Fixed bug mdev-4367.

When calculating selectivity of conditions one should take into account
the cases when some tables to be joined are empty.

mysql-test/r/selectivity.result

@@ -750,4 +750,18 @@ drop table t1;
 set histogram_size=@save_histogram_size;
 set histogram_type=@save_histogram_type;
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+#
+# Bug mdev-4367: join of a merged empty derived table 
+#                when optimizer_use_condition_selectivity=3
+#
+SET optimizer_use_condition_selectivity=3;
+CREATE TABLE t1 (a varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('j'),('k');
+CREATE TABLE t2 (b varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES ('x'),('y');
+CREATE TABLE t3 (c varchar(1), KEY(c)) ENGINE=MyISAM;
+SELECT * FROM t1 STRAIGHT_JOIN (t2 JOIN t3 ON c = b AND b > 'z');
+a	b	c
+DROP TABLE t1,t2,t3;
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 set use_stat_tables=@save_use_stat_tables;

mysql-test/r/selectivity_innodb.result

@@ -757,6 +757,20 @@ drop table t1;
 set histogram_size=@save_histogram_size;
 set histogram_type=@save_histogram_type;
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+#
+# Bug mdev-4367: join of a merged empty derived table 
+#                when optimizer_use_condition_selectivity=3
+#
+SET optimizer_use_condition_selectivity=3;
+CREATE TABLE t1 (a varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('j'),('k');
+CREATE TABLE t2 (b varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES ('x'),('y');
+CREATE TABLE t3 (c varchar(1), KEY(c)) ENGINE=MyISAM;
+SELECT * FROM t1 STRAIGHT_JOIN (t2 JOIN t3 ON c = b AND b > 'z');
+a	b	c
+DROP TABLE t1,t2,t3;
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 set use_stat_tables=@save_use_stat_tables;
 set optimizer_switch=@save_optimizer_switch_for_selectivity_test;
 SET SESSION STORAGE_ENGINE=DEFAULT;

mysql-test/t/selectivity.test

@@ -336,4 +336,26 @@ set histogram_size=@save_histogram_size;
 set histogram_type=@save_histogram_type;
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 
+--echo #
+--echo # Bug mdev-4367: join of a merged empty derived table 
+--echo #                when optimizer_use_condition_selectivity=3
+--echo #
+
+SET optimizer_use_condition_selectivity=3;
+
+CREATE TABLE t1 (a varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('j'),('k');
+
+CREATE TABLE t2 (b varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES ('x'),('y');
+
+CREATE TABLE t3 (c varchar(1), KEY(c)) ENGINE=MyISAM;
+
+SELECT * FROM t1 STRAIGHT_JOIN (t2 JOIN t3 ON c = b AND b > 'z');
+
+DROP TABLE t1,t2,t3;
+
+set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+
+
 set use_stat_tables=@save_use_stat_tables;

sql/opt_range.cc

@@ -3324,6 +3324,12 @@ bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item *cond)
   DBUG_ENTER("calculate_cond_selectivity_for_table");
 
   table->cond_selectivity= 1.0;
+
+#if 0
+#else
+  if (table_records == 0)
+    DBUG_RETURN(FALSE);
+#endif
   
   if (thd->variables.optimizer_use_condition_selectivity > 2 &&
       !bitmap_is_clear_all(used_fields))
@@ -3363,11 +3369,6 @@ bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item *cond)
       double rows;
       if (*key)
       {
-#if 0
-        rows= records_in_column_ranges(&param, idx, *key);
-        if (rows != HA_POS_ERROR)
-          (*key)->field->cond_selectivity= rows/table_records; 
-#else
         table->reginfo.impossible_range= 0;
         if ((*key)->type == SEL_ARG::IMPOSSIBLE)
 	{
@@ -3381,7 +3382,6 @@ bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item *cond)
           if (rows != HA_POS_ERROR)
             (*key)->field->cond_selectivity= rows/table_records;
         } 
-#endif
       }
     }
 

sql/sql_select.cc

@@ -3795,7 +3795,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
     */
     add_group_and_distinct_keys(join, s);
 
-    table->cond_selectivity= 1.0;
+    s->table->cond_selectivity= 1.0;
     
     /*
       Perform range analysis if there are keys it could use (1).