1 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t1 WHERE a = 'uk';
+
+CREATE TABLE t2 (a CHAR(2), KEY (a)) ENGINE = InnoDB;
+INSERT INTO t2 VALUES ('uk'),('bg');
+SELECT * FROM t2 WHERE a = 'uk';
+DELETE FROM t2 WHERE a = 'uk';
+SELECT * FROM t2 WHERE a = 'uk';
+INSERT INTO t2 VALUES ('uk');
+UPDATE t2 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t2 WHERE a = 'uk';
+
+CREATE TABLE t3 (a CHAR(2), KEY (a)) ENGINE = MyISAM;
+INSERT INTO t3 VALUES ('uk'),('bg');
+SELECT * FROM t3 WHERE a = 'uk';
+DELETE FROM t3 WHERE a = 'uk';
+SELECT * FROM t3 WHERE a = 'uk';
+INSERT INTO t3 VALUES ('uk');
+UPDATE t3 SET a = 'us' WHERE a = 'uk';
+SELECT * FROM t3 WHERE a = 'uk';
+
+DROP TABLE t1,t2,t3;
+
 --echo End of 4.1 tests
diff --git a/mysql-test/t/repair.test b/mysql-test/t/repair.test
index 35e5e485cb9..1e3facdc3c2 100644
--- a/mysql-test/t/repair.test
+++ b/mysql-test/t/repair.test
@@ -83,4 +83,33 @@ SET myisam_repair_threads=@@global.myisam_repair_threads;
 SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
 DROP TABLE t1;
 
-# End of 4.1 tests
+#
+# BUG#31174 - "Repair" command on MyISAM crashes with small 
+#              myisam_sort_buffer_size
+#
+CREATE TABLE t1(a CHAR(255), KEY(a));
+SET myisam_sort_buffer_size=4496;
+INSERT INTO t1 VALUES
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),('0'),
+('0'),('0'),('0'),('0'),('0'),('0'),('0');
+SET myisam_repair_threads=2;
+REPAIR TABLE t1;
+SET myisam_repair_threads=@@global.myisam_repair_threads;
+SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
+DROP TABLE t1;
+
+--echo End of 4.1 tests
diff --git a/sql/field.cc b/sql/field.cc
index 1b27e12e078..5b43b9b1955 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -5211,7 +5211,8 @@ uint Field_string::get_key_image(char *buff, uint length, CHARSET_INFO *cs,
                           length / field_charset->mbmaxlen);
   memcpy(buff, ptr, bytes);
   if (bytes < length)
-    bzero(buff + bytes, length - bytes);
+    field_charset->cset->fill(field_charset, buff + bytes, length - bytes,
+                              ' ');
   return bytes;
 }
 
diff --git a/strings/ctype-big5.c b/strings/ctype-big5.c
index 89a40b15288..90917229769 100644
--- a/strings/ctype-big5.c
+++ b/strings/ctype-big5.c
@@ -6256,12 +6256,12 @@ my_mb_wc_big5(CHARSET_INFO *cs __attribute__((unused)),
 	      my_wc_t *pwc,const uchar *s,const uchar *e)
 {
 
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;
diff --git a/strings/ctype-cp932.c b/strings/ctype-cp932.c
index e8c62b0315e..3752b2e4118 100644
--- a/strings/ctype-cp932.c
+++ b/strings/ctype-cp932.c
@@ -5352,12 +5352,12 @@ my_wc_mb_cp932(CHARSET_INFO *cs  __attribute__((unused)),
 static int 
 my_mb_wc_cp932(CHARSET_INFO *cs  __attribute__((unused)),
 	      my_wc_t *pwc, const uchar *s, const uchar *e){
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi < 0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;
diff --git a/strings/ctype-euc_kr.c b/strings/ctype-euc_kr.c
index 25ac416ac60..50300f3c140 100644
--- a/strings/ctype-euc_kr.c
+++ b/strings/ctype-euc_kr.c
@@ -8614,12 +8614,12 @@ my_mb_wc_euc_kr(CHARSET_INFO *cs __attribute__((unused)),
 		 my_wc_t *pwc, const uchar *s, const uchar *e)
 {
   
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;
diff --git a/strings/ctype-gb2312.c b/strings/ctype-gb2312.c
index 556f485945b..e81f9d3cf0c 100644
--- a/strings/ctype-gb2312.c
+++ b/strings/ctype-gb2312.c
@@ -5665,12 +5665,10 @@ my_mb_wc_gb2312(CHARSET_INFO *cs  __attribute__((unused)),
 		my_wc_t *pwc, const uchar *s, const uchar *e){
   int hi;
   
-  hi=(int) s[0];
-  
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;
diff --git a/strings/ctype-sjis.c b/strings/ctype-sjis.c
index 38a9c9a6428..92d6b4dc2ae 100644
--- a/strings/ctype-sjis.c
+++ b/strings/ctype-sjis.c
@@ -4512,12 +4512,12 @@ mb:
 static int 
 my_mb_wc_sjis(CHARSET_INFO *cs  __attribute__((unused)),
 	      my_wc_t *pwc, const uchar *s, const uchar *e){
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi < 0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;