Added thread variable max_seeks_for_key

Change optimizer to prefer key lookups before table scan
Change table scans to be done after tables with constrains on scanned table 


mysql-test/r/distinct.result:
  Update results
mysql-test/r/group_by.result:
  Update results
mysql-test/r/heap.result:
  Update results
mysql-test/r/join.result:
  Update results
mysql-test/r/key_diff.result:
  Update results
mysql-test/r/myisam.result:
  Update results
mysql-test/r/order_by.result:
  Update results
mysql-test/r/select_safe.result:
  Update results
mysql-test/t/distinct.test:
  Change test to be repeatable
mysql-test/t/join.test:
  Change test to be repeatable
mysql-test/t/select_safe.test:
  Add tests for MAX_SEEKS_FOR_KEY
sql/handler.h:
  Optimize structure for 64 bit machines (and to avoid problems with gdb)
sql/item_cmpfunc.cc:
  Initialize not_null_tables_cache properly
sql/mysqld.cc:
  Added max_seeks_for_key
sql/set_var.cc:
  Added max_seeks_for_key
sql/sql_class.h:
  Added max_seeks_for_key
sql/sql_select.cc:
  Added max_seeks_for_key
  Change optimizer to prefer key lookups before table scan.
  Change table scans to be done after tables with constrains on scanned table

mysql-test/r/distinct.result

@@ -161,7 +161,7 @@ SELECT DISTINCT UserId FROM t1 WHERE UserId=22;
 UserId
 drop table t1;
 CREATE TABLE t1 (a int(10) unsigned not null primary key,b int(10) unsigned);
-INSERT INTO t1 VALUES (1,1),(2,1);
+INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1);
 CREATE TABLE t2 (a int(10) unsigned not null, key (A));
 INSERT INTO t2 VALUES (1),(2);
 CREATE TABLE t3 (a int(10) unsigned, key(A), b text);
@@ -189,7 +189,7 @@ insert into t4 select * from t3;
 insert into t3 select * from t4;
 explain select distinct t1.a from t1,t3 where t1.a=t3.a;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	PRIMARY	PRIMARY	4	NULL	2	Using index; Using temporary
+t1	index	PRIMARY	PRIMARY	4	NULL	4	Using index; Using temporary
 t3	ref	a	a	5	t1.a	10	Using where; Using index; Distinct
 select distinct t1.a from t1,t3 where t1.a=t3.a;
 a
@@ -200,16 +200,16 @@ select distinct 1 from t1,t3 where t1.a=t3.a;
 1
 explain SELECT distinct t1.a from t1;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	PRIMARY	4	NULL	2	Using index
+t1	index	NULL	PRIMARY	4	NULL	4	Using index
 explain SELECT distinct t1.a from t1 order by a desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	PRIMARY	4	NULL	2	Using index
+t1	index	NULL	PRIMARY	4	NULL	4	Using index
 explain SELECT t1.a from t1 group by a order by a desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	PRIMARY	4	NULL	2	Using index
+t1	index	NULL	PRIMARY	4	NULL	4	Using index
 explain SELECT distinct t1.a from t1 order by a desc limit 1;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	PRIMARY	4	NULL	2	Using index
+t1	index	NULL	PRIMARY	4	NULL	4	Using index
 explain SELECT distinct a from t3 order by a desc limit 2;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t3	index	NULL	a	5	NULL	204	Using index

mysql-test/r/group_by.result

@@ -534,11 +534,11 @@ a	b
 explain select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary; Using filesort
-t2	ALL	a	NULL	NULL	NULL	4	Using where
+t2	ALL	a	NULL	NULL	NULL	3	Using where
 explain select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b ORDER BY NULL;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary
-t2	ALL	a	NULL	NULL	NULL	4	Using where
+t2	ALL	a	NULL	NULL	NULL	3	Using where
 drop table t1,t2;
 create table t1 (a int, b int);
 insert into t1 values (1, 4),(10, 40),(1, 4),(10, 43),(1, 4),(10, 41),(1, 4),(10, 43),(1, 4);

