From 60a21d16975de436d57c9e29f237234b71fd5601 Mon Sep 17 00:00:00 2001
From: unknown <ramil/ram@mysql.com/myoffice.izhnet.ru>
Date: Fri, 13 Oct 2006 19:05:54 +0500
Subject: [PATCH] Fix for bug #23254: COMPRESS(NULL) makes all futher
 COMPRESS() calls on same Item return NULL

We don't set null_value to 0 in the Item_func_compress::val_str() for
not-NULL results.


mysql-test/r/func_compress.result:
  Fix for bug #23254: COMPRESS(NULL) makes all futher COMPRESS() calls on same Item return NULL
    - test result.
mysql-test/t/func_compress.test:
  Fix for bug #23254: COMPRESS(NULL) makes all futher COMPRESS() calls on same Item return NULL
    - test case.
sql/item_strfunc.cc:
  Fix for bug #23254: COMPRESS(NULL) makes all futher COMPRESS() calls on same Item return NULL
    - set null_value.
---
 mysql-test/r/func_compress.result | 10 ++++++++++
 mysql-test/t/func_compress.test   | 14 +++++++++++++-
 sql/item_strfunc.cc               |  1 +
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/func_compress.result b/mysql-test/r/func_compress.result
index 8d6fa9927ce..ed8d66e9327 100644
--- a/mysql-test/r/func_compress.result
+++ b/mysql-test/r/func_compress.result
@@ -79,3 +79,13 @@ uncompress(a)	uncompressed_length(a)
 NULL	NULL
 a	1
 drop table t1;
+create table t1(a blob);
+insert into t1 values ('0'), (NULL), ('0');
+select compress(a), compress(a) from t1;
+select compress(a) is null from t1;
+compress(a) is null
+0
+1
+0
+drop table t1;
+End of 4.1 tests
diff --git a/mysql-test/t/func_compress.test b/mysql-test/t/func_compress.test
index 0f3c3cab307..223a5540f38 100644
--- a/mysql-test/t/func_compress.test
+++ b/mysql-test/t/func_compress.test
@@ -54,4 +54,16 @@ insert into t1 values(NULL), (compress('a'));
 select uncompress(a), uncompressed_length(a) from t1;
 drop table t1;
 
-# End of 4.1 tests
+#
+# Bug #23254: problem with compress(NULL)
+#
+
+create table t1(a blob);
+insert into t1 values ('0'), (NULL), ('0');
+--disable_result_log
+select compress(a), compress(a) from t1;
+--enable_result_log
+select compress(a) is null from t1;
+drop table t1;
+
+--echo End of 4.1 tests
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 98888226e58..f7408cb5e9f 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -2838,6 +2838,7 @@ String *Item_func_compress::val_str(String *str)
     null_value= 1;
     return 0;
   }
+  null_value= 0;
   if (res->is_empty()) return res;
 
   /*