MDEV-3858 Change JOIN_TAB::records_read from ha_rows to double

Currently JOIN_TAB::records_read is of type ha_rows.
This is an integer type, which prevents proper selectivity and rows estimates.

mysql-test/r/subselect_sj_mat.result

@@ -94,7 +94,7 @@ a1	a2
 explain extended
 select * from t1i where a1 in (select b1 from t2i where b1 > '0');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2i	index	it2i1,it2i3	it2i1	#	NULL	5	40.00	Using where; Using index; LooseScan
+1	PRIMARY	t2i	index	it2i1,it2i3	it2i1	#	NULL	5	50.00	Using where; Using index; LooseScan
 1	PRIMARY	t1i	ref	_it1_idx	_it1_idx	#	_ref_	1	100.00	
 Warnings:
 Note	1003	select `test`.`t1i`.`a1` AS `a1`,`test`.`t1i`.`a2` AS `a2` from `test`.`t1i` semi join (`test`.`t2i`) where ((`test`.`t1i`.`a1` = `test`.`t2i`.`b1`) and (`test`.`t2i`.`b1` > '0'))
@@ -117,7 +117,7 @@ a1	a2
 explain extended
 select * from t1i where (a1, a2) in (select b1, b2 from t2i where b1 > '0');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2i	index	it2i1,it2i2,it2i3	it2i3	#	NULL	5	40.00	Using where; Using index; LooseScan
+1	PRIMARY	t2i	index	it2i1,it2i2,it2i3	it2i3	#	NULL	5	50.00	Using where; Using index; LooseScan
 1	PRIMARY	t1i	ref	_it1_idx	_it1_idx	#	_ref_	1	100.00	
 Warnings:
 Note	1003	select `test`.`t1i`.`a1` AS `a1`,`test`.`t1i`.`a2` AS `a2` from `test`.`t1i` semi join (`test`.`t2i`) where ((`test`.`t1i`.`a2` = `test`.`t2i`.`b2`) and (`test`.`t1i`.`a1` = `test`.`t2i`.`b1`) and (`test`.`t2i`.`b1` > '0'))
@@ -319,7 +319,7 @@ where (a1, a2) in (select b1, b2 from t2i where b1 >  '0') and
 (a1, a2) in (select c1, c2 from t3i
 where (c1, c2) in (select b1, b2 from t2i where b2 > '0'));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2i	index	it2i1,it2i2,it2i3	#	#	#	5	40.00	#
+1	PRIMARY	t2i	index	it2i1,it2i2,it2i3	#	#	#	5	50.00	#
 1	PRIMARY	t1i	ref	it1i1,it1i2,it1i3	#	#	#	1	100.00	#
 1	PRIMARY	t3i	ref	it3i1,it3i2,it3i3	#	#	#	1	100.00	#
 1	PRIMARY	t2i	ref	it2i1,it2i2,it2i3	#	#	#	2	100.00	#
@@ -407,7 +407,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	MATERIALIZED	t2	ALL	NULL	#	#	#	5	100.00	#
 4	MATERIALIZED	t3	ALL	NULL	#	#	#	4	100.00	#
 3	MATERIALIZED	t3	ALL	NULL	#	#	#	4	100.00	#
-7	UNION	t2i	index	it2i1,it2i2,it2i3	#	#	#	5	40.00	#
+7	UNION	t2i	index	it2i1,it2i2,it2i3	#	#	#	5	50.00	#
 7	UNION	t1i	ref	it1i1,it1i2,it1i3	#	#	#	1	100.00	#
 7	UNION	t3i	ref	it3i1,it3i2,it3i3	#	#	#	1	100.00	#
 7	UNION	t2i	ref	it2i1,it2i2,it2i3	#	#	#	2	100.00	#