mysql-test/r/heap.result

@@ -166,7 +166,7 @@ alter table t1 add column new_col char(1) not null, add key (btn,new_col), drop
 update t1 set new_col=btn;
 explain select * from t1 where btn="a";
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	ALL	btn	NULL	NULL	NULL	14	Using where
+t1	ALL	btn	NULL	NULL	NULL	11	Using where
 explain select * from t1 where btn="a" and new_col="a";
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ref	btn	btn	11	const,const	10	Using where

mysql-test/r/join.result

@@ -104,9 +104,7 @@ KEY category (category,county,state)
 INSERT INTO t2 VALUES (3,2,11,12,5400,7800);
 INSERT INTO t2 VALUES (4,2,25,12,6500,11200);
 INSERT INTO t2 VALUES (5,1,37,6,10000,12000);
-select a.id, b.category as catid, b.state as stateid, b.county as
-countyid from t1 a, t2 b where (a.token =
-'a71250b7ed780f6ef3185bfffe027983') and (a.count = b.id);
+select a.id, b.category as catid, b.state as stateid, b.county as countyid from t1 a, t2 b ignore index (primary) where (a.token ='a71250b7ed780f6ef3185bfffe027983') and (a.count = b.id);
 id	catid	stateid	countyid
 27	2	12	11
 28	2	12	11

mysql-test/r/key_diff.result

@@ -36,7 +36,7 @@ a	a	a	a
 explain select t1.*,t2.* from t1,t1 as t2 where t1.A=t2.B;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ALL	a	NULL	NULL	NULL	5	
-t2	ALL	b	NULL	NULL	NULL	5	Using where
+t2	ALL	b	NULL	NULL	NULL	4	Using where
 select t1.*,t2.* from t1,t1 as t2 where t1.A=t2.B order by binary t1.a,t2.a;
 a	b	a	b
 A	B	a	a

mysql-test/r/myisam.result

@@ -335,12 +335,12 @@ t1	1	c_2	1	c	A	5	NULL	NULL	YES	BTREE
 t1	1	c_2	2	a	A	5	NULL	NULL		BTREE	
 explain select * from t1,t2 where t1.a=t2.a;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	ALL	a	NULL	NULL	NULL	5	
-t2	ALL	a	NULL	NULL	NULL	2	Using where
+t2	ALL	a	NULL	NULL	NULL	2	
+t1	ALL	a	NULL	NULL	NULL	4	Using where
 explain select * from t1,t2 force index(a) where t1.a=t2.a;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t2	ALL	a	NULL	NULL	NULL	2	
-t1	ALL	a	NULL	NULL	NULL	5	Using where
+t1	ALL	a	NULL	NULL	NULL	4	Using where
 explain select * from t1 force index(a),t2 force index(a) where t1.a=t2.a;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t2	ALL	a	NULL	NULL	NULL	2	
@@ -351,8 +351,8 @@ t2	ALL	b	NULL	NULL	NULL	2
 t1	ref	b	b	5	t2.b	1	Using where
 explain select * from t1,t2 force index(c) where t1.a=t2.a;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	ALL	a	NULL	NULL	NULL	5	
-t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+t2	ALL	NULL	NULL	NULL	NULL	2	
+t1	ALL	a	NULL	NULL	NULL	4	Using where
 explain select * from t1 where a=0 or a=2;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ALL	a	NULL	NULL	NULL	5	Using where

mysql-test/r/order_by.result

@@ -307,17 +307,17 @@ table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	range	a	a	9	NULL	8	Using where; Using index
 explain select * from t1 where a = 2 and b >0 order by a desc,b desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	9	NULL	5	Using where; Using index
+t1	range	a	a	9	NULL	4	Using where; Using index
 explain select * from t1 where a = 2 and b is null order by a desc,b desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	ref	a	a	9	const,const	1	Using where; Using index; Using filesort
 explain select * from t1 where a = 2 and (b is null or b > 0) order by a
 desc,b desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	9	NULL	6	Using where; Using index
+t1	range	a	a	9	NULL	5	Using where; Using index
 explain select * from t1 where a = 2 and b > 0 order by a desc,b desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	9	NULL	5	Using where; Using index
+t1	range	a	a	9	NULL	4	Using where; Using index
 explain select * from t1 where a = 2 and b < 2 order by a desc,b desc;
 table	type	possible_keys	key	key_len	ref	rows	Extra
 t1	range	a	a	9	NULL	2	Using where; Using index

