Fix for bug #26447: "ALTER TABLE .. ORDER" does not work with InnoDB

and auto_increment keys

Problems: 
  1. ALTER TABLE ... ORDER BY... doesn't make sence if there's a 
     user-defined clustered index in the table.
  2. using a secondary index is slower than using a clustered one 
     for a table scan.

Fixes:
  1. raise a warning.
  2. use the clustered index.

mysql-test/include/mix1.inc

@@ -1189,4 +1189,12 @@ if ($test_foreign_keys)
   DROP TABLE t1;
 }
 
+#
+# Bug #26447: "ALTER TABLE .. ORDER" does not work with InnoDB and 
+#             auto_increment keys
+#
+create table t1 (a int auto_increment primary key) engine=innodb;
+alter table t1 order by a;
+drop table t1;
+
 --echo End of 5.1 tests

mysql-test/r/innodb.result

@@ -962,7 +962,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	NULL	b	4	NULL	#	Using index
 explain select a,b from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	NULL	b	4	NULL	#	Using index
+1	SIMPLE	t1	index	NULL	PRIMARY	4	NULL	#	
 explain select a,b,c from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	#	
@@ -1177,14 +1177,14 @@ UPDATE t1 set a=a+100 where b between 2 and 3 and a < 1000;
 SELECT * from t1;
 a	b
 1	1
-102	2
-103	3
 4	4
 5	5
 6	6
 7	7
 8	8
 9	9
+102	2
+103	3
 drop table t1;
 CREATE TABLE t1 (a int not null primary key, b int not null, key (b)) engine=innodb;
 CREATE TABLE t2 (a int not null primary key, b int not null, key (b)) engine=innodb;
@@ -1208,7 +1208,6 @@ a	b
 update t1,t2 set t1.a=t1.a+100 where t1.a=101;
 select * from t1;
 a	b
-201	1
 102	2
 103	3
 104	4
@@ -1220,10 +1219,11 @@ a	b
 110	10
 111	11
 112	12
+201	1
 update t1,t2 set t1.b=t1.b+10 where t1.b=2;
 select * from t1;
 a	b
-201	1
+102	12
 103	3
 104	4
 105	5
@@ -1233,34 +1233,34 @@ a	b
 109	9
 110	10
 111	11
-102	12
 112	12
+201	1
 update t1,t2 set t1.b=t1.b+2,t2.b=t1.b+10 where t1.b between 3 and 5 and t1.a=t2.a+100;
 select * from t1;
 a	b
-201	1
+102	12
 103	5
 104	6
-106	6
 105	7
+106	6
 107	7
 108	8
 109	9
 110	10
 111	11
-102	12
 112	12
+201	1
 select * from t2;
 a	b
 1	1
 2	2
+3	13
+4	14
+5	15
 6	6
 7	7
 8	8
 9	9
-3	13
-4	14
-5	15
 drop table t1,t2;
 CREATE TABLE t2 (   NEXT_T         BIGINT NOT NULL PRIMARY KEY) ENGINE=MyISAM;
 CREATE TABLE t1 (  B_ID           INTEGER NOT NULL PRIMARY KEY) ENGINE=InnoDB;
@@ -1311,11 +1311,11 @@ insert into t1 (id) values (null),(null),(null),(null),(null);
 update t1 set fk=69 where fk is null order by id limit 1;
 SELECT * from t1;
 id	fk
+1	69
 2	NULL
 3	NULL
 4	NULL
 5	NULL
-1	69
 drop table t1;
 create table t1 (a int not null, b int not null, key (a));
 insert into t1 values (1,1),(1,2),(1,3),(3,1),(3,2),(3,3),(3,1),(3,2),(3,3),(2,1),(2,2),(2,3);
@@ -2444,8 +2444,8 @@ insert into t1 (b) values (1);
 replace into t1 (b) values (2), (1), (3);
 select * from t1;
 a	b
-3	1
 2	2
+3	1
 4	3
 truncate table t1;
 insert into t1 (b) values (1);
@@ -2454,8 +2454,8 @@ replace into t1 (b) values (1);
 replace into t1 (b) values (3);
 select * from t1;
 a	b
-3	1
 2	2
+3	1
 4	3
 drop table t1;
 create table t1 (rowid int not null auto_increment, val int not null,primary

