From aefc060fe59c5b484b5e40a8347575a2471facb4 Mon Sep 17 00:00:00 2001
From: "gkodinov/kgeorge@magare.gmz" <>
Date: Tue, 10 Apr 2007 16:55:48 +0300
Subject: [PATCH] Bug #27659: The optimizer transforms DISTINCT into a GROUP BY
 when possible. It does that by constructing the same structure (a list of
 ORDER instances) the parser makes when parsing GROUP BY. While doing that it
 also eliminates duplicates. But if a duplicate is found it doesn't advance
 the pointer to ref_pointer array, so the next (and subsequent) ORDER
 structures point to the wrong element in the SELECT list. Fixed by advancing
 the pointer in ref_pointer_array even in the case of a duplicate.

---
 mysql-test/r/distinct.result | 14 ++++++++++++++
 mysql-test/t/distinct.test   | 13 +++++++++++++
 sql/sql_select.cc            |  5 ++---
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/mysql-test/r/distinct.result b/mysql-test/r/distinct.result
index 3508a83a810..190e8595126 100644
--- a/mysql-test/r/distinct.result
+++ b/mysql-test/r/distinct.result
@@ -668,3 +668,17 @@ NULL
 3
 4
 DROP TABLE t1;
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES(1,1),(1,2),(1,3);
+SELECT DISTINCT a, b FROM t1;
+a	b
+1	1
+1	2
+1	3
+SELECT DISTINCT a, a, b FROM t1;
+a	a	b
+1	1	1
+1	1	2
+1	1	3
+DROP TABLE t1;
+End of 5.0 tests
diff --git a/mysql-test/t/distinct.test b/mysql-test/t/distinct.test
index 476e4ce7735..7310f98cd16 100644
--- a/mysql-test/t/distinct.test
+++ b/mysql-test/t/distinct.test
@@ -540,3 +540,16 @@ EXPLAIN SELECT a FROM t1 GROUP BY a;
 SELECT a FROM t1 GROUP BY a;
 
 DROP TABLE t1;
+
+#
+#Bug #27659: SELECT DISTINCT returns incorrect result set when field is
+#repeated
+#
+#
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES(1,1),(1,2),(1,3);
+SELECT DISTINCT a, b FROM t1;
+SELECT DISTINCT a, a, b FROM t1;
+DROP TABLE t1;
+
+--echo End of 5.0 tests
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index d65ecb6fa3b..79ae4ade8ab 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -13539,9 +13539,7 @@ create_distinct_group(THD *thd, Item **ref_pointer_array,
       ORDER *ord_iter;
       for (ord_iter= group; ord_iter; ord_iter= ord_iter->next)
         if ((*ord_iter->item)->eq(item, 1))
-          break;
-      if (ord_iter)
-        continue;
+          goto next_item;
       
       ORDER *ord=(ORDER*) thd->calloc(sizeof(ORDER));
       if (!ord)
@@ -13556,6 +13554,7 @@ create_distinct_group(THD *thd, Item **ref_pointer_array,
       *prev=ord;
       prev= &ord->next;
     }
+next_item:
     ref_pointer_array++;
   }
   *prev=0;