From b2d0a33ea04a5eb20124667ea277fe78eb981a90 Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Sat, 6 Apr 2013 00:51:41 -0700
Subject: [PATCH] Fixed bug mdev-4373: Valgrind complained on usage of
 uninitialized memory.

---
 mysql-test/r/selectivity.result        | 17 +++++++++++++++++
 mysql-test/r/selectivity_innodb.result | 17 +++++++++++++++++
 mysql-test/t/selectivity.test          | 23 +++++++++++++++++++++++
 sql/field.cc                           | 12 +++++++-----
 4 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/mysql-test/r/selectivity.result b/mysql-test/r/selectivity.result
index f05b26cc724..e26d2481820 100644
--- a/mysql-test/r/selectivity.result
+++ b/mysql-test/r/selectivity.result
@@ -850,4 +850,21 @@ set optimizer_switch=@save_optimizer_switch;
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 DROP TABLE t1,t2;
 set use_stat_tables=@save_use_stat_tables;
+#
+# Bug mdev-4373: condition on a short varchar column   
+#                with optimizer_use_condition_selectivity=3
+#
+set use_stat_tables=PREFERABLY;
+CREATE TABLE t1 (a varchar(1));
+INSERT INTO t1 VALUES ('x'), ('y');
+ANALYZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+FLUSH TABLES;
+set optimizer_use_condition_selectivity=3;
+SELECT * FROM t1 WHERE a <= 'w';
+a
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+DROP TABLE t1;
+set use_stat_tables=@save_use_stat_tables;
 set use_stat_tables=@save_use_stat_tables;
diff --git a/mysql-test/r/selectivity_innodb.result b/mysql-test/r/selectivity_innodb.result
index 57037574e5d..5f4ddf76383 100644
--- a/mysql-test/r/selectivity_innodb.result
+++ b/mysql-test/r/selectivity_innodb.result
@@ -858,6 +858,23 @@ set optimizer_switch=@save_optimizer_switch;
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 DROP TABLE t1,t2;
 set use_stat_tables=@save_use_stat_tables;
+#
+# Bug mdev-4373: condition on a short varchar column   
+#                with optimizer_use_condition_selectivity=3
+#
+set use_stat_tables=PREFERABLY;
+CREATE TABLE t1 (a varchar(1));
+INSERT INTO t1 VALUES ('x'), ('y');
+ANALYZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+FLUSH TABLES;
+set optimizer_use_condition_selectivity=3;
+SELECT * FROM t1 WHERE a <= 'w';
+a
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+DROP TABLE t1;
+set use_stat_tables=@save_use_stat_tables;
 set use_stat_tables=@save_use_stat_tables;
 set optimizer_switch=@save_optimizer_switch_for_selectivity_test;
 SET SESSION STORAGE_ENGINE=DEFAULT;
diff --git a/mysql-test/t/selectivity.test b/mysql-test/t/selectivity.test
index 095c853d7de..ccd5b09ce68 100644
--- a/mysql-test/t/selectivity.test
+++ b/mysql-test/t/selectivity.test
@@ -444,5 +444,28 @@ DROP TABLE t1,t2;
 
 set use_stat_tables=@save_use_stat_tables;
 
+--echo #
+--echo # Bug mdev-4373: condition on a short varchar column   
+--echo #                with optimizer_use_condition_selectivity=3
+--echo #
+
+set use_stat_tables=PREFERABLY;
+
+CREATE TABLE t1 (a varchar(1));
+INSERT INTO t1 VALUES ('x'), ('y');
+
+ANALYZE TABLE t1;
+FLUSH TABLES;
+
+set optimizer_use_condition_selectivity=3;
+
+SELECT * FROM t1 WHERE a <= 'w';
+
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+
+DROP TABLE t1;
+
+set use_stat_tables=@save_use_stat_tables;
+
 
 set use_stat_tables=@save_use_stat_tables;
diff --git a/sql/field.cc b/sql/field.cc
index 51fa24fc9ad..7eba901d46b 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -6202,14 +6202,16 @@ double Field_str::middle_point_pos(Field *min, Field *max)
   uchar minp_prefix[sizeof(ulonglong)];
   uchar maxp_prefix[sizeof(ulonglong)];
   ulonglong mp, minp, maxp;
+  uint dsz= min(field_length, sizeof(ulonglong) * charset()->mbmaxlen);
+  memset(mp_prefix, 0, sizeof(ulonglong));
+  memset(minp_prefix, 0, sizeof(ulonglong));
+  memset(maxp_prefix, 0, sizeof(ulonglong));
   my_strnxfrm(charset(), mp_prefix, sizeof(mp),
-              ptr + length_size(), sizeof(mp) * charset()->mbmaxlen);
+              ptr + length_size(), dsz);
   my_strnxfrm(charset(), minp_prefix, sizeof(minp),
-              min->ptr + length_size(),
-              sizeof(minp) * charset()->mbmaxlen);
+              min->ptr + length_size(), dsz);
   my_strnxfrm(charset(), maxp_prefix, sizeof(maxp),
-              max->ptr + length_size(),
-              sizeof(maxp) * charset()->mbmaxlen);
+              max->ptr + length_size(), dsz);
   mp= char_prefix_to_ulonglong(mp_prefix);
   minp= char_prefix_to_ulonglong(minp_prefix);
   maxp= char_prefix_to_ulonglong(maxp_prefix);