From 2e8542f4620fd64e65eb6e41122bbe166c242a01 Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Wed, 20 Jul 2011 21:55:55 -0700
Subject: [PATCH] Fixed LP bug #791761. An aggregating query over an empty set
 of a join of two tables with a rejecting HAVING clause erroneously could
 return a row. It could happen in the cases when the optimizer made a
 conclusion that the aggregating set was empty. Wrong results were produced
 because the server missed initial setting for aggregation functions in the
 mentioned cases.

---
 mysql-test/r/having.result | 24 ++++++++++++++++++++++++
 mysql-test/t/having.test   | 25 +++++++++++++++++++++++++
 sql/item.h                 |  1 +
 sql/item_sum.h             |  1 +
 sql/sql_select.cc          |  4 +++-
 5 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/having.result b/mysql-test/r/having.result
index fc2df2b7fc2..e631c7dbe5a 100644
--- a/mysql-test/r/having.result
+++ b/mysql-test/r/having.result
@@ -570,3 +570,27 @@ ORDER BY t1.f1;
 f1
 DROP TABLE t1,t2;
 End of 5.1 tests
+#
+# LP bug #791761: MAX over an empty join + HAVING
+#
+CREATE TABLE t1 (a int, b int , KEY (b)) ;
+INSERT INTO t1 VALUES (3,1);
+CREATE TABLE t2 (a int NOT NULL ) ;
+INSERT INTO t2 VALUES (29);
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a > 0 HAVING MAX(t1.b) <> 6;
+MAX(t1.b)
+1
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a > 0 HAVING MAX(t1.b) IS NULL;
+MAX(t1.b)
+EXPLAIN
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a < 0 HAVING MAX(t1.b) <> 6;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a < 0 HAVING MAX(t1.b) <> 6;
+MAX(t1.b)
+CREATE TABLE t3 ( f3 int) ;
+INSERT INTO t3 VALUES (NULL);
+SELECT MAX(t1.b) AS f FROM t1 JOIN t2 ON t2.a != 0
+WHERE (SELECT f3 FROM t3) <> 0 HAVING f <> 6 ;
+f
+DROP TABLE t1,t2,t3;
diff --git a/mysql-test/t/having.test b/mysql-test/t/having.test
index 2ed8b40b858..01342fdf5fa 100644
--- a/mysql-test/t/having.test
+++ b/mysql-test/t/having.test
@@ -591,3 +591,28 @@ DROP TABLE t1,t2;
 
 
 --echo End of 5.1 tests
+
+--echo #
+--echo # LP bug #791761: MAX over an empty join + HAVING
+--echo #
+
+CREATE TABLE t1 (a int, b int , KEY (b)) ;
+INSERT INTO t1 VALUES (3,1);
+
+CREATE TABLE t2 (a int NOT NULL ) ;
+INSERT INTO t2 VALUES (29);
+
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a > 0 HAVING MAX(t1.b) <> 6;
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a > 0 HAVING MAX(t1.b) IS NULL;
+
+EXPLAIN
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a < 0 HAVING MAX(t1.b) <> 6;
+SELECT MAX(t1.b)  FROM t1,t2 WHERE t2.a < 0 HAVING MAX(t1.b) <> 6;
+
+CREATE TABLE t3 ( f3 int) ;
+INSERT INTO t3 VALUES (NULL);
+
+SELECT MAX(t1.b) AS f FROM t1 JOIN t2 ON t2.a != 0
+  WHERE (SELECT f3 FROM t3) <> 0 HAVING f <> 6 ;
+
+DROP TABLE t1,t2,t3;
diff --git a/sql/item.h b/sql/item.h
index f2e7a2587da..8a453f31c7e 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1020,6 +1020,7 @@ public:
   virtual bool set_fake_select_as_master_processor(uchar *arg) { return 0; }
   virtual bool view_used_tables_processor(uchar *arg) { return 0; }
   virtual bool eval_not_null_tables(uchar *opt_arg) { return 0; }
+  virtual bool clear_sum_processor(uchar *opt_arg) { return 0; }
 
   /* To call bool function for all arguments */
   struct bool_func_call_args
diff --git a/sql/item_sum.h b/sql/item_sum.h
index 7b6bdbabf7f..0d557a030d8 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -388,6 +388,7 @@ public:
   {
     return trace_unsupported_by_check_vcol_func_processor(func_name()); 
   }
+  bool clear_sum_processor(uchar *arg) { clear(); return 0; }
 };
 
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index c4f03cf2c4f..eacebcb498a 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -10146,7 +10146,9 @@ return_zero_rows(JOIN *join, select_result *result, List<TABLE_LIST> &tables,
     TABLE_LIST *table;
     while ((table= ti++))
       mark_as_null_row(table->table);		// All fields are NULL
-    if (having && having->val_int() == 0)
+    if (having &&
+        !having->walk(&Item::clear_sum_processor, FALSE, NULL) &&
+        having->val_int() == 0)
       send_row=0;
   }
   if (!(result->send_fields(fields,