From 06cf873d8f14b6963e2cccf5ca4a214caeb94977 Mon Sep 17 00:00:00 2001
From: unknown <bar@mysql.com>
Date: Mon, 8 Nov 2004 14:23:14 +0400
Subject: [PATCH] alter_table.result, alter_table.test, field_conv.cc:   Bug
 #6479  ALTER TABLE ... changing charset fails for TEXT columns   Fix: use
 do_conv_blob rather than do_copy_blob   if the column's character sets are
 different.

sql/field_conv.cc:
  Bug #6479  ALTER TABLE ... changing charset fails for TEXT columns
  Fix: use do_conv_blob rather than do_copy_blob
  if the column's character sets are different.
mysql-test/t/alter_table.test:
  Bug #6479  ALTER TABLE ... changing charset fails for TEXT columns
  Fix: use do_conv_blob rather than do_copy_blob
  if the column's character sets are different.
mysql-test/r/alter_table.result:
  Bug #6479  ALTER TABLE ... changing charset fails for TEXT columns
  Fix: use do_conv_blob rather than do_copy_blob
  if the column's character sets are different.
---
 mysql-test/r/alter_table.result | 10 ++++++++++
 mysql-test/t/alter_table.test   | 12 ++++++++++++
 sql/field_conv.cc               |  2 ++
 3 files changed, 24 insertions(+)

diff --git a/mysql-test/r/alter_table.result b/mysql-test/r/alter_table.result
index 89b8bd66848..9e14ca85a29 100644
--- a/mysql-test/r/alter_table.result
+++ b/mysql-test/r/alter_table.result
@@ -483,3 +483,13 @@ ERROR 42000: Incorrect table name 't1\\'
 rename table t1 to `t1\\`;
 ERROR 42000: Incorrect table name 't1\\'
 drop table t1;
+create table t1 (a text) character set koi8r;
+insert into t1 values (_koi8r'ΤΕΣΤ');
+select hex(a) from t1;
+hex(a)
+D4C5D3D4
+alter table t1 convert to character set cp1251;
+select hex(a) from t1;
+hex(a)
+F2E5F1F2
+drop table t1;
diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
index e46027ae8d9..66a4adc90fe 100644
--- a/mysql-test/t/alter_table.test
+++ b/mysql-test/t/alter_table.test
@@ -324,3 +324,15 @@ alter table t1 rename to `t1\\`;
 rename table t1 to `t1\\`;
 drop table t1;
 
+#
+# Bug #6479  ALTER TABLE ... changing charset fails for TEXT columns
+#
+# The column's character set was changed but the actual data was not
+# modified. In other words, the values were reinterpreted
+# as UTF8 instead of being converted.
+create table t1 (a text) character set koi8r;
+insert into t1 values (_koi8r'ΤΕΣΤ');
+select hex(a) from t1;
+alter table t1 convert to character set cp1251;
+select hex(a) from t1;
+drop table t1;
diff --git a/sql/field_conv.cc b/sql/field_conv.cc
index 890687fc925..8a36fcd153c 100644
--- a/sql/field_conv.cc
+++ b/sql/field_conv.cc
@@ -475,6 +475,8 @@ void (*Copy_field::get_copy_func(Field *to,Field *from))(Copy_field*)
   {
     if (!(from->flags & BLOB_FLAG))
       return do_conv_blob;
+    if (from->charset() != to->charset())
+      return do_conv_blob;
     if (from_length != to_length ||
 	to->table->db_low_byte_first != from->table->db_low_byte_first)
     {