MDEV-8989: ORDER BY optimizer ignores equality propagation

Post-fix #2:
- Update test results
- Make the optimization conditional under @@optimizer_switch flag.
- The optimization is now disabled by default, so .result files
  are changed back to be what they were before the MDEV-8989 patch.

mysql-test/r/compress.result

@@ -607,7 +607,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

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

@@ -580,7 +580,7 @@ The following options may be given as the first argument:
  semijoin_with_cache, join_cache_incremental, 
  join_cache_hashed, join_cache_bka, 
  optimize_join_buffer_size, table_elimination, 
- extended_keys, exists_to_in
+ extended_keys, exists_to_in, orderby_uses_equalities
  --optimizer-use-condition-selectivity=# 
  Controls selectivity of which conditions the optimizer
  takes into account to calculate cardinality of a partial

mysql-test/r/named_pipe.result

@@ -601,7 +601,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/order_by.result

@@ -2990,6 +2990,8 @@ drop table t1,t2;
 #
 # MDEV-8989: ORDER BY optimizer ignores equality propagation
 #
+set @tmp_8989=@@optimizer_switch;
+set optimizer_switch='orderby_uses_equalities=on';
 create table t0(a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 create table t1(a int);
@@ -3128,3 +3130,5 @@ explain select * from t3 where b=a order by b limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	index	NULL	a	5	NULL	10	Using where
 drop table t0,t1,t2,t3;
+set @@optimizer_switch=@tmp_8989;
+set optimizer_switch='orderby_uses_equalities=on';

mysql-test/r/pool_of_threads.result

@@ -603,7 +603,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/select.result

@@ -606,7 +606,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/select_pkeycache.result

@@ -606,7 +606,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/shm.result

@@ -601,7 +601,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/ssl.result

@@ -610,7 +610,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/ssl_compress.result

@@ -607,7 +607,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.fld1	1	Using where; Using index
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using filesort
+1	SIMPLE	t1	ALL	period	NULL	NULL	NULL	41810	Using temporary; Using filesort
 1	SIMPLE	t3	ref	period	period	4	test.t1.period	4181	
 explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

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

@@ -2642,17 +2642,17 @@ ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OPTIMIZER_SWITCH
-SESSION_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on
-GLOBAL_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on
+SESSION_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=off
+GLOBAL_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=off
 GLOBAL_VALUE_ORIGIN	COMPILE-TIME
-DEFAULT_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on
+DEFAULT_VALUE	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=off,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=off
 VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	FLAGSET
 VARIABLE_COMMENT	Fine-tune the optimizer behavior
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	index_merge,index_merge_union,index_merge_sort_union,index_merge_intersection,index_merge_sort_intersection,engine_condition_pushdown,index_condition_pushdown,derived_merge,derived_with_keys,firstmatch,loosescan,materialization,in_to_exists,semijoin,partial_match_rowid_merge,partial_match_table_scan,subquery_cache,mrr,mrr_cost_based,mrr_sort_keys,outer_join_with_cache,semijoin_with_cache,join_cache_incremental,join_cache_hashed,join_cache_bka,optimize_join_buffer_size,table_elimination,extended_keys,exists_to_in,default
+ENUM_VALUE_