mysql-test/r/select_safe.result

 drop table if exists t1;
 SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=4, SQL_MAX_JOIN_SIZE=9;
-create table t1 (a int auto_increment primary key, b char(20));
+create table t1 (a int auto_increment primary key, b char(20), key(b));
 insert into t1 values(1,"test");
 SELECT SQL_BUFFER_RESULT * from t1;
 a	b
@@ -13,7 +13,7 @@ a	b
 1	test
 2	test2
 update t1 set b="a" where a=1;
-select 1 from t1,t1 as t2,t1 as t3,t1 as t4;
+select 1 from t1,t1 as t2,t1 as t3;
 1
 1
 1
@@ -22,11 +22,9 @@ select 1 from t1,t1 as t2,t1 as t3,t1 as t4;
 update t1 set b="a";
 You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
 update t1 set b="a" where b="test";
-You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
 delete from t1;
 You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
 delete from t1 where b="test";
-You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
 delete from t1 where a+0=1;
 You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
 select 1 from t1,t1 as t2,t1 as t3,t1 as t4,t1 as t5;
@@ -59,5 +57,22 @@ a	b
 2	test2
 4	a
 5	a
+SELECT @@MAX_SEEKS_FOR_KEY;
+@@max_seeks_for_key
+4294967295
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
+explain select * from t1,t1 as t2 where t1.b=t2.b;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ALL	b	NULL	NULL	NULL	21	
+t2	ALL	b	NULL	NULL	NULL	16	Using where
+set MAX_SEEKS_FOR_KEY=1;
+explain select * from t1,t1 as t2 where t1.b=t2.b;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ALL	b	NULL	NULL	NULL	21	
+t2	ref	b	b	21	t1.b	6	Using where
+SET MAX_SEEKS_FOR_KEY=DEFAULT;
 drop table t1;
 SET SQL_SAFE_UPDATES=0,SQL_SELECT_LIMIT=DEFAULT, SQL_MAX_JOIN_SIZE=DEFAULT;

mysql-test/t/distinct.test

@@ -60,7 +60,7 @@ drop table t1;
 #
 
 CREATE TABLE t1 (a int(10) unsigned not null primary key,b int(10) unsigned);
-INSERT INTO t1 VALUES (1,1),(2,1);
+INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1);
 CREATE TABLE t2 (a int(10) unsigned not null, key (A));
 INSERT INTO t2 VALUES (1),(2);
 CREATE TABLE t3 (a int(10) unsigned, key(A), b text);

mysql-test/t/join.test

@@ -98,10 +98,7 @@ CREATE TABLE t2 (
 INSERT INTO t2 VALUES (3,2,11,12,5400,7800);
 INSERT INTO t2 VALUES (4,2,25,12,6500,11200);
 INSERT INTO t2 VALUES (5,1,37,6,10000,12000);
-
-select a.id, b.category as catid, b.state as stateid, b.county as
-countyid from t1 a, t2 b where (a.token =
-'a71250b7ed780f6ef3185bfffe027983') and (a.count = b.id);
+select a.id, b.category as catid, b.state as stateid, b.county as countyid from t1 a, t2 b ignore index (primary) where (a.token ='a71250b7ed780f6ef3185bfffe027983') and (a.count = b.id);
 select a.id, b.category as catid, b.state as stateid, b.county as
 countyid from t1 a, t2 b where (a.token =
 'a71250b7ed780f6ef3185bfffe027983') and (a.count = b.id) order by a.id;

mysql-test/t/select_safe.test

@@ -4,7 +4,7 @@
 
 drop table if exists t1;
 SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=4, SQL_MAX_JOIN_SIZE=9;
-create table t1 (a int auto_increment primary key, b char(20));
+create table t1 (a int auto_increment primary key, b char(20), key(b));
 insert into t1 values(1,"test");
 SELECT SQL_BUFFER_RESULT * from t1;
 update t1 set b="a" where a=1;
@@ -12,7 +12,7 @@ delete from t1 where a=1;
 insert into t1 values(1,"test"),(2,"test2");
 SELECT SQL_BUFFER_RESULT * from t1;
 update t1 set b="a" where a=1;
-select 1 from t1,t1 as t2,t1 as t3,t1 as t4;
+select 1 from t1,t1 as t2,t1 as t3;
 