mysql-test/r/innodb_mysql.result

@@ -352,13 +352,13 @@ EXPLAIN
 SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id
 WHERE t1.name LIKE 'A%';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	PRIMARY,name	name	23	NULL	3	Using where; Using index
+1	SIMPLE	t1	index	PRIMARY,name	PRIMARY	4	NULL	3	Using where
 1	SIMPLE	t2	ref	fkey	fkey	5	test.t1.id	1	Using where; Using index
 EXPLAIN
 SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id
 WHERE t1.name LIKE 'A%' OR FALSE;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	index	NULL	fkey	5	NULL	5	Using index
+1	SIMPLE	t2	index	NULL	PRIMARY	4	NULL	5	
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.fkey	1	Using where
 DROP TABLE t1,t2;
 CREATE TABLE t1 (
@@ -1260,11 +1260,11 @@ select_type	SIMPLE
 table	t1
 type	index
 possible_keys	NULL
-key	b
-key_len	5
+key	PRIMARY
+key_len	4
 ref	NULL
 rows	3
-Extra	Using index; Using filesort
+Extra	Using filesort
 SELECT * FROM t1 ORDER BY b ASC, a DESC;
 a	b
 1	1
@@ -1276,11 +1276,11 @@ select_type	SIMPLE
 table	t1
 type	index
 possible_keys	NULL
-key	b
-key_len	5
+key	PRIMARY
+key_len	4
 ref	NULL
 rows	3
-Extra	Using index; Using filesort
+Extra	Using filesort
 SELECT * FROM t1 ORDER BY b DESC, a ASC;
 a	b
 2	2
@@ -1470,4 +1470,9 @@ t2	CREATE TABLE `t2` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE t2;
 DROP TABLE t1;
+create table t1 (a int auto_increment primary key) engine=innodb;
+alter table t1 order by a;
+Warnings:
+Warning	1105	ORDER BY ignored as there is a user-defined clustered index in the table 't1'
+drop table t1;
 End of 5.1 tests

mysql-test/r/join_outer_innodb.result

@@ -8,12 +8,12 @@ EXPLAIN
 SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id 
 WHERE t1.name LIKE 'A%';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	PRIMARY,name	name	23	NULL	3	Using where; Using index
+1	SIMPLE	t1	index	PRIMARY,name	PRIMARY	4	NULL	3	Using where
 1	SIMPLE	t2	ref	fkey	fkey	5	test.t1.id	1	Using where; Using index
 EXPLAIN
 SELECT COUNT(*) FROM t2 LEFT JOIN t1 ON t2.fkey = t1.id 
 WHERE t1.name LIKE 'A%' OR FALSE;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	index	NULL	fkey	5	NULL	5	Using index
+1	SIMPLE	t2	index	NULL	PRIMARY	4	NULL	5	
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.fkey	1	Using where
 DROP TABLE t1,t2;

sql/sql_select.cc

@@ -6436,7 +6436,15 @@ make_join_readinfo(JOIN *join, ulonglong options)
 	  else if (!table->covering_keys.is_clear_all() &&
 		   !(tab->select && tab->select->quick))
 	  {					// Only read index tree
-	    tab->index=find_shortest_key(table, & table->covering_keys);
+	    /*
+	      See bug #26447: "Using the clustered index for a table scan
+	      is always faster than using a secondary index".
+	    */
+            if (table->s->primary_key != MAX_KEY &&
+                table->file->primary_key_is_clustered())
+              tab->index= table->s->primary_key;
+            else
+              tab->index=find_shortest_key(table, & table->covering_keys);
 	    tab->read_first_record= join_read_first;
 	    tab->type=JT_NEXT;		// Read with index_first / index_next
 	  }

sql/sql_table.cc

@@ -6813,23 +6813,35 @@ copy_data_between_tables(TABLE *from,TABLE *to,
 
   if (order)
   {
-    from->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),
-					      MYF(MY_FAE | MY_ZEROFILL));
-    bzero((char*) &tables,sizeof(tables));
-    tables.table= from;
-    tables.alias= tables.table_name= from->s->table_name.str;
-    tables.db=    from->s->db.str;
-    error=1;
+    if (to->s->primary_key != MAX_KEY && to->file->primary_key_is_clustered())
+    {
+      char warn_buff[MYSQL_ERRMSG_SIZE];
+      my_snprintf(warn_buff, sizeof(warn_buff), 
+                  "ORDER BY ignored as there is a user-defined clustered index"
+                  " in the table '%-.192s'", from->s->table_name.str);
+      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN, ER_UNKNOWN_ERROR,
+                   warn_buff);
+    }
+    else
+    {
+      from->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),
+                                                MYF(MY_FAE | MY_ZEROFILL));
+      bzero((char *) &tables, sizeof(tables));
+      tables.table= from;
+      tables.alias= tables.table_name= from->s->table_name.str;
+      tables.db= from->s->db.str;
+      error= 1;
 
-    if (thd->lex->select_lex.setup_ref_array(thd, order_num) ||
-	setup_order(thd, thd->lex->select_lex.ref_pointer_array,
-		    &tables, fields, all_fields, order) ||
-	!(sortorder=make_unireg_sortorder(order, &length, NULL)) ||
-	(from->sort.found_records = filesort(thd, from, sortorder, length,
-					     (SQL_SELECT *) 0, HA_POS_ERROR, 1,
-					     &examined_rows)) ==
-	HA_POS_ERROR)
-      goto err;
+      if (thd->lex->select_lex.setup_ref_array(thd, order_num) ||
+          setup_order(thd, thd->lex->select_lex.ref_pointer_array,
+                      &tables, fields, all_fields, order) ||
+          !(sortorder= make_unireg_sortorder(order, &length, NULL)) ||
+          (from->sort.found_records= filesort(thd, from, sortorder, length,
+                                              (SQL_SELECT *) 0, HA_POS_ERROR,
+                                              1, &examined_rows)) ==
+          HA_POS_ERROR)
+        goto err;
+    }
   };
 
   /* Tell handler that we have values for all columns in the to table */