Bug #14200010 NEWLY CREATED TABLE DOESN'T ALLOW FOR LOOSE INDEX SCANS

Problem:

Before the ALTER TABLE statement, the array
dict_index_t::stat_n_diff_key_vals had proper values calculated
and updated.  But after the ALTER TABLE statement, all the values
of this array is 0.  

Because of this statistics returned by innodb_rec_per_key() is
different before and after the ALTER TABLE statement. Running the
ANALYZE TABLE command populates the statistics correctly.

Solution:

After ALTER TABLE statement, set the flag dict_table_t::stat_initialized
correctly so that the table statistics will be recalculated properly when
the table is next loaded.  But note that we still don't choose the loose
index scans.  This fix only ensures that an ALTER TABLE does not change
the optimizer plan.

rb://1639 approved by Marko and Jimmy.

mysql-test/suite/innodb_plugin/r/innodb-index.result

@@ -963,7 +963,7 @@ Table	Op	Msg_type	Msg_text
 test.t1	check	status	OK
 explain select * from t1 where b like 'adfd%';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	b	NULL	NULL	NULL	15	Using where
+1	SIMPLE	t1	range	b	b	769	NULL	7	Using where
 create table t2(a int, b varchar(255), primary key(a,b)) engine=innodb;
 insert into t2 select a,left(b,255) from t1;
 drop table t1;

mysql-test/suite/innodb_plugin/r/innodb_mysql.result

@@ -343,7 +343,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	NULL	PRIMARY	5	NULL	4	Using index; Using temporary
 explain select distinct f1, f2 from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	NULL	PRIMARY	5	NULL	3	Using index for group-by; Using temporary
+1	SIMPLE	t1	index	NULL	PRIMARY	5	NULL	4	Using index
 drop table t1;
 CREATE TABLE t1 (id int(11) NOT NULL PRIMARY KEY, name varchar(20),
 INDEX (name));

storage/innodb_plugin/row/row0mysql.c

@@ -4083,6 +4083,13 @@ end:
 			trx->error_state = DB_SUCCESS;
 			trx_general_rollback_for_mysql(trx, NULL);
 			trx->error_state = DB_SUCCESS;
+		} else {
+			if (old_is_tmp && !new_is_tmp) {
+				/* After ALTER TABLE the table statistics
+				needs to be rebuilt.  It will be rebuilt
+				when the table is loaded again. */
+				table->stat_initialized = FALSE;
+			}
 		}
 	}