Added EQ_REF chaining to the greedy_optimizer

MDEV-28073 Slow query performance in MariaDB when using many table

The idea is to prefer and chain EQ_REF tables (tables that uses an
unique key to find a row) when searching for the best table combination.
This significantly reduces row combinations that has to be examined.
This is optimization is enabled when setting optimizer_prune_level=2
(which is now default).

Implementation:
- optimizer_prune_level has a new level, 2, which enables EQ_REF
  optimization in addition to the pruning done by level 1.
  Level 2 is now default.
- Added JOIN::eq_ref_tables that contains bits of tables that could use
  potentially use EQ_REF access in the query.  This is calculated
  in sort_and_filter_keyuse()

Under optimizer_prune_level=2:
- When the greedy_optimizer notices that the preceding table was an
  EQ_REF table, it tries to add an EQ_REF table next. If an EQ_REF
  table exists, only this one will be considered at this level.
  We also collect all EQ_REF tables chained by the next levels and these
  are ignored on the starting level as we have already examined these.
  If no EQ_REF table exists, we continue as normal.

This optimization speeds up the greedy_optimizer combination test with
~25%

Other things:
- I ported the changes in MySQL 5.7 to greedy_optimizer.test to MariaDB
  to be able to ensure we can handle all cases that MySQL can do.
- I have run all tests with --mysqld=--optimizer_prune_level=1 to verify that
  there where no test changes.

mysql-test/include/check_qep.inc

+# include/check_qep.inc
+#
+# SUMMARY
+#
+#    Designed to be used together with include/expect_qep.inc
+#
+#    $query should be assigned a select statement using
+#    straight_join to force the tables to be joined in most
+#    optimal order.
+#
+#    expect_qep.inc will then store the estimated 'Last_query_cost'
+#    and total # 'Handler_read%' for this straight_joined query.
+#
+#    We should then assign a non-straight_join'ed version of
+#    the same query to $query and execute it using
+#    'include/check_qep.inc'. Its estimated cost and
+#    #handler_reads will then be verified against the
+#    previous straight_joined query.
+#
+# USAGE
+#
+#    let $query= <select straight_join optimal statement>;
+#    --source include/expect_qep.inc
+#    let $query= <select statement>;
+#    --source include/check_qep.inc
+#
+# EXAMPLE
+#    t/greedy_optimizer.test
+#
+
+flush status;
+eval EXPLAIN $query;
+eval $query;
+
+let $cost=
+ query_get_value(SHOW STATUS LIKE 'Last_query_cost', Value, 1);
+
+--disable_warnings
+let $reads=
+`select sum(variable_value)
+   from information_schema.session_status
+   where VARIABLE_NAME like 'Handler_read%'`;
+--enable_warnings
+
+#echo Cost: $cost, Handler_reads: $reads;
+
+if ($cost != $best_cost)
+{ echo ### FAILED: Query_cost: $cost, expected: $best_cost ###;
+}
+# Difference in handler reads are ok as tables in MariaDB are sorted according
+# to order in the query and the tables in greedy_optimizer.inc has reference to
+# rows that does not exists, so different table orders will do different
+# number of reads
+
+if ($reads != $best_reads)
+{ echo ### NOTE: Handler_reads: $reads, expected: $best_reads ###;
+}

mysql-test/include/execute_with_statistics.inc

+# include/execute_with_statistics.inc
+#
+# SUMMARY
+#
+#    Explain and execute the select statment in $query.
+#    Then report 'Last_query_cost' estimate from the query
+#    optimizer and total number of 'Handler_read%' when the
+#    query was executed.
+#    Intended usage is to verify that there are not regressions
+#    in either calculated or actuall cost for $query.
+#
+# USAGE
+#
+#    let $query= <select statement>;
+#    --source include/execute_with_statistics.inc
+#
+# EXAMPLE
+#    t/greedy_optimizer.test
+#
+
+eval EXPLAIN $query;
+SHOW STATUS LIKE 'Last_query_cost';
+
+FLUSH STATUS;
+eval $query;
+--disable_warnings
+SELECT SUM(variable_value) AS Total_handler_reads
+   FROM information_schema.session_status
+   WHERE variable_name LIKE 'Handler_read%';
+--enable_warnings

mysql-test/include/expect_qep.inc

+# include/expect_qep.inc
+#
+# SUMMARY
+#
+#    Designed to be used together with include/check_qep.inc
+#
+#    $query should be assigned a select statement using
+#    straight_join to force the tables to be joined in most
+#    optimal order.
+#
+#    expect_qep.inc will then store the estimated 'Last_query_cost'
+#    and total # 'Handler_read%' for this straight_joined query.
+#
+#    We should then assign a non-straight_join'ed version of
+#    the same query to $query and execute it using
+#    'include/check_qep.inc'. Its estimated cost and
+#    #handler_reads will then be verified against the
+#    previous straight_joined query.
+#
+# USAGE
+#
+#    let $query= <select straight_join optimal statement>;
+#    --source include/expect_qep.inc
+#    let $query= <select statement>;
+#    --source include/check_qep.inc
+#
+# EXAMPLE
+#    t/greedy_optimizer.test
+#
+
+flush status;
+eval EXPLAIN $query;
+eval $query;
+
+let $best_cost=
+  query_get_value(SHOW STATUS LIKE 'Last_query_cost', Value, 1);
+
+--disable_warnings
+let $best_reads=
+`select sum(variable_value)
+   from information_schema.session_status
+   where VARIABLE_NAME like 'Handler_read%'`;
+--enable_warnings
+
+#echo Expect, cost: $best_cost, Handler_reads: $best_reads;