 # The following should give errors:
 --error 1175
@@ -49,6 +49,17 @@ SELECT * from t1;
 SET MAX_JOIN_SIZE=DEFAULT;
 SELECT * from t1;
 
+#
+# Test MAX_SEEKS_FOR_KEY
+#
+SELECT @@MAX_SEEKS_FOR_KEY;
+analyze table t1;
+insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
+explain select * from t1,t1 as t2 where t1.b=t2.b;
+set MAX_SEEKS_FOR_KEY=1;
+explain select * from t1,t1 as t2 where t1.b=t2.b;
+SET MAX_SEEKS_FOR_KEY=DEFAULT;
+
 drop table t1;
 
 SET SQL_SAFE_UPDATES=0,SQL_SELECT_LIMIT=DEFAULT, SQL_MAX_JOIN_SIZE=DEFAULT;

sql/handler.h

@@ -184,40 +184,41 @@ class handler :public Sql_alloc
 {
  protected:
   struct st_table *table;		/* The table definition */
-  uint  active_index;
 
 public:
   byte *ref;				/* Pointer to current row */
   byte *dupp_ref;			/* Pointer to dupp row */
-  uint ref_length;			/* Length of ref (1-8 or the clustered
-					key length) */
-  uint block_size;			/* index block size */
-  ha_rows records;			/* Records i datafilen */
-  ha_rows deleted;			/* Deleted records */
   ulonglong data_file_length;		/* Length off data file */
   ulonglong max_data_file_length;	/* Length off data file */
   ulonglong index_file_length;
   ulonglong max_index_file_length;
   ulonglong delete_length;		/* Free bytes */
   ulonglong auto_increment_value;
-  uint raid_type,raid_chunks;
+  ha_rows records;			/* Records in table */
+  ha_rows deleted;			/* Deleted records */
   ulong raid_chunksize;
-  uint errkey;				/* Last dup key */
-  uint sortkey, key_used_on_scan;
+  ulong mean_rec_length;		/* physical reclength */
   time_t create_time;			/* When table was created */
   time_t check_time;
   time_t update_time;
-  ulong mean_rec_length;		/* physical reclength */
+  uint errkey;				/* Last dup key */
+  uint sortkey, key_used_on_scan;
+  uint active_index;
+  /* Length of ref (1-8 or the clustered key length) */
+  uint ref_length;
+  uint block_size;			/* index block size */
+  uint raid_type,raid_chunks;
   FT_INFO *ft_handler;
   bool  auto_increment_column_changed;
 
-  handler(TABLE *table_arg) : table(table_arg),active_index(MAX_REF_PARTS),
-    ref(0),ref_length(sizeof(my_off_t)), block_size(0),records(0),deleted(0),
-    data_file_length(0), max_data_file_length(0), index_file_length(0),
-    delete_length(0), auto_increment_value(0), raid_type(0),
-    key_used_on_scan(MAX_KEY),
-    create_time(0), check_time(0), update_time(0), mean_rec_length(0),
-    ft_handler(0)
+  handler(TABLE *table_arg) :table(table_arg),
+    ref(0), data_file_length(0), max_data_file_length(0), index_file_length(0),
+    delete_length(0), auto_increment_value(0),
+    records(0), deleted(0), mean_rec_length(0),
+    create_time(0), check_time(0), update_time(0),
+    key_used_on_scan(MAX_KEY), active_index(MAX_REF_PARTS),
+    ref_length(sizeof(my_off_t)), block_size(0),
+    raid_type(0), ft_handler(0)
     {}
   virtual ~handler(void) {}
   int ha_open(const char *name, int mode, int test_if_locked);
@@ -227,7 +228,7 @@ class handler :public Sql_alloc
   uint get_dup_key(int error);
   void change_table_ptr(TABLE *table_arg) { table=table_arg; }
   virtual double scan_time()
-    { return ulonglong2double(data_file_length) / IO_SIZE + 1; }
+    { return ulonglong2double(data_file_length) / IO_SIZE + 2; }
   virtual double read_time(uint index, uint ranges, ha_rows rows)
  { return rows2double(ranges+rows); }
   virtual bool fast_key_read() { return 0;}

