From 5af5bb2da606df8d4f6af7ae8021f3a3ed98ca66 Mon Sep 17 00:00:00 2001
From: "oystein.grovlen@sun.com" <>
Date: Tue, 13 Apr 2010 11:38:28 +0200
Subject: [PATCH] Bug#51980 mysqld service crashes with a simple
 COUNT(DISTINCT) query over a view

Problem: Segmentation fault in add_group_and_distinct_keys() when accessing
field of what is assumed to be an Item_field object.

Cause: In case of views, the item added to list by is_indexed_agg_distinct()
was not of type Item_field, but Item_ref.

Resolution:  Add the real Item_field object, the one referred to by
Item_ref object, to the list, instead.
---
 mysql-test/r/count_distinct.result |  8 ++++++++
 mysql-test/t/count_distinct.test   | 11 +++++++++++
 sql/sql_select.cc                  |  2 +-
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/count_distinct.result b/mysql-test/r/count_distinct.result
index 804bc1f4788..3b65dd0e608 100644
--- a/mysql-test/r/count_distinct.result
+++ b/mysql-test/r/count_distinct.result
@@ -86,3 +86,11 @@ select count(distinct if(f1,3,f2)) from t1;
 count(distinct if(f1,3,f2))
 2
 drop table t1;
+create table t1 (i int);
+insert into t1 values (0), (1);
+create view v1 as select * from t1;
+select count(distinct i) from v1;
+count(distinct i)
+2
+drop table t1;
+drop view v1;
diff --git a/mysql-test/t/count_distinct.test b/mysql-test/t/count_distinct.test
index d0996689aeb..10b4ac6f0e7 100644
--- a/mysql-test/t/count_distinct.test
+++ b/mysql-test/t/count_distinct.test
@@ -96,3 +96,14 @@ insert into t1 values (0,1),(1,2);
 select count(distinct if(f1,3,f2)) from t1;
 drop table t1;
 
+#
+# Bug #51980 "mysqld service crashes with a simple COUNT(DISTINCT) query 
+#             over a view"
+#
+
+create table t1 (i int);
+insert into t1 values (0), (1);
+create view v1 as select * from t1;
+select count(distinct i) from v1;
+drop table t1;
+drop view v1;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 7d379ab34de..62a51a32ca2 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -4157,7 +4157,7 @@ is_indexed_agg_distinct(JOIN *join, List<Item_field> *out_args)
         optimization is applicable 
       */
       if (out_args)
-        out_args->push_back((Item_field *) expr);
+        out_args->push_back((Item_field *) expr->real_item());
       result= true;
     }
   }