mysql-test/main/join.result

@@ -890,7 +890,7 @@ insert into t2 select @v:=A.a+10*B.a, @v  from t1 A, t1 B;
 explain select * from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	
-show status like '%cost%';
+show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	4.016090
 select 'The cost of accessing t1 (dont care if it changes' '^';
@@ -904,7 +904,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
 1	SIMPLE	A	eq_ref	PRIMARY	PRIMARY	4	test.t1.a	1	Using where
 1	SIMPLE	B	eq_ref	PRIMARY	PRIMARY	4	test.A.b	1	
-show status like '%cost%';
+show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	28.016090
 select '^^: The above should be ~= 20 + cost(select * from t1). Value less than 20 is an error' Z;

mysql-test/main/join.test

@@ -692,13 +692,13 @@ create table t2 (a int, b int, primary key(a));
 insert into t2 select @v:=A.a+10*B.a, @v  from t1 A, t1 B;
 
 explain select * from t1;
-show status like '%cost%';
+show status like 'Last_query_cost';
 select 'The cost of accessing t1 (dont care if it changes' '^';
 
 select 'vv: Following query must use ALL(t1), eq_ref(A), eq_ref(B): vv' Z;
 
 explain select * from t1, t2 A, t2 B where A.a = t1.a and B.a=A.b;
-show status like '%cost%';
+show status like 'Last_query_cost';
 select '^^: The above should be ~= 20 + cost(select * from t1). Value less than 20 is an error' Z;
 
 

mysql-test/main/join_nested.result

@@ -1744,9 +1744,9 @@ ON t4.carrier = t1.carrier;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	index	package_id	package_id	5	NULL	45	Using where; Using index
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.package_id	1	
-1	SIMPLE	t3	ref	package_id	package_id	5	test.t2.package_id	1	Using index
 1	SIMPLE	t4	eq_ref	PRIMARY,id	PRIMARY	2	test.t1.carrier	1	Using where
 1	SIMPLE	t5	ref	carrier_id	carrier_id	5	test.t4.id	22	Using index
+1	SIMPLE	t3	ref	package_id	package_id	5	test.t2.package_id	1	Using index
 SELECT COUNT(*) 
 FROM ((t2 JOIN t1 ON t2.package_id = t1.id) 
 JOIN t3 ON t3.package_id = t1.id)

mysql-test/main/join_nested_jcl6.result

@@ -1753,9 +1753,9 @@ ON t4.carrier = t1.carrier;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	index	package_id	package_id	5	NULL	45	Using where; Using index
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.package_id	1	Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
-1	SIMPLE	t3	ref	package_id	package_id	5	test.t2.package_id	1	Using index
 1	SIMPLE	t4	eq_ref	PRIMARY,id	PRIMARY	2	test.t1.carrier	1	Using where
 1	SIMPLE	t5	ref	carrier_id	carrier_id	5	test.t4.id	22	Using index
+1	SIMPLE	t3	ref	package_id	package_id	5	test.t2.package_id	1	Using index
 SELECT COUNT(*) 
 FROM ((t2 JOIN t1 ON t2.package_id = t1.id) 
 JOIN t3 ON t3.package_id = t1.id)

mysql-test/main/join_outer_innodb.result

@@ -437,15 +437,15 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	a4,a6,a5,a7	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ref	PRIMARY	PRIMARY	4	test.t1.a1	1	Using index
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.b2	1	Using where; Using index
+1	SIMPLE	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
 1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	4	test.t1.a2	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.d1	1	Using where
 1	SIMPLE	t6	eq_ref	PRIMARY	PRIMARY	4	test.t1.a3	1	Using where; Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	1	
-1	SIMPLE	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
-1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	t11	eq_ref	PRIMARY	PRIMARY	4	test.t1.a5	1	
 1	SIMPLE	t12	eq_ref	PRIMARY	PRIMARY	4	test.t11.k3	1	Using where
 1	SIMPLE	l2	eq_ref	PRIMARY	PRIMARY	4	test.t11.k4	1	Using where
+1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	t13	ref	PRIMARY,m3	m3	8	const,test.t1.a1	1	Using index
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where; Using index
 1	SIMPLE	m2	ref	PRIMARY,m3	m3	8	const,test.t1.a1	1	Using index
@@ -459,15 +459,15 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	a4,a6,a5,a7	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ref	PRIMARY	PRIMARY	4	test.t1.a1	1	Using index
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.b2	1	Using where; Using index
+1	SIMPLE	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
 1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	4	test.t1.a2	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.d1	1	Using where
 1	SIMPLE	t6	eq_ref	PRIMARY	PRIMARY	4	test.t1.a3	1	Using where; Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	1	
-1	SIMPLE	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
-1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	t11	eq_ref	PRIMARY	PRIMARY	4	test.t1.a5	1	
 1	SIMPLE	t12	eq_ref	PRIMARY	PRIMARY	4	test.t11.k3	1	Using where
 1	SIMPLE	l2	eq_ref	PRIMARY	PRIMARY	4	test.t11.k4	1	Using where
+1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	t13	ref	PRIMARY,m3	m3	8	const,test.t1.a1	1	Using index
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where; Using index
 1	SIMPLE	m2	ref	PRIMARY,m3	m3	8	const,test.t1.a1	1	Using index