sql/item_cmpfunc.cc

@@ -1175,8 +1175,8 @@ Item_cond::fix_fields(THD *thd,TABLE_LIST *tables)
   List_iterator<Item> li(list);
   Item *item;
   char buff[sizeof(char*)];			// Max local vars in function
-  used_tables_cache=0;
-  const_item_cache=0;
+  not_null_tables_cache= used_tables_cache= 0;
+  const_item_cache= 0;
   /*
     and_table_cache is the value that Item_cond_or() returns for
     not_null_tables()

sql/mysqld.cc

@@ -3154,7 +3154,7 @@ enum options {
   OPT_MAX_BINLOG_CACHE_SIZE, OPT_MAX_BINLOG_SIZE,
   OPT_MAX_CONNECTIONS, OPT_MAX_CONNECT_ERRORS,
   OPT_MAX_DELAYED_THREADS, OPT_MAX_HEP_TABLE_SIZE,
-  OPT_MAX_JOIN_SIZE, OPT_MAX_SORT_LENGTH,
+  OPT_MAX_JOIN_SIZE, OPT_MAX_SORT_LENGTH, OPT_MAX_SEEKS_FOR_KEY,
   OPT_MAX_TMP_TABLES, OPT_MAX_USER_CONNECTIONS,
   OPT_MAX_WRITE_LOCK_COUNT, OPT_BULK_INSERT_BUFFER_SIZE,
   OPT_MYISAM_BLOCK_SIZE, OPT_MYISAM_MAX_EXTRA_SORT_FILE_SIZE,
@@ -3832,6 +3832,11 @@ replicating a LOAD DATA INFILE command",
    (gptr*) &global_system_variables.max_join_size,
    (gptr*) &max_system_variables.max_join_size, 0, GET_HA_ROWS, REQUIRED_ARG,
    ~0L, 1, ~0L, 0, 1, 0},
+  { "max_seeks_for_key", OPT_MAX_SEEKS_FOR_KEY,
+    "Limit assumed max number of seeks when looking up rows based on a key",
+    (gptr*) &global_system_variables.max_seeks_for_key,
+    (gptr*) &max_system_variables.max_seeks_for_key, 0, GET_ULONG,
+    REQUIRED_ARG, ~0L, 1, ~0L, 0, 1, 0 },
   {"max_sort_length", OPT_MAX_SORT_LENGTH,
    "The number of bytes to use when sorting BLOB or TEXT values (only the first max_sort_length bytes of each value are used; the rest are ignored).",
    (gptr*) &global_system_variables.max_sort_length,

sql/set_var.cc

@@ -154,6 +154,8 @@ sys_var_thd_ulong	sys_max_heap_table_size("max_heap_table_size",
 sys_var_thd_ha_rows	sys_max_join_size("max_join_size",
 					  &SV::max_join_size,
 					  fix_max_join_size);
+sys_var_thd_ulong	sys_max_seeks_for_key("max_seeks_for_key",
+					      &SV::max_seeks_for_key);
 #ifndef TO_BE_DELETED	/* Alias for max_join_size */
 sys_var_thd_ha_rows	sys_sql_max_join_size("sql_max_join_size",
 					      &SV::max_join_size,
@@ -348,6 +350,7 @@ sys_var *sys_variables[]=
   &sys_max_delayed_threads,
   &sys_max_heap_table_size,
   &sys_max_join_size,
+  &sys_max_seeks_for_key,
   &sys_max_sort_length,
   &sys_max_tmp_tables,
   &sys_max_user_connections,
@@ -492,6 +495,7 @@ struct show_var_st init_vars[]= {
   {sys_max_delayed_threads.name,(char*) &sys_max_delayed_threads,   SHOW_SYS},
   {sys_max_heap_table_size.name,(char*) &sys_max_heap_table_size,   SHOW_SYS},
   {sys_max_join_size.name,	(char*) &sys_max_join_size,	    SHOW_SYS},
+  {sys_max_seeks_for_key.name,  (char*) &sys_max_seeks_for_key,	    SHOW_SYS},
   {sys_max_sort_length.name,	(char*) &sys_max_sort_length,	    SHOW_SYS},
   {sys_max_user_connections.name,(char*) &sys_max_user_connections, SHOW_SYS},
   {sys_max_tmp_tables.name,	(char*) &sys_max_tmp_tables,	    SHOW_SYS},

