Fixes for 'Filtering'

- table_after_join_selectivity() should use records_init (new bug)
- get_examined_rows() changed to double to get similar results
  as in MariaDB 10.11
- Fixed bug where table_after_join_selectivity() did not correct
  selectivity in the case where a RANGE is used instead of a REF.
  This can happen if the range can use more key_parts than the REF.
  WHERE key_part1=10 and key_part2 < 10

Other things:
- Use JT_RANGE instead of JT_ALL for RANGE access in all parts of the code.
  Before we used JT_ALL for RANGE.
- Force RANGE be used in best_access_path() if the range used more key
  parts than ref. In the original code, this was done much later in
  make_join_select)(). However we need to know in
  table_after_join_selectivity() if we have used RANGE or not.
- Added more information about filtering to optimizer_trace.

mysql-test/main/selectivity.result

@@ -1808,6 +1808,18 @@ b	a	a	b
 7	7	8	8
 8	8	9	9
 9	9	10	10
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+explain extended select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	10	NULL	9	100.00	Using index condition; Using where
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.c	1	100.00	Using index
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.d	1	100.00	
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t1`.`c` and `test`.`t3`.`a` = `test`.`t1`.`d` and `test`.`t1`.`a` = 50 and `test`.`t1`.`b` <= 100
 set optimizer_use_condition_selectivity= @@optimizer_use_condition_selectivity;
 drop table t1,t2,t3;
 #

mysql-test/main/selectivity.test

@@ -1234,6 +1234,8 @@ eval $query;
 set optimizer_use_condition_selectivity=2;
 eval explain extended $query;
 eval $query;
+analyze table t1;
+eval explain extended $query;
 set optimizer_use_condition_selectivity= @@optimizer_use_condition_selectivity;
 
 drop table t1,t2,t3;

sql/opt_subselect.cc

@@ -4149,6 +4149,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
              */
              if (join->best_positions[idx].key)
              {
+               DBUG_ASSERT(join->best_positions[idx].type != JT_RANGE);
                delete join->best_positions[idx].table->quick;
                join->best_positions[idx].table->quick= NULL;
              }