mysql-test/main/mysqld--help.result

@@ -706,8 +706,9 @@ The following specify which files/extra groups are read (specified before remain
  Controls the heuristic(s) applied during query
  optimization to prune less-promising partial plans from
  the optimizer search space. Meaning: 0 - do not apply any
- heuristic, thus perform exhaustive search; 1 - prune
- plans based on number of retrieved rows
+ heuristic, thus perform exhaustive search: 1 - prune
+ plans based on cost and number of retrieved rows eq_ref:
+ 2 - prune also if we find an eq_ref chain
  --optimizer-search-depth=# 
  Maximum depth of search performed by the query optimizer.
  Values larger than the number of relations in a query
@@ -1662,7 +1663,7 @@ old-mode UTF8_IS_UTF8MB3
 old-passwords FALSE
 old-style-user-limits FALSE
 optimizer-max-sel-arg-weight 32000
-optimizer-prune-level 1
+optimizer-prune-level 2
 optimizer-search-depth 62
 optimizer-selectivity-sampling-limit 100
 optimizer-switch index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=on,condition_pushdown_for_derived=on,split_materialized=on,condition_pushdown_for_subquery=on,rowid_filter=on,condition_pushdown_from_having=on

mysql-test/main/opt_trace.test

@@ -888,3 +888,4 @@ select left(trace, 100) from information_schema.optimizer_trace;
 set optimizer_trace='enabled=off';
 
 --echo # End of 10.6 tests
+

mysql-test/main/opt_trace_index_merge.result

@@ -203,23 +203,27 @@ explain select * from t1 where a=1 or b=1	{
             "considered_execution_plans": [
               {
                 "plan_prefix": [],
-                "table": "t1",
-                "best_access_path": {
-                  "considered_access_paths": [
-                    {
-                      "access_type": "index_merge",
-                      "resulting_rows": 2,
-                      "cost": 2.484903732,
-                      "chosen": true
+                "get_costs_for_tables": [
+                  {
+                    "best_access_path": {
+                      "table": "t1",
+                      "considered_access_paths": [
+                        {
+                          "access_type": "index_merge",
+                          "resulting_rows": 2,
+                          "cost": 2.484903732,
+                          "chosen": true
+                        }
+                      ],
+                      "chosen_access_method": {
+                        "type": "index_merge",
+                        "records": 2,
+                        "cost": 2.484903732,
+                        "uses_join_buffering": false
+                      }
                     }
-                  ],
-                  "chosen_access_method": {
-                    "type": "index_merge",
-                    "records": 2,
-                    "cost": 2.484903732,
-                    "uses_join_buffering": false
                   }
-                }
+                ]
               },
               {
                 "plan_prefix": [],

mysql-test/main/opt_trace_index_merge_innodb.result

@@ -202,37 +202,40 @@ explain select * from t1 where pk1 != 0  and key1 = 1	{
             "considered_execution_plans": [
               {
                 "plan_prefix": [],
-                "table": "t1",
-                "best_access_path": {
-                  "considered_access_paths": [
-                    {
-                      "access_type": "ref",
-                      "index": "key1",
-                      "used_range_estimates": true,
-                      "rows": 1,
-                      "cost": 1.125146475,
-                      "chosen": true
-                    },
-                    {
-                      "type": "scan",
-                      "chosen": false,
-                      "cause": "cost"
+                "get_costs_for_tables": [
+                  {
+                    "best_access_path": {
+                      "table": "t1",
+                      "considered_access_paths": [
+                        {
+                          "access_type": "ref",
+                          "index": "key1",
+                          "used_range_estimates": true,
+                          "rows": 1,
+                          "cost": 1.125146475,
+                          "chosen": true
+                        },
+                        {
+                          "type": "scan",
+                          "chosen": false,
+                          "cause": "cost"
+                        }
+                      ],
+                      "chosen_access_method": {
+                        "type": "ref",
+                        "records": 1,
+                        "cost": 1.125146475,
+                        "uses_join_buffering": false
+                      }
                     }
-                  ],
-                  "chosen_access_method": {
-                    "type": "ref",
-                    "records": 1,
-                    "cost": 1.125146475,
-                    "uses_join_buffering": false
                   }
-                }
+                ]
               },
               {
                 "plan_prefix": [],
                 "table": "t1",
                 "rows_for_plan": 1,
-                "cost_for_plan": 1.325146475,
-                "pruned_by_hanging_leaf": true
+                "cost_for_plan": 1.325146475
               }
             ]
           },

mysql-test/main/opt_trace_security.result

@@ -89,23 +89,27 @@ select * from db1.t1	{
             "considered_execution_plans": [
               {
                 "plan_prefix": [],
-                "table": "t1",
-                "best_access_path": {
-                  "considered_access_paths": [
-                    {
-                      "access_type": "scan",
-                      "resulting_rows": 3,
-                      "cost": 2.005126953,
-                      "chosen": true
+                "get_costs_for_tables": [
+                  {
+                    "best_access_path": {
+                      "table": "t1",
+                      "considered_access_paths": [
+                        {
+                          "access_type": "scan",
+                          "resulting_rows": 3,
+                          "cost": 2.005126953,
+                          "chosen": true
+                        }
+                      ],
+                      "chosen_access_method": {
+                        "type": "scan",
+                        "records": 3,
+                        "cost": 2.005126953,
+                        "uses_join_buffering": false
+                      }
                     }
-                  ],
-                  "chosen_access_method": {
-                    "type": "scan",
-                    "records": 3,
-                    "cost": 2.005126953,
-                    "uses_join_buffering": false
                   }
-                }
+                ]
               },
               {
                 "plan_prefix": [],
@@ -214,23 +218,27 @@ select * from db1.v1	{
             "considered_execution_plans": [
               {
                 "plan_prefix": [],
-                "table": "t1",
-                "best_access_path": {
-                  "considered_access_paths": [
-                    {
-                      "access_type": "scan",
-                      "resulting_rows": 3,
-                      "cost": 2.005126953,
-                      "chosen": true
+                "get_costs_for_tables": [
+                  {
+                    "best_access_path": {
+                      "table": "t1",
+                      "considered_access_paths": [
+                        {
+                          "access_type": "scan",
+                          "resulting_rows": 3,
+                          "cost": 2.005126953,
+                          "chosen": true
+                        }
+                      ],
+                      "chosen_access_method": {
+                        "type": "scan",
+                        "records": 3,
+                        "cost": 2.005126953,
+                        "uses_join_buffering": false
+                      }
                     }
-                  ],
-                  "chosen_access_method": {
-                    "type": "scan",
-                    "records": 3,
-                    "cost": 2.005126953,
-                    "uses_join_buffering": false
                   }
-                }
+                ]
               },
               {
                 "plan_prefix": [],