sql/sql_class.h

@@ -310,6 +310,7 @@ struct system_variables
   ulong tx_isolation;
   ulong table_type;
   ulong default_week_format;
+  ulong max_seeks_for_key;
 
   my_bool log_warnings;
   my_bool low_priority_updates;

sql/sql_select.cc

@@ -1271,14 +1271,14 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
 
     /*
       Set a max range of how many seeks we can expect when using keys
-      This was (s->read_time*5), but this was too low with small rows
+      This is can't be to high as otherwise we are likely to use
+      table scan.
     */
-    s->worst_seeks= (double) s->found_records / 5;
+    s->worst_seeks= min((double) s->found_records / 10,
+			(double) s->read_time*3);
     if (s->worst_seeks < 2.0)			// Fix for small tables
       s->worst_seeks=2.0;
 
-    /* if (s->type == JT_EQ_REF)
-      continue; */
     if (s->const_keys)
     {
       ha_rows records;
@@ -1884,6 +1884,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
       best=best_time=records=DBL_MAX;
       KEYUSE *best_key=0;
       uint best_max_key_part=0;
+      my_bool found_constrain= 0;
 
       if (s->keyuse)
       {						/* Use key if possible */
@@ -1964,6 +1965,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
           }
           else
           {
+	  found_constrain= 1;
 	  /*
 	    Check if we found full key
 	  */
@@ -2000,16 +2002,18 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 		    records=2.0;		// Can't be as good as a unique
 		}
 	      }
+	      /* Limit the number of matched rows */
+	      tmp= records;
+	      set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
 	      if (table->used_keys & ((key_map) 1 << key))
 	      {
 		/* we can use only index tree */
 		uint keys_per_block= table->file->block_size/2/
 		  (keyinfo->key_length+table->file->ref_length)+1;
-		tmp=(record_count*(records+keys_per_block-1)/
-		     keys_per_block);
+		tmp=record_count*(tmp+keys_per_block-1)/keys_per_block;
 	      }
 	      else
-		tmp=record_count*min(records,s->worst_seeks);
+		tmp=record_count*min(tmp,s->worst_seeks);
 	    }
 	  }
 	  else
@@ -2039,7 +2043,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 		{
 		  /*
 		    Assume that the first key part matches 1% of the file
-		    and that the hole key matches 10 (dupplicates) or 1
+		    and that the hole key matches 10 (duplicates) or 1
 		    (unique) records.
 		    Assume also that more key matches proportionally more
 		    records
@@ -2071,6 +2075,8 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 		  records=(ulong) tmp;
 		}
 	      }
+	      /* Limit the number of matched rows */
+	      set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
 	      if (table->used_keys & ((key_map) 1 << key))
 	      {
 		/* we can use only index tree */
@@ -2113,20 +2119,31 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 	    s->table->used_keys && best_key) &&
 	  !(s->table->force_index && best_key))
       {						// Check full join
+	ha_rows rnd_records= s->found_records;
 	if (s->on_expr)
 	{
-	  tmp=rows2double(s->found_records);	// Can't use read cache
+	  tmp=rows2double(rnd_records);		// Can't use read cache
 	}
 	else
 	{
 	  tmp=(double) s->read_time;
-	  /* Calculate time to read through cache */
+	  /* Calculate time to read previous rows through cache */
 	  tmp*=(1.0+floor((double) cache_record_length(join,idx)*
 			  record_count /
 			  (double) thd->variables.join_buff_size));
 	}
+
+	/*
+	  If there is a restriction on the table, assume that 25% of the
+	  rows can be skipped on next part.
+	  This is to force tables that this table depends on before this
+	  table
+	*/
+	if (found_constrain)
+	  rnd_records-= rnd_records/4;
+
 	if (best == DBL_MAX ||
-	    (tmp  + record_count/(double) TIME_FOR_COMPARE*s->found_records <
+	    (tmp  + record_count/(double) TIME_FOR_COMPARE*rnd_records <
 	     best + record_count/(double) TIME_FOR_COMPARE*records))
 	{
 	  /*
@@ -2134,7 +2151,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 	    will ensure that this will be used
 	  */
 	  best=tmp;
-	  records= rows2double(s->found_records);
+	  records= rows2double(rnd_records);
 	  best_key=0;
 	}
       }