Fixed bug mdev-4894.

This a an old legacy performance bug.
When a very selective range scan existed for the second table in a join,
and, at the same time, there was another range condition depending on the
fields of the first table, the optimizer chose a plan with
'Range checked for each record'. This plan was extremely inefficient in
comparison with the regular selective range scan.
As a matter of fact the range scan chosen for each record was the same as
that selective range scan. 

Changed the test case for bug 24776 to preserve the old output for explain.
 

mysql-test/r/range.result

@@ -700,14 +700,14 @@ INSERT INTO t1 VALUES
 'd8c4177d09f8b11f5.52725521');
 EXPLAIN
 SELECT s.oxid FROM t1 v, t1 s 
-WHERE s.oxrootid = 'd8c4177d09f8b11f5.52725521' AND
+WHERE 
 v.oxrootid ='d8c4177d09f8b11f5.52725521' AND
 s.oxleft > v.oxleft AND s.oxleft < v.oxright;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	v	ref	OXLEFT,OXRIGHT,OXROOTID	OXROOTID	34	const	5	Using where
 1	SIMPLE	s	ALL	OXLEFT	NULL	NULL	NULL	6	Range checked for each record (index map: 0x4)
 SELECT s.oxid FROM t1 v, t1 s 
-WHERE s.oxrootid = 'd8c4177d09f8b11f5.52725521' AND
+WHERE
 v.oxrootid ='d8c4177d09f8b11f5.52725521' AND
 s.oxleft > v.oxleft AND s.oxleft < v.oxright;
 oxid
@@ -1884,4 +1884,44 @@ AAA	AAA	AAA
 AAAA	AAAA	AAAA
 AAAAA	AAAAA	AAAAA
 DROP TABLE t1;
+#
+# mdev-4894:  Poor performance with unnecessary 
+# (bug#70021) 'Range checked for each record'
+#
+create table t1( key1 int not null, INDEX i1(key1) );
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8);
+insert into t1 select key1+8 from t1;
+insert into t1 select key1+16 from t1;
+insert into t1 select key1+32 from t1;
+insert into t1 select key1+64 from t1;
+insert into t1 select key1+128 from t1;
+insert into t1 select key1+256 from t1;
+insert into t1 select key1+512 from t1;
+alter table t1 add key2 int not null, add index i2(key2);
+update t1 set key2=key1;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+create table t2 (a int);
+insert into t2 values (1),(2),(3),(4),(5),(6),(7),(8);
+insert into t2 select a+16 from t2;
+insert into t2 select a+32 from t2;
+insert into t2 select a+64 from t2;
+explain
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < 1000;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	64	
+1	SIMPLE	t1	range	i1,i2	i1	4	NULL	78	Using where
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < 1000;
+count(*)
+128
+explain
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < t2.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	64	
+1	SIMPLE	t1	range	i1,i2	i1	4	NULL	78	Using where
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < t2.a;
+count(*)
+126
+drop table t1,t2;
 End of 5.1 tests

mysql-test/t/range.test

@@ -557,12 +557,12 @@ INSERT INTO t1 VALUES
 
 EXPLAIN
 SELECT s.oxid FROM t1 v, t1 s 
-  WHERE s.oxrootid = 'd8c4177d09f8b11f5.52725521' AND
+  WHERE 
         v.oxrootid ='d8c4177d09f8b11f5.52725521' AND
         s.oxleft > v.oxleft AND s.oxleft < v.oxright;
 
 SELECT s.oxid FROM t1 v, t1 s 
-  WHERE s.oxrootid = 'd8c4177d09f8b11f5.52725521' AND
+  WHERE
         v.oxrootid ='d8c4177d09f8b11f5.52725521' AND
         s.oxleft > v.oxleft AND s.oxleft < v.oxright;
 
@@ -1468,4 +1468,38 @@ SELECT * FROM t1 IGNORE INDEX(PRIMARY) WHERE F1 BETWEEN 'A    ' AND
 
 DROP TABLE t1;
 
+--echo #
+--echo # mdev-4894:  Poor performance with unnecessary 
+--echo # (bug#70021) 'Range checked for each record'
+--echo #
+
+create table t1( key1 int not null, INDEX i1(key1) );
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8);
+insert into t1 select key1+8 from t1; 
+insert into t1 select key1+16 from t1; 
+insert into t1 select key1+32 from t1; 
+insert into t1 select key1+64 from t1; 
+insert into t1 select key1+128 from t1; 
+insert into t1 select key1+256 from t1; 
+insert into t1 select key1+512 from t1; 
+
+alter table t1 add key2 int not null, add index i2(key2);
+update t1 set key2=key1;
+analyze table t1;
+
+create table t2 (a int);
+insert into t2 values (1),(2),(3),(4),(5),(6),(7),(8);
+insert into t2 select a+16 from t2;
+insert into t2 select a+32 from t2;
+insert into t2 select a+64 from t2;
+
+explain
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < 1000;
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < 1000;
+explain
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < t2.a;
+select count(*) from t2 left join t1 on (t1.key1 < 3 or t1.key1 > 1020) and t1.key2 < t2.a;
+
+drop table t1,t2;
+
 --echo End of 5.1 tests

sql/sql_select.cc

@@ -6605,19 +6605,18 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
 	  else
 	  {
 	    sel->needed_reg=tab->needed_reg;
-	    sel->quick_keys.clear_all();
 	  }
+	  sel->quick_keys= tab->table->quick_keys;
 	  if (!sel->quick_keys.is_subset(tab->checked_keys) ||
               !sel->needed_reg.is_subset(tab->checked_keys))
 	  {
-	    tab->keys=sel->quick_keys;
-            tab->keys.merge(sel->needed_reg);
 	    tab->use_quick= (!sel->needed_reg.is_clear_all() &&
-			     (select->quick_keys.is_clear_all() ||
-			      (select->quick &&
-			       (select->quick->records >= 100L)))) ?
+			     (sel->quick_keys.is_clear_all() ||
+			      (sel->quick &&
+			       (sel->quick->records >= 100L)))) ?
 	      2 : 1;
 	    sel->read_tables= used_tables & ~current_map;
+            sel->quick_keys.clear_all();
 	  }
 	  if (i != join->const_tables && tab->use_quick != 2)
 	  {					/* Read with cache */