mysql-test/main/selectivity_innodb.result

@@ -1257,8 +1257,8 @@ EXPLAIN EXTENDED
 SELECT * FROM language, country, continent
 WHERE country_group = lang_group AND lang_group IS NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	language	ALL	NULL	NULL	NULL	NULL	6	0.00	Using where
-1	SIMPLE	country	ALL	NULL	NULL	NULL	NULL	2	0.00	Using where; Using join buffer (flat, BNL join)
+1	SIMPLE	language	ALL	NULL	NULL	NULL	NULL	6	16.67	Using where
+1	SIMPLE	country	ALL	NULL	NULL	NULL	NULL	2	50.00	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	continent	ALL	NULL	NULL	NULL	NULL	6	100.00	Using join buffer (incremental, BNL join)
 Warnings:
 Note	1003	select `test`.`language`.`lang_group` AS `lang_group`,`test`.`language`.`lang` AS `lang`,`test`.`country`.`code` AS `code`,`test`.`country`.`country_group` AS `country_group`,`test`.`continent`.`cont_group` AS `cont_group`,`test`.`continent`.`cont` AS `cont` from `test`.`language` join `test`.`country` join `test`.`continent` where `test`.`country`.`country_group` = `test`.`language`.`lang_group` and `test`.`language`.`lang_group` is null

mysql-test/main/stat_tables.result

@@ -216,10 +216,10 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	part	ALL	PRIMARY	NULL	NULL	NULL	200	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	lineitem	ref	PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity	i_l_partkey	5	dbt3_s001.part.p_partkey	30	Using where
 1	SIMPLE	supplier	eq_ref	PRIMARY,i_s_nationkey	PRIMARY	4	dbt3_s001.lineitem.l_suppkey	1	Using where
+1	SIMPLE	n2	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.supplier.s_nationkey	1	
 1	SIMPLE	orders	eq_ref|filter	PRIMARY,i_o_orderdate,i_o_custkey	PRIMARY|i_o_orderdate	4|4	dbt3_s001.lineitem.l_orderkey	1 (27%)	Using where; Using rowid filter
 1	SIMPLE	customer	eq_ref	PRIMARY,i_c_nationkey	PRIMARY	4	dbt3_s001.orders.o_custkey	1	Using where
 1	SIMPLE	n1	eq_ref	PRIMARY,i_n_regionkey	PRIMARY	4	dbt3_s001.customer.c_nationkey	1	Using where
-1	SIMPLE	n2	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.supplier.s_nationkey	1	
 select o_year,
 sum(case when nation = 'UNITED STATES' then volume else 0 end) /
 sum(volume) as mkt_share

mysql-test/main/stat_tables_innodb.result

@@ -248,10 +248,10 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	part	ALL	PRIMARY	NULL	NULL	NULL	200	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	lineitem	ref	PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity	i_l_partkey	5	dbt3_s001.part.p_partkey	30	Using where
 1	SIMPLE	supplier	eq_ref	PRIMARY,i_s_nationkey	PRIMARY	4	dbt3_s001.lineitem.l_suppkey	1	Using where
+1	SIMPLE	n2	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.supplier.s_nationkey	1	
 1	SIMPLE	orders	eq_ref	PRIMARY,i_o_orderdate,i_o_custkey	PRIMARY	4	dbt3_s001.lineitem.l_orderkey	1	Using where
 1	SIMPLE	customer	eq_ref	PRIMARY,i_c_nationkey	PRIMARY	4	dbt3_s001.orders.o_custkey	1	Using where
 1	SIMPLE	n1	eq_ref	PRIMARY,i_n_regionkey	PRIMARY	4	dbt3_s001.customer.c_nationkey	1	Using where
-1	SIMPLE	n2	eq_ref	PRIMARY	PRIMARY	4	dbt3_s001.supplier.s_nationkey	1	
 select o_year,
 sum(case when nation = 'UNITED STATES' then volume else 0 end) /
 sum(volume) as mkt_share

