From e1c614134078b23934555bd76c6cdbd039d8bc28 Mon Sep 17 00:00:00 2001
From: unknown <bar@mysql.com>
Date: Mon, 19 Dec 2005 15:52:10 +0400
Subject: [PATCH]   Bug#15581: COALESCE function truncates mutli-byte TINYTEXT
 values field.cc:   BLOB variations have number-in-bytes limit,   unlike
 CHAR/VARCHAR which have number-of-characters limits.   A tinyblob column can
 store up to 255 bytes.   In the case of basic Latin letters (which use 1 byte
 per character)   we can store up to 255 characters in a tinyblob column.  
 When passing an utf8 tinyblob column as an argument into   a function (e.g.
 COALESCE) we need to reserve 3*255 bytes.   I.e. multiply length in bytes to
 mbcharlen for the character set.   Although in reality a tinyblob column can
 never be 3*255 bytes long,   we need to set max_length to multiply to make
 fix_length_and_dec()   of the function-caller (e.g. COALESCE) calculate the
 correct max_length   for the column being created.

ctype_utf8.result, ctype_utf8.test:
  Adding test case.


mysql-test/t/ctype_utf8.test:
  Adding test case.
mysql-test/r/ctype_utf8.result:
  Adding test case.
sql/field.cc:
  Bug#15581: COALESCE function truncates mutli-byte TINYTEXT values
  BLOB variations have byte limits,
  unlike CHAR/VARCHAR which have number-of-character limits.
  It means tinyblob can store up to 255 bytes.
  All of them can be basic latin letters which use 1 byte
  per character.
  I.e. we can store up to 255 characters in a tinyblob column.
  When passing a tinyblob column as an argument into
  a function (for example COALESCE or CONCAT) we
  need to reserve 3*255 bytes in the case of utf-8.
  I.e. multiply length in bytes to mbcharlen for the
  character set.
---
 mysql-test/r/ctype_utf8.result |  8 ++++++++
 mysql-test/t/ctype_utf8.test   | 10 ++++++++++
 sql/field.cc                   |  6 +++---
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index 03d3ab9f22e..cf9426e6b21 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -1070,3 +1070,11 @@ char(a)
 1
 2
 drop table t1;
+CREATE TABLE t1 (t TINYTEXT CHARACTER SET utf8);
+INSERT INTO t1 VALUES(REPEAT('a', 100));
+CREATE TEMPORARY TABLE t2 SELECT COALESCE(t) AS bug FROM t1;
+SELECT LENGTH(bug) FROM t2;
+LENGTH(bug)
+100
+DROP TABLE t2;
+DROP TABLE t1;
diff --git a/mysql-test/t/ctype_utf8.test b/mysql-test/t/ctype_utf8.test
index 8c0e03c0cd3..01bffe9492e 100644
--- a/mysql-test/t/ctype_utf8.test
+++ b/mysql-test/t/ctype_utf8.test
@@ -882,4 +882,14 @@ set names utf8;
 select distinct char(a) from t1;
 drop table t1;
 
+#
+# Bug#15581: COALESCE function truncates mutli-byte TINYTEXT values
+#
+CREATE TABLE t1 (t TINYTEXT CHARACTER SET utf8);
+INSERT INTO t1 VALUES(REPEAT('a', 100));
+CREATE TEMPORARY TABLE t2 SELECT COALESCE(t) AS bug FROM t1;
+SELECT LENGTH(bug) FROM t2;
+DROP TABLE t2;
+DROP TABLE t1;
+
 # End of 4.1 tests
diff --git a/sql/field.cc b/sql/field.cc
index abb5297f458..b1d9167aee2 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -6949,11 +6949,11 @@ uint32 Field_blob::max_length()
   switch (packlength)
   {
   case 1:
-    return 255;
+    return 255 * field_charset->mbmaxlen;
   case 2:
-    return 65535;
+    return 65535 * field_charset->mbmaxlen;
   case 3:
-    return 16777215;
+    return 16777215 * field_charset->mbmaxlen;
   case 4:
     return (uint32) 4294967295U;
   default: