MDEV-18479 Complement

This patch complements the patch that fixes bug MDEV-18479.
This patch takes care of possible overflow when calculating the
estimated number of rows in a materialized derived table / view.

include/my_base.h

@@ -586,6 +586,7 @@ typedef ulong		ha_rows;
 
 #define HA_POS_ERROR	(~ (ha_rows) 0)
 #define HA_OFFSET_ERROR	(~ (my_off_t) 0)
+#define HA_ROWS_MAX        HA_POS_ERROR
 
 #if SYSTEM_SIZEOF_OFF_T == 4
 #define MAX_FILE_SIZE	INT_MAX32

mysql-test/r/derived_view.result

@@ -2641,7 +2641,7 @@ DROP TABLE t1, t2;
 set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;
 #
-# Bug mdev-12812: EXPLAIN for query with many expensive derived
+# Bug mdev-18479: EXPLAIN for query with many expensive derived
 #
 CREATE TABLE t1
 (id int auto_increment primary key,
@@ -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	<derived7>	ALL	NULL	NULL	NULL	NULL	7798774269472204288	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived8>	ALL	NULL	NULL	NULL	NULL	7798774269472204288	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived9>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived10>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived11>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived12>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived13>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived15>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	<derived16>	ALL	NULL	NULL	NULL	NULL	-3222391729959551616	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)
 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)

mysql-test/t/derived_view.test

@@ -1936,7 +1936,7 @@ set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;
 
 --echo #
---echo # Bug mdev-12812: EXPLAIN for query with many expensive derived
+--echo # Bug mdev-18479: EXPLAIN for query with many expensive derived
 --echo #
 
 CREATE TABLE t1

sql/sql_lex.cc

@@ -4100,7 +4100,10 @@ void SELECT_LEX::increase_derived_records(ha_rows records)
   DBUG_ASSERT(unit->derived);
 
   select_union *result= (select_union*)unit->result;
-  result->records+= records;
+  if (HA_ROWS_MAX - records > result->records)
+    result->records+= records;
+  else
+    result->records= HA_ROWS_MAX;
 }
 
 

sql/sql_select.cc

@@ -3830,7 +3830,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
     DBUG_RETURN(TRUE); /* purecov: inspected */
 
   {
-    ha_rows records= 1;
+    double records= 1;
     SELECT_LEX_UNIT *unit= join->select_lex->master_unit();
 
     /* Find an optimal join order of the non-constant tables. */
@@ -3855,10 +3855,14 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
         table/view.
       */
       for (i= 0; i < join->table_count ; i++)
-        records*= join->best_positions[i].records_read ?
-                  (ha_rows)join->best_positions[i].records_read : 1;
-      set_if_smaller(records, unit->select_limit_cnt);
-      join->select_lex->increase_derived_records(records);
+      {
+        records= COST_MULT(records,
+                           join->best_positions[i].records_read ?
+                           join->best_positions[i].records_read : 1);
+      }
+      ha_rows rows= records > HA_ROWS_MAX ? HA_ROWS_MAX : (ha_rows) records;
+      set_if_smaller(rows, unit->select_limit_cnt);
+      join->select_lex->increase_derived_records(rows);
     }
   }
 
@@ -10795,7 +10799,7 @@ ha_rows JOIN_TAB::get_examined_rows()
     }
   }
   else
-    examined_rows= (ha_rows) records_read; 
+    examined_rows= (ha_rows) records_read;
 
   return examined_rows;
 }
@@ -22924,8 +22928,9 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
       else
       {
         ha_rows examined_rows= tab->get_examined_rows();
-
-        item_list.push_back(new Item_int((longlong) (ulonglong) 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,
                                          MY_INT64_NUM_DECIMAL_DIGITS));
 
         /* Add "filtered" field to item_list. */