Fixed LP bug #870046.

This bug is a consequence of the fix in the function add_ref_to_table_cond
for LP bug 826935 that turned out to be not quite correct: it tried to AND
the same generated condition with two different other conditions.
This patch creates a copy of the generated condition if the condition needs
to be ANDed with two different items.

mysql-test/r/myisam_icp.result

@@ -238,4 +238,26 @@ SELECT b FROM t1 WHERE a != 1 AND c IS NULL ORDER BY 1;
 b
 byluovkgwoukfxedyeffsedajyqkyhpaqqpozn
 DROP TABLE t1;
+#
+# Bug#870046: ICP for a GROUP BY query
+#
+CREATE TABLE t1 (a int, b varchar(1), c varchar(1), INDEX idx(b));
+INSERT INTO t1 VALUES (2,'x','x'), (5,'x','y');
+SET SESSION optimizer_switch='index_condition_pushdown=off';
+EXPLAIN
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	idx	idx	4	const	1	Using where; Using temporary; Using filesort
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+a	MIN(c)
+5	y
+SET SESSION optimizer_switch='index_condition_pushdown=on';
+EXPLAIN
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	idx	idx	4	const	1	Using index condition; Using where; Using temporary; Using filesort
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+a	MIN(c)
+5	y
+DROP TABLE t1;
 set optimizer_switch=@myisam_icp_tmp;

mysql-test/t/myisam_icp.test

@@ -209,4 +209,22 @@ INSERT INTO t1 VALUES
 SELECT b FROM t1 WHERE a != 1 AND c IS NULL ORDER BY 1;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#870046: ICP for a GROUP BY query
+--echo #
+
+CREATE TABLE t1 (a int, b varchar(1), c varchar(1), INDEX idx(b));
+INSERT INTO t1 VALUES (2,'x','x'), (5,'x','y');
+
+SET SESSION optimizer_switch='index_condition_pushdown=off';
+EXPLAIN
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+SET SESSION optimizer_switch='index_condition_pushdown=on';
+EXPLAIN
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+SELECT a, MIN(c) FROM t1 WHERE b = 'x' AND c > 'x' GROUP BY a;
+
+DROP TABLE t1;
+
 set optimizer_switch=@myisam_icp_tmp;

sql/sql_select.cc

@@ -19895,6 +19895,7 @@ static bool add_ref_to_table_cond(THD *thd, JOIN_TAB *join_tab)
     DBUG_RETURN(FALSE);
 
   Item_cond_and *cond=new Item_cond_and();
+  Item *cond_copy;
   TABLE *table=join_tab->table;
   int error= 0;
   if (!cond)
@@ -19909,13 +19910,14 @@ static bool add_ref_to_table_cond(THD *thd, JOIN_TAB *join_tab)
   }
   if (thd->is_fatal_error)
     DBUG_RETURN(TRUE);
-
   if (!cond->fixed)
   {
     Item *tmp_item= (Item*) cond;
     cond->fix_fields(thd, &tmp_item);
     DBUG_ASSERT(cond == tmp_item);
   }
+  if (join_tab->select->pre_idx_push_select_cond)
+    cond_copy= cond->copy_andor_structure(thd);
   if (join_tab->select)
   {
     if (join_tab->select->cond)
@@ -19923,7 +19925,7 @@ static bool add_ref_to_table_cond(THD *thd, JOIN_TAB *join_tab)
     join_tab->select->cond= cond;
     if (join_tab->select->pre_idx_push_select_cond)
     {
-      Item *new_cond= and_conds(join_tab->select->pre_idx_push_select_cond, cond);
+      Item *new_cond= and_conds(cond_copy, join_tab->select->pre_idx_push_select_cond);
       if (!new_cond->fixed && new_cond->fix_fields(thd, &new_cond))
         error= 1;
       join_tab->select->pre_idx_push_select_cond= new_cond;