sql/item_subselect.cc

@@ -4553,7 +4553,7 @@ double get_fanout_with_deps(JOIN *join, table_map tset)
         !tab->emb_sj_nest && 
         tab->records_read != 0)
     {
-      fanout *= rows2double(tab->records_read);
+      fanout *= tab->records_read;
     }
   } 
   return fanout;

sql/sql_select.cc

@@ -6789,7 +6789,7 @@ void JOIN::get_prefix_cost_and_fanout(uint n_tables,
 
 double JOIN::get_examined_rows()
 {
-  ha_rows examined_rows;
+  double examined_rows;
   double prev_fanout= 1;
   JOIN_TAB *tab= first_breadth_first_tab(this, WALK_OPTIMIZATION_TABS);
   JOIN_TAB *prev_tab= tab;
@@ -6799,7 +6799,7 @@ double JOIN::get_examined_rows()
   while ((tab= next_breadth_first_tab(this, WALK_OPTIMIZATION_TABS, tab)))
   {
     prev_fanout *= prev_tab->records_read;
-    examined_rows+= (ha_rows) (tab->get_examined_rows() * prev_fanout);
+    examined_rows+= tab->get_examined_rows() * prev_fanout;
     prev_tab= tab;
   }
   return examined_rows;
@@ -7704,7 +7704,8 @@ get_best_combination(JOIN *join)
            sub-order
       */
       SJ_MATERIALIZATION_INFO *sjm= cur_pos->table->emb_sj_nest->sj_mat_info;
-      j->records= j->records_read= (ha_rows)(sjm->is_sj_scan? sjm->rows : 1);
+      j->records_read= sjm->is_sj_scan? sjm->rows : 1;
+      j->records= (ha_rows) j->records_read;
       JOIN_TAB *jt;
       JOIN_TAB_RANGE *jt_range;
       if (!(jt= (JOIN_TAB*)join->thd->alloc(sizeof(JOIN_TAB)*sjm->tables)) ||
@@ -7766,7 +7767,7 @@ get_best_combination(JOIN *join)
       Save records_read in JOIN_TAB so that select_describe()/etc don't have
       to access join->best_positions[]. 
     */
-    j->records_read= (ha_rows)join->best_positions[tablenr].records_read;
+    j->records_read= join->best_positions[tablenr].records_read;
     join->map2table[j->table->tablenr]= j;
 
     /* If we've reached the end of sjm nest, switch back to main sequence */
@@ -10460,7 +10461,7 @@ double JOIN_TAB::scan_time()
 
 ha_rows JOIN_TAB::get_examined_rows()
 {
-  ha_rows examined_rows;
+  double examined_rows;
 
   if (select && select->quick && use_quick != 2)
     examined_rows= select->quick->records;
@@ -10490,7 +10491,7 @@ ha_rows JOIN_TAB::get_examined_rows()
     }
   }
   else
-    examined_rows= (ha_rows) records_read; 
+    examined_rows= records_read;
 
   return examined_rows;
 }
@@ -21972,7 +21973,7 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
       }
       else
       {
-        ha_rows examined_rows= tab->get_examined_rows();
+        double examined_rows= tab->get_examined_rows();
 
         item_list.push_back(new Item_int((longlong) (ulonglong) examined_rows, 
                                          MY_INT64_NUM_DECIMAL_DIGITS));
@@ -21982,7 +21983,7 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
         {
           float f= 0.0; 
           if (examined_rows)
-            f= (float) (100.0 * tab->records_read / examined_rows);
+            f= (100.0 * (float)tab->records_read) / examined_rows;
  	  set_if_smaller(f, 100.0);
           item_list.push_back(new Item_float(f, 2));
         }

sql/sql_select.h

@@ -280,8 +280,8 @@ typedef struct st_join_table {
   */
   double        read_time;
   
-  /* psergey-todo: make the below have type double, like POSITION::records_read? */
-  ha_rows       records_read;
+  /* Copy of POSITION::records_read, set by get_best_combination() */
+  double       records_read;
   
   /* Startup cost for execution */
   double        startup_cost;