Fixed bug mdev-503.

If a table is already in the table cache but without data from persistent
statistical tables then the function open_and_process_table should not
only allocate memory for this statistical data in the corresponding
TABLE_SHARE object, but also should copy the references to the data into
certain fields of the TABLE data structure: for each key of the table 
KEY::read_stats should be copied, and for each column of the table
Field::read_stats should be copied. 

mysql-test/r/stat_tables_disabled.result

+SET SESSION STORAGE_ENGINE='InnoDB';
+select @@global.use_stat_tables;
+@@global.use_stat_tables
+NEVER
+select @@session.use_stat_tables;
+@@session.use_stat_tables
+NEVER
+set @save_use_stat_tables=@@use_stat_tables;
+set use_stat_tables='preferably';
+DROP DATABASE IF EXISTS dbt3_s001;
+CREATE DATABASE dbt3_s001;
+use dbt3_s001;
+set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='extended_keys=off';
+#
+# Bug mdev-503: optimizer ignores setting use_stat_tables='preferably'
+# 
+flush tables 
+customer, lineitem, nation, orders, part, partsupp, region, supplier;
+set use_stat_tables='never';
+EXPLAIN select sql_calc_found_rows straight_join
+l_orderkey, sum(l_extendedprice*(1-l_discount)) as revenue,
+o_orderdate, o_shippriority
+from orders, customer, lineitem
+where c_mktsegment = 'BUILDING' and c_custkey = o_custkey
+and l_orderkey = o_orderkey and o_orderdate < date '1995-03-15'
+      and l_shipdate > date '1995-03-15'
+group by l_orderkey, o_orderdate, o_shippriority
+order by revenue desc, o_orderdate
+limit 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	orders	ALL	PRIMARY,i_o_orderdate,i_o_custkey	NULL	NULL	NULL	#	Using where; Using temporary; Using filesort
+1	SIMPLE	customer	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.orders.o_custkey	#	Using where
+1	SIMPLE	lineitem	ref	PRIMARY,i_l_shipdate,i_l_orderkey,i_l_orderkey_quantity	PRIMARY	4	dbt3_s001.orders.o_orderkey	#	Using where
+set use_stat_tables='preferably';
+EXPLAIN select sql_calc_found_rows straight_join
+l_orderkey, sum(l_extendedprice*(1-l_discount)) as revenue,
+o_orderdate, o_shippriority
+from orders, customer, lineitem
+where c_mktsegment = 'BUILDING' and c_custkey = o_custkey
+and l_orderkey = o_orderkey and o_orderdate < date '1995-03-15'
+      and l_shipdate > date '1995-03-15'
+group by l_orderkey, o_orderdate, o_shippriority
+order by revenue desc, o_orderdate
+limit 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	orders	ALL	PRIMARY,i_o_orderdate,i_o_custkey	NULL	NULL	NULL	1500	Using where; Using temporary; Using filesort
+1	SIMPLE	customer	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.orders.o_custkey	1	Using where
+1	SIMPLE	lineitem	ref	PRIMARY,i_l_shipdate,i_l_orderkey,i_l_orderkey_quantity	PRIMARY	4	dbt3_s001.orders.o_orderkey	4	Using where
+flush tables customer, orders, lineitem;
+EXPLAIN select sql_calc_found_rows straight_join
+l_orderkey, sum(l_extendedprice*(1-l_discount)) as revenue,
+o_orderdate, o_shippriority
+from orders, customer, lineitem
+where c_mktsegment = 'BUILDING' and c_custkey = o_custkey
+and l_orderkey = o_orderkey and o_orderdate < date '1995-03-15'
+      and l_shipdate > date '1995-03-15'
+group by l_orderkey, o_orderdate, o_shippriority
+order by revenue desc, o_orderdate
+limit 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	orders	ALL	PRIMARY,i_o_orderdate,i_o_custkey	NULL	NULL	NULL	1500	Using where; Using temporary; Using filesort
+1	SIMPLE	customer	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.orders.o_custkey	1	Using where
+1	SIMPLE	lineitem	ref	PRIMARY,i_l_shipdate,i_l_orderkey,i_l_orderkey_quantity	PRIMARY	4	dbt3_s001.orders.o_orderkey	4	Using where
+# End of the test case for mdev-503
+set optimizer_switch=@save_optimizer_switch;
+DROP DATABASE dbt3_s001;
+use test;
+set use_stat_tables=@save_use_stat_tables;
+SET SESSION STORAGE_ENGINE=DEFAULT;