mysql-test/main/subselect2.result

@@ -120,19 +120,19 @@ ALTER TABLE t2 ADD  FOREIGN KEY FK_DCMNTS_FLDRS ( FOLDERID)
 REFERENCES t3 (FOLDERID );
 ALTER TABLE t3 ADD  FOREIGN KEY FK_FLDRS_PRNTID ( PARENTID)
 REFERENCES t3 (FOLDERID );
-SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3.FOLDERNAME = 'Level1') AND t3.FOLDERNAME = 'Level2') AND t3.FOLDERNAME = 'Level3') AND t3.FOLDERNAME = 'CopiedFolder') AND t3.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
+SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3_a.FOLDERID FROM t3 as t3_a WHERE t3_a.PARENTID IN(SELECT t3_b.FOLDERID FROM t3 as t3_b WHERE t3_b.PARENTID IN(SELECT t3_c.FOLDERID FROM t3 as t3_c WHERE t3_c.PARENTID IN(SELECT t3_d.FOLDERID FROM t3 as t3_d WHERE t3_d.PARENTID IN(SELECT t3_e.FOLDERID FROM t3 as t3_e WHERE t3_e.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3_e.FOLDERNAME = 'Level1') AND t3_d.FOLDERNAME = 'Level2') AND t3_c.FOLDERNAME = 'Level3') AND t3_b.FOLDERNAME = 'CopiedFolder') AND t3_a.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
 DOCID	DOCNAME	DOCTYPEID	FOLDERID	AUTHOR	CREATED	TITLE	SUBTITLE	DOCABSTRACT	PUBLISHDATE	EXPIRATIONDATE	LOCKEDBY	STATUS	PARENTDOCID	REPID	MODIFIED	MODIFIER	PUBLISHSTATUS	ORIGINATOR	DOCTYPENAME	CONTENTSIZE	MIMETYPE
 c373e9f5ad07993f3859444553544200	Last Discussion	c373e9f5ad079174ff17444553544200	c373e9f5ad0796c0eca4444553544200	Goldilocks	2003-06-09 11:21:06	Title: Last Discussion	NULL	Setting new abstract and keeping doc checked out	2003-06-09 10:51:26	2003-06-09 10:51:26	NULL	NULL	NULL	03eea05112b845949f3fd03278b5fe43	2003-06-09 11:21:06	admin	0	NULL	Discussion	NULL	NULL
-EXPLAIN SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3.FOLDERNAME = 'Level1') AND t3.FOLDERNAME = 'Level2') AND t3.FOLDERNAME = 'Level3') AND t3.FOLDERNAME = 'CopiedFolder') AND t3.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
+EXPLAIN SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3_a.FOLDERID FROM t3 as t3_a WHERE t3_a.PARENTID IN(SELECT t3_b.FOLDERID FROM t3 as t3_b WHERE t3_b.PARENTID IN(SELECT t3_c.FOLDERID FROM t3 as t3_c WHERE t3_c.PARENTID IN(SELECT t3_d.FOLDERID FROM t3 as t3_d WHERE t3_d.PARENTID IN(SELECT t3_e.FOLDERID FROM t3 as t3_e WHERE t3_e.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3_e.FOLDERNAME = 'Level1') AND t3_d.FOLDERNAME = 'Level2') AND t3_c.FOLDERNAME = 'Level3') AND t3_b.FOLDERNAME = 'CopiedFolder') AND t3_a.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	DDOCTYPEID_IDX,DFOLDERID_IDX	NULL	NULL	NULL	9	Using where
 1	PRIMARY	t4	eq_ref	PRIMARY	PRIMARY	34	test.t2.DOCTYPEID	1	
 1	PRIMARY	t1	eq_ref	PRIMARY	PRIMARY	34	test.t2.DOCID	1	
-1	PRIMARY	t3	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t2.FOLDERID	1	Using where
-1	PRIMARY	t3	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3.PARENTID	1	Using where
-1	PRIMARY	t3	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3.PARENTID	1	Using where
-1	PRIMARY	t3	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3.PARENTID	1	Using where
-1	PRIMARY	t3	ref|filter	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	FFOLDERID_IDX|CMFLDRPARNT_IDX	34|35	test.t3.PARENTID	1 (29%)	Using where; Using rowid filter
+1	PRIMARY	t3_a	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t2.FOLDERID	1	Using where
+1	PRIMARY	t3_b	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3_a.PARENTID	1	Using where
+1	PRIMARY	t3_c	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3_b.PARENTID	1	Using where
+1	PRIMARY	t3_d	eq_ref	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	PRIMARY	34	test.t3_c.PARENTID	1	Using where
+1	PRIMARY	t3_e	ref|filter	PRIMARY,FFOLDERID_IDX,CMFLDRPARNT_IDX	FFOLDERID_IDX|CMFLDRPARNT_IDX	34|35	test.t3_d.PARENTID	1 (29%)	Using where; Using rowid filter
 drop table t1, t2, t3, t4;
 CREATE TABLE t1 (a int(10) , PRIMARY KEY (a)) Engine=InnoDB;
 INSERT INTO t1 VALUES (1),(2);

mysql-test/main/subselect2.test

@@ -148,9 +148,9 @@ ALTER TABLE t2 ADD  FOREIGN KEY FK_DCMNTS_FLDRS ( FOLDERID)
 ALTER TABLE t3 ADD  FOREIGN KEY FK_FLDRS_PRNTID ( PARENTID)
     REFERENCES t3 (FOLDERID );
 
-SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3.FOLDERNAME = 'Level1') AND t3.FOLDERNAME = 'Level2') AND t3.FOLDERNAME = 'Level3') AND t3.FOLDERNAME = 'CopiedFolder') AND t3.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
+SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3_a.FOLDERID FROM t3 as t3_a WHERE t3_a.PARENTID IN(SELECT t3_b.FOLDERID FROM t3 as t3_b WHERE t3_b.PARENTID IN(SELECT t3_c.FOLDERID FROM t3 as t3_c WHERE t3_c.PARENTID IN(SELECT t3_d.FOLDERID FROM t3 as t3_d WHERE t3_d.PARENTID IN(SELECT t3_e.FOLDERID FROM t3 as t3_e WHERE t3_e.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3_e.FOLDERNAME = 'Level1') AND t3_d.FOLDERNAME = 'Level2') AND t3_c.FOLDERNAME = 'Level3') AND t3_b.FOLDERNAME = 'CopiedFolder') AND t3_a.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
 
