MDEV-18479 Another complement

This patch complements the patch that fixes bug MDEV-18479.
This patch takes care of possible overflow in JOIN::get_examined_rows().

2 files changed, 19 insertions, 16 deletions

diff --git a/mysql-test/r/derived_view.result b/mysql-test/r/derived_view.result
index d74b532d5e8..f8cf9190126 100644
--- a/mysql-test/r/derived_view.result
+++ b/mysql-test/r/derived_view.result
@@ -2942,15 +2942,15 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	p10	ALL	NULL	NULL	NULL	NULL	550	Using where; Using join buffer (incremental, BNL join)
 1	SIMPLE	<derived17>	ALL	NULL	NULL	NULL	NULL	50328437500000	Using where; Using join buffer (incremental, BNL join)
 1	SIMPLE	<derived14>	ALL	NULL	NULL	NULL	NULL	27680640625000000	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived9>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived10>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived11>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived12>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived13>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived15>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived16>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived7>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived8>	ALL	NULL	NULL	NULL	NULL	9223372036854775807	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived9>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived10>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived11>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived12>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived13>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived15>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived16>	ALL	NULL	NULL	NULL	NULL	15224352343750000640	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived7>	ALL	NULL	NULL	NULL	NULL	18446744073709551615	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	<derived8>	ALL	NULL	NULL	NULL	NULL	18446744073709551615	Using where; Using join buffer (incremental, BNL join)
 17	DERIVED	t2	system	NULL	NULL	NULL	NULL	1	
 17	DERIVED	p4	ALL	NULL	NULL	NULL	NULL	550	Using where
 17	DERIVED	p5	ALL	NULL	NULL	NULL	NULL	550	Using where; Using join buffer (flat, BNL join)
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index d7ff92a5100..a273aae5425 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -6894,17 +6894,22 @@ double JOIN::get_examined_rows()
 {
   ha_rows examined_rows;
   double prev_fanout= 1;
+  double records;
   JOIN_TAB *tab= first_breadth_first_tab(this, WALK_OPTIMIZATION_TABS);
   JOIN_TAB *prev_tab= tab;
 
-  examined_rows= tab->get_examined_rows();
+  records= tab->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);
+    prev_fanout= COST_MULT(prev_fanout, prev_tab->records_read);
+    records=
+      COST_ADD(records,
+               COST_MULT((double) (tab->get_examined_rows()), prev_fanout));
     prev_tab= tab;
   }
+  examined_rows=
+    records > (double) HA_ROWS_MAX ? HA_ROWS_MAX : (ha_rows) records;
   return examined_rows;
 }
 
@@ -10824,7 +10829,7 @@ ha_rows JOIN_TAB::get_examined_rows()
     }
   }
   else
-    examined_rows= (ha_rows) records_read;
+    examined_rows= records_read;
 
   return examined_rows;
 }
@@ -22987,9 +22992,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
       else
       {
         ha_rows examined_rows= tab->get_examined_rows();
-        ha_rows displ_rows= examined_rows;
-        set_if_smaller(displ_rows, HA_ROWS_MAX/2);
-        item_list.push_back(new Item_int((longlong) (ulonglong) displ_rows,
+        item_list.push_back(new Item_int((ulonglong) examined_rows,
                                          MY_INT64_NUM_DECIMAL_DIGITS));
 
         /* Add "filtered" field to item_list. */