Merge.

mysql-test/include/index_merge1.inc

@@ -334,12 +334,12 @@ update t0 set key2=1, key3=1, key4=1, key5=1,key6=1,key7=1 where key7 < 500;
 --replace_column 9 #
 --replace_result "4,4,4,4,4,4,4" X "4,4,4,4,4,4" X "i6,i7" "i6,i7?" "i6" "i6,i7?"
 explain select max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.key5 + B.key5)
- from t0 as A, t0 as B
+ from t0 as A straight_join t0 as B
  where (A.key1 = 1 and A.key2 = 1 and A.key3 = 1 and A.key4=1 and A.key5=1 and A.key6=1 and A.key7 = 1 or A.key8=1)
   and (B.key1 = 1 and B.key2 = 1 and B.key3 = 1 and B.key4=1 and B.key5=1 and B.key6=1 and B.key7 = 1 or B.key8=1);
 
 select max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.key5 + B.key5)
- from t0 as A, t0 as B
+ from t0 as A straight_join t0 as B
  where (A.key1 = 1 and A.key2 = 1 and A.key3 = 1 and A.key4=1 and A.key5=1 and A.key6=1 and A.key7 = 1 or A.key8=1)
   and (B.key1 = 1 and B.key2 = 1 and B.key3 = 1 and B.key4=1 and B.key5=1 and B.key6=1 and B.key7 = 1 or B.key8=1);
 

mysql-test/include/world_schema.inc

@@ -0,0 +1,25 @@
+CREATE TABLE Country (
+  Code char(3) NOT NULL default '',
+  Name char(52) NOT NULL default '',
+  SurfaceArea float(10,2) NOT NULL default '0.00',
+  Population int(11) NOT NULL default '0',
+  Capital int(11) default NULL,
+  PRIMARY KEY  (Code),
+  UNIQUE INDEX (Name)
+);
+CREATE TABLE City (
+  ID int(11) NOT NULL auto_increment,
+  Name char(35) NOT NULL default '',
+  Country char(3) NOT NULL default '',
+  Population int(11) NOT NULL default '0',
+  PRIMARY KEY  (ID),
+  INDEX (Population),
+  INDEX (Country) 
+);
+CREATE TABLE CountryLanguage (
+  Country char(3) NOT NULL default '',
+  Language char(30) NOT NULL default '',
+  Percentage float(3,1) NOT NULL default '0.0',
+  PRIMARY KEY  (Country, Language),
+  INDEX (Percentage)
+);

mysql-test/r/index_merge_myisam.result

@@ -115,11 +115,11 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 explain select * from t0 where
 (key1 < 3 or key2 < 3) and (key3 < 100);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	range	i1,i2,i3	i3	4	NULL	95	Using where
+1	SIMPLE	t0	index_merge	i1,i2,i3	i1,i2	4,4	NULL	6	Using sort_union(i1,i2); Using where
 explain select * from t0 where
 (key1 < 3 or key2 < 3) and (key3 < 1000);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	ALL	i1,i2,i3	NULL	NULL	NULL	1024	Using where
+1	SIMPLE	t0	index_merge	i1,i2,i3	i1,i2	4,4	NULL	6	Using sort_union(i1,i2); Using where
 explain select * from t0 where
 ((key1 < 4 or key2 < 4) and (key2 <5 or key3 < 4))
 or
@@ -259,7 +259,7 @@ explain
 select * from t0,t1 where (t0.key1=t1.key1) and
 (t0.key1=3 or t0.key2=4) and t1.key1<200;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	ALL	i1,i2	NULL	NULL	NULL	1024	Using where
+1	SIMPLE	t0	index_merge	i1,i2	i1,i2	4,4	NULL	2	Using union(i1,i2); Using where
 1	SIMPLE	t1	ref	i1	i1	4	test.t0.key1	1	
 explain
 select * from t0,t1 where (t0.key1=t1.key1) and
@@ -374,14 +374,14 @@ max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.ke
 alter table t0 add filler1 char(200), add filler2 char(200), add filler3 char(200);
 update t0 set key2=1, key3=1, key4=1, key5=1,key6=1,key7=1 where key7 < 500;
 explain select max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.key5 + B.key5)
-from t0 as A, t0 as B
+from t0 as A straight_join t0 as B
 where (A.key1 = 1 and A.key2 = 1 and A.key3 = 1 and A.key4=1 and A.key5=1 and A.key6=1 and A.key7 = 1 or A.key8=1)
 and (B.key1 = 1 and B.key2 = 1 and B.key3 = 1 and B.key4=1 and B.key5=1 and B.key6=1 and B.key7 = 1 or B.key8=1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	A	index_merge	i1,i2,i3,i4,i5,i6,i7?,i8	i2,i3,i4,i5,i6,i7?,i8	X	NULL	#	Using union(intersect(i2,i3,i4,i5,i6,i7?),i8); Using where
 1	SIMPLE	B	index_merge	i1,i2,i3,i4,i5,i6,i7?,i8	i2,i3,i4,i5,i6,i7?,i8	X	NULL	#	Using union(intersect(i2,i3,i4,i5,i6,i7?),i8); Using where; Using join buffer
 select max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.key5 + B.key5)
-from t0 as A, t0 as B
+from t0 as A straight_join t0 as B
 where (A.key1 = 1 and A.key2 = 1 and A.key3 = 1 and A.key4=1 and A.key5=1 and A.key6=1 and A.key7 = 1 or A.key8=1)
 and (B.key1 = 1 and B.key2 = 1 and B.key3 = 1 and B.key4=1 and B.key5=1 and B.key6=1 and B.key7 = 1 or B.key8=1);
 max(A.key1 + B.key1 + A.key2 + B.key2 + A.key3 + B.key3 + A.key4 + B.key4 + A.key5 + B.key5)

mysql-test/t/range_vs_index_merge_innodb.test

@@ -0,0 +1,7 @@
+--source include/have_innodb.inc
+
+SET SESSION STORAGE_ENGINE='InnoDB';
+
+--source t/range_vs_index_merge.test
+
+SET SESSION STORAGE_ENGINE=DEFAULT;

sql/sql_list.h

@@ -235,6 +235,11 @@ public:
   {
     if (!list->is_empty())
     {
+      if (is_empty())
+      {
+        *this= *list;
+        return;
+      }
       *last= list->first;
       last= list->last;
       elements+= list->elements;