-EXPLAIN SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID IN(SELECT t3.FOLDERID FROM t3 WHERE t3.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3.FOLDERNAME = 'Level1') AND t3.FOLDERNAME = 'Level2') AND t3.FOLDERNAME = 'Level3') AND t3.FOLDERNAME = 'CopiedFolder') AND t3.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
+EXPLAIN SELECT t2.*, t4.DOCTYPENAME, t1.CONTENTSIZE,t1.MIMETYPE FROM t2 INNER JOIN t4 ON t2.DOCTYPEID = t4.DOCTYPEID LEFT OUTER JOIN t1 ON t2.DOCID = t1.DOCID WHERE t2.FOLDERID IN(SELECT t3_a.FOLDERID FROM t3 as t3_a WHERE t3_a.PARENTID IN(SELECT t3_b.FOLDERID FROM t3 as t3_b WHERE t3_b.PARENTID IN(SELECT t3_c.FOLDERID FROM t3 as t3_c WHERE t3_c.PARENTID IN(SELECT t3_d.FOLDERID FROM t3 as t3_d WHERE t3_d.PARENTID IN(SELECT t3_e.FOLDERID FROM t3 as t3_e WHERE t3_e.PARENTID='2f6161e879db43c1a5b82c21ddc49089' AND t3_e.FOLDERNAME = 'Level1') AND t3_d.FOLDERNAME = 'Level2') AND t3_c.FOLDERNAME = 'Level3') AND t3_b.FOLDERNAME = 'CopiedFolder') AND t3_a.FOLDERNAME = 'Movie Reviews') AND t2.DOCNAME = 'Last Discussion';
 
 drop table t1, t2, t3, t4;
 # End of 4.1 tests

mysql-test/main/subselect_mat.result

@@ -2404,6 +2404,21 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	32	test.t1.assignment_group	1	Using where; Using index
 2	MATERIALIZED	t2	ref	idx3,idx4	idx4	35	const	2	Using index condition; Using where
 2	MATERIALIZED	t3_i	eq_ref	PRIMARY	PRIMARY	32	test.t2.ugroup	1	Using index condition; Using where
+set statement optimizer_prune_level=1 for explain SELECT t1.assignment_group
+FROM t1, t3
+WHERE t1.assignment_group = t3.sys_id AND
+t1.dispatch_group IN
+(SELECT t2.ugroup
+FROM t2, t3 t3_i
+WHERE t2.ugroup = t3_i.sys_id AND 
+t3_i.type LIKE '59e22fb137032000158bbfc8bcbe5d52' AND
+t2.user = '86826bf03710200044e0bfc8bcbe5d79');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	2	
+1	PRIMARY	t1	ref	idx1,idx2	idx1	35	test.t2.ugroup	2	Using where
+1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	32	test.t1.assignment_group	1	Using where; Using index
+3	MATERIALIZED	t2	ref	idx3,idx4	idx4	35	const	2	Using index condition; Using where
+3	MATERIALIZED	t3_i	eq_ref	PRIMARY	PRIMARY	32	test.t2.ugroup	1	Using index condition; Using where
 SELECT t1.assignment_group
 FROM t1, t3
 WHERE t1.assignment_group = t3.sys_id AND

mysql-test/main/subselect_sj_mat.result

@@ -2446,6 +2446,21 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	32	test.t1.assignment_group	1	Using where; Using index
 2	MATERIALIZED	t2	ref	idx3,idx4	idx4	35	const	2	Using index condition; Using where
 2	MATERIALIZED	t3_i	eq_ref	PRIMARY	PRIMARY	32	test.t2.ugroup	1	Using index condition; Using where
+set statement optimizer_prune_level=1 for explain SELECT t1.assignment_group
+FROM t1, t3
+WHERE t1.assignment_group = t3.sys_id AND
+t1.dispatch_group IN
+(SELECT t2.ugroup
+FROM t2, t3 t3_i
+WHERE t2.ugroup = t3_i.sys_id AND 
+t3_i.type LIKE '59e22fb137032000158bbfc8bcbe5d52' AND
+t2.user = '86826bf03710200044e0bfc8bcbe5d79');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	2	
+1	PRIMARY	t1	ref	idx1,idx2	idx1	35	test.t2.ugroup	2	Using where
+1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	32	test.t1.assignment_group	1	Using where; Using index
+3	MATERIALIZED	t2	ref	idx3,idx4	idx4	35	const	2	Using index condition; Using where
+3	MATERIALIZED	t3_i	eq_ref	PRIMARY	PRIMARY	32	test.t2.ugroup	1	Using index condition; Using where
 SELECT t1.assignment_group
 FROM t1, t3
 WHERE t1.assignment_group = t3.sys_id AND

mysql-test/main/subselect_sj_mat.test

@@ -2163,6 +2163,7 @@ eval $q;
 
 set optimizer_switch='materialization=on';
 eval explain $q;
+eval set statement optimizer_prune_level=1 for explain $q;
 eval $q;
 
 DROP TABLE t1,t2,t3;