mysql-test/t/stat_tables_disabled.test

+--source include/have_innodb.inc
+
+SET SESSION STORAGE_ENGINE='InnoDB';
+
+select @@global.use_stat_tables;
+select @@session.use_stat_tables;
+
+set @save_use_stat_tables=@@use_stat_tables;
+
+set use_stat_tables='preferably';
+
+--disable_warnings
+DROP DATABASE IF EXISTS dbt3_s001;
+--enable_warnings
+
+CREATE DATABASE dbt3_s001;
+
+use dbt3_s001;
+
+set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='extended_keys=off';
+ 
+--disable_query_log
+--disable_result_log
+--disable_warnings
+--source include/dbt3_s001.inc
+delete from mysql.table_stat;
+delete from mysql.column_stat;
+delete from mysql.index_stat;
+ANALYZE TABLE
+customer, lineitem, nation, orders, part, partsupp, region, supplier;
+--enable_warnings
+--enable_result_log
+--enable_query_log
+
+--echo #
+--echo # Bug mdev-503: optimizer ignores setting use_stat_tables='preferably'
+--echo # 
+
+flush tables 
+customer, lineitem, nation, orders, part, partsupp, region, supplier;
+
+let $Q3S=
+select sql_calc_found_rows straight_join
+       l_orderkey, sum(l_extendedprice*(1-l_discount)) as revenue,
+       o_orderdate, o_shippriority
+from orders, customer, lineitem
+where c_mktsegment = 'BUILDING' and c_custkey = o_custkey
+      and l_orderkey = o_orderkey and o_orderdate < date '1995-03-15'
+      and l_shipdate > date '1995-03-15'
+group by l_orderkey, o_orderdate, o_shippriority
+order by revenue desc, o_orderdate
+limit 10;
+
+set use_stat_tables='never';
+--replace_column 9 #
+eval EXPLAIN $Q3S;
+
+set use_stat_tables='preferably';
+--replace_result 2 1
+eval EXPLAIN $Q3S;
+
+flush tables customer, orders, lineitem;
+eval EXPLAIN $Q3S;
+
+--echo # End of the test case for mdev-503
+
+set optimizer_switch=@save_optimizer_switch;
+
+
+DROP DATABASE dbt3_s001;
+
+use test;
+
+set use_stat_tables=@save_use_stat_tables;
+
+
+SET SESSION STORAGE_ENGINE=DEFAULT;

sql/sql_base.cc

@@ -4652,8 +4652,20 @@ open_and_process_table(THD *thd, LEX *lex, TABLE_LIST *tables,
     if (table_share && table_share->table_category != TABLE_CATEGORY_SYSTEM)
     {
       if (!table_share->stats_can_be_read && 
-          !alloc_statistics_for_table_share(thd, table_share, FALSE))    
+          !alloc_statistics_for_table_share(thd, table_share, FALSE))
+      {    
+        KEY *key_info= table_share->key_info;
+        KEY *key_info_end= key_info + table_share->keys;
+        KEY *table_key_info= tables->table->key_info;
+        for ( ; key_info < key_info_end; key_info++, table_key_info++)
+          table_key_info->read_stats= key_info->read_stats;
+        Field **field_ptr= table_share->field;
+        Field **table_field_ptr= tables->table->field;
+        for ( ; *field_ptr; field_ptr++, table_field_ptr++)
+          (*table_field_ptr)->read_stats= (*field_ptr)->read_stats;
+  
 	table_share->stats_can_be_read= TRUE;
+      }
 	
       if (table_share->stats_can_be_read && !table_share->stats_is_read)
       {