mysql-test/suite/sys_vars/r/optimizer_prune_level_basic.result

 SET @start_global_value = @@global.optimizer_prune_level;
 SELECT @start_global_value;
 @start_global_value
-1
+2
 SET @start_session_value = @@session.optimizer_prune_level;
 SELECT @start_session_value;
 @start_session_value
-1
+2
 '#--------------------FN_DYNVARS_115_01-------------------------#'
 SET @@global.optimizer_prune_level = 0;
 SET @@global.optimizer_prune_level = DEFAULT;
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
-1
+2
 SET @@session.optimizer_prune_level = 0;
 SET @@session.optimizer_prune_level = DEFAULT;
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
-1
+2
 '#--------------------FN_DYNVARS_115_02-------------------------#'
 SET @@global.optimizer_prune_level = DEFAULT;
-SELECT @@global.optimizer_prune_level = 1;
-@@global.optimizer_prune_level = 1
+SELECT @@global.optimizer_prune_level = 2;
+@@global.optimizer_prune_level = 2
 1
 SET @@session.optimizer_prune_level = DEFAULT;
-SELECT @@session.optimizer_prune_level = 1;
-@@session.optimizer_prune_level = 1
+SELECT @@session.optimizer_prune_level = 2;
+@@session.optimizer_prune_level = 2
 1
 '#--------------------FN_DYNVARS_115_03-------------------------#'
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
-1
+2
 SET @@global.optimizer_prune_level = 0;
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
@@ -38,6 +38,10 @@ SET @@global.optimizer_prune_level = 1;
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
 1
+SET @@global.optimizer_prune_level = 2;
+SELECT @@global.optimizer_prune_level;
+@@global.optimizer_prune_level
+2
 SET @@global.optimizer_prune_level = TRUE;
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
@@ -49,7 +53,7 @@ SELECT @@global.optimizer_prune_level;
 '#--------------------FN_DYNVARS_115_04-------------------------#'
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
-1
+2
 SET @@session.optimizer_prune_level = 0;
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
@@ -58,6 +62,10 @@ SET @@session.optimizer_prune_level = 1;
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
 1
+SET @@session.optimizer_prune_level = 2;
+SELECT @@session.optimizer_prune_level;
+@@session.optimizer_prune_level
+2
 SET @@session.optimizer_prune_level = TRUE;
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
@@ -69,7 +77,7 @@ SELECT @@session.optimizer_prune_level;
 '#------------------FN_DYNVARS_115_05-----------------------#'
 SET @@global.optimizer_prune_level = ON;
 ERROR 42000: Incorrect argument type to variable 'optimizer_prune_level'
-'Bug# 34840: Since it is a boolean variable, it should not give errors on 'ON' & 'OFF' values';
+'Bug# 34840: Since it is not a boolean variable, it should give errors on 'ON' & 'OFF' values';
 SET @@global.optimizer_prune_level = OFF;
 ERROR 42000: Incorrect argument type to variable 'optimizer_prune_level'
 SET @@global.optimizer_prune_level = 'ONN';
@@ -86,10 +94,16 @@ Warning	1292	Truncated incorrect optimizer_prune_level value: '-1024'
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
 0
-'Bug# 34840: Since it is a boolean variable, it should give errors on numeric values';
+'Bug# 34840: Since it is not a boolean variable, it should no give errors on numeric values';
 SET @@global.optimizer_prune_level = 65536;
 Warnings:
 Warning	1292	Truncated incorrect optimizer_prune_level value: '65536'
+SET @@global.optimizer_prune_level = 3;
+Warnings:
+Warning	1292	Truncated incorrect optimizer_prune_level value: '3'
+select @@global.optimizer_prune_level;
+@@global.optimizer_prune_level
+2
 SET @@global.optimizer_prune_level = 65530.34;
 ERROR 42000: Incorrect argument type to variable 'optimizer_prune_level'
 SET @@global.optimizer_prune_level = test;
@@ -121,7 +135,7 @@ Warnings:
 Warning	1292	Truncated incorrect optimizer_prune_level value: '65550'
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
-1
+2
 SET @@session.optimizer_prune_level = test;
 ERROR 42000: Incorrect argument type to variable 'optimizer_prune_level'
 '#------------------FN_DYNVARS_115_06-----------------------#'
@@ -164,8 +178,8 @@ ERROR 42S22: Unknown column 'optimizer_prune_level' in 'field list'
 SET @@global.optimizer_prune_level = @start_global_value;
 SELECT @@global.optimizer_prune_level;
 @@global.optimizer_prune_level
-1
+2
 SET @@session.optimizer_prune_level = @start_session_value;
 SELECT @@session.optimizer_prune_level;
 @@session.optimizer_prune_level
-1
+2

mysql-test/suite/sys_vars/r/sysvars_server_embedded.result

@@ -2265,9 +2265,9 @@ COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OPTIMIZER_PRUNE_LEVEL
 VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	BIGINT UNSIGNED
-VARIABLE_COMMENT	Controls the heuristic(s) applied during query optimization to prune less-promising partial plans from the optimizer search space. Meaning: 0 - do not apply any heuristic, thus perform exhaustive search; 1 - prune plans based on number of retrieved rows
+VARIABLE_COMMENT	Controls the heuristic(s) applied during query optimization to prune less-promising partial plans from the optimizer search space. Meaning: 0 - do not apply any heuristic, thus perform exhaustive search: 1 - prune plans based on cost and number of retrieved rows eq_ref: 2 - prune also if we find an eq_ref chain
 NUMERIC_MIN_VALUE	0
-NUMERIC_MAX_VALUE	1
+NUMERIC_MAX_VALUE	2
 NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -2435,9 +2435,9 @@ COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OPTIMIZER_PRUNE_LEVEL
 VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	BIGINT UNSIGNED
-VARIABLE_COMMENT	Controls the heuristic(s) applied during query optimization to prune less-promising partial plans from the optimizer search space. Meaning: 0 - do not apply any heuristic, thus perform exhaustive search; 1 - prune plans based on number of retrieved rows
+VARIABLE_COMMENT	Controls the heuristic(s) applied during query optimization to prune less-promising partial plans from the optimizer search space. Meaning: 0 - do not apply any heuristic, thus perform exhaustive search: 1 - prune plans based on cost and number of retrieved rows eq_ref: 2 - prune also if we find an eq_ref chain
 NUMERIC_MIN_VALUE	0
-NUMERIC_MAX_VALUE	1
+NUMERIC_MAX_VALUE	2
 NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO

mysql-test/suite/sys_vars/t/optimizer_prune_level_basic.test

@@ -60,10 +60,10 @@ SELECT @@session.optimizer_prune_level;
 ###########################################################
 
 SET @@global.optimizer_prune_level = DEFAULT;
-SELECT @@global.optimizer_prune_level = 1;
+SELECT @@global.optimizer_prune_level = 2;
 
 SET @@session.optimizer_prune_level = DEFAULT;
-SELECT @@session.optimizer_prune_level = 1;
+SELECT @@session.optimizer_prune_level = 2;
 
 
 --echo '#--------------------FN_DYNVARS_115_03-------------------------#'
@@ -77,6 +77,8 @@ SET @@global.optimizer_prune_level = 0;
 SELECT @@global.optimizer_prune_level;
 SET @@global.optimizer_prune_level = 1;
 SELECT @@global.optimizer_prune_level;
+SET @@global.optimizer_prune_level = 2;
+SELECT @@global.optimizer_prune_level;
 SET @@global.optimizer_prune_level = TRUE;
 SELECT @@global.optimizer_prune_level;
 SET @@global.optimizer_prune_level = FALSE;
@@ -94,6 +96,8 @@ SET @@session.optimizer_prune_level = 0;
 SELECT @@session.optimizer_prune_level;
 SET @@session.optimizer_prune_level = 1;
 SELECT @@session.optimizer_prune_level;
+SET @@session.optimizer_prune_level = 2;
+SELECT @@session.optimizer_prune_level;
 SET @@session.optimizer_prune_level = TRUE;
 SELECT @@session.optimizer_prune_level;
 SET @@session.optimizer_prune_level = FALSE;
@@ -107,7 +111,7 @@ SELECT @@session.optimizer_prune_level;
 
 --Error ER_WRONG_TYPE_FOR_VAR
 SET @@global.optimizer_prune_level = ON;
---echo 'Bug# 34840: Since it is a boolean variable, it should not give errors on 'ON' & 'OFF' values';
+--echo 'Bug# 34840: Since it is not a boolean variable, it should give errors on 'ON' & 'OFF' values';
 --Error ER_WRONG_TYPE_FOR_VAR
 SET @@global.optimizer_prune_level = OFF;
 --Error ER_WRONG_TYPE_FOR_VAR
@@ -122,9 +126,11 @@ SET @@global.optimizer_prune_level = FELSE;
 SET @@global.optimizer_prune_level = -1024;
 SELECT @@global.optimizer_prune_level;
 
---echo 'Bug# 34840: Since it is a boolean variable, it should give errors on numeric values';
+--echo 'Bug# 34840: Since it is not a boolean variable, it should no give errors on numeric values';
 
 SET @@global.optimizer_prune_level = 65536;
+SET @@global.optimizer_prune_level = 3;
+select @@global.optimizer_prune_level;
 --Error ER_WRONG_TYPE_FOR_VAR
 SET @@global.optimizer_prune_level = 65530.34;
 --Error ER_WRONG_TYPE_FOR_VAR

sql/my_json_writer.cc

@@ -159,10 +159,8 @@ Json_writer& Json_writer::add_member(const char *name, size_t len)
     auto is_uniq_key= emplaced.second;
     if(!is_uniq_key)
     {
-#ifdef QQQ
       sql_print_error("Duplicated key: %s\n", emplaced.first->c_str());
       VALIDITY_ASSERT(is_uniq_key);
-#endif /* QQQ */
     }
   }
 #endif

sql/opt_split.cc

@@ -769,7 +769,7 @@ void JOIN::add_keyuses_for_splitting()
     added_keyuse->validity_ref= &keyuse_ext->validity_var;
   }
 
-  if (sort_and_filter_keyuse(thd, &keyuse, true))
+  if (sort_and_filter_keyuse(this, &keyuse, true))
     goto err;
   optimize_keyuse(this, &keyuse);
 

sql/sql_select.h

@@ -1261,6 +1261,8 @@ class JOIN :public Sql_alloc
   table_map outer_join;
   /* Bitmap of tables used in the select list items */
   table_map select_list_used_tables;
+  /* Tables that have a possiblity to use EQ_ref */
+  table_map eq_ref_tables;
 
   table_map allowed_top_level_tables;
   ha_rows  send_records,found_records,join_examined_rows, accepted_rows;
@@ -2432,7 +2434,7 @@ void fix_list_after_tbl_changes(SELECT_LEX *new_parent, List<TABLE_LIST> *tlist)
 double get_tmp_table_lookup_cost(THD *thd, double row_count, uint row_size);
 double get_tmp_table_write_cost(THD *thd, double row_count, uint row_size);
 void optimize_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse_array);
-bool sort_and_filter_keyuse(THD *thd, DYNAMIC_ARRAY *keyuse,
+bool sort_and_filter_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse,
                             bool skip_unprefixed_keyparts);
 
 struct st_cond_statistic

sql/sys_vars.cc

@@ -2736,9 +2736,10 @@ static Sys_var_ulong Sys_optimizer_prune_level(
        "Controls the heuristic(s) applied during query optimization to prune "
        "less-promising partial plans from the optimizer search space. "
        "Meaning: 0 - do not apply any heuristic, thus perform exhaustive "
-       "search; 1 - prune plans based on number of retrieved rows",
+       "search: 1 - prune plans based on cost and number of retrieved rows "
+       "eq_ref: 2 - prune also if we find an eq_ref chain",
        SESSION_VAR(optimizer_prune_level), CMD_LINE(REQUIRED_ARG),
-       VALID_RANGE(0, 1), DEFAULT(1), BLOCK_SIZE(1));
+       VALID_RANGE(0, 2), DEFAULT(2), BLOCK_SIZE(1));
 
 static Sys_var_ulong Sys_optimizer_selectivity_sampling_limit(
        "optimizer_selectivity_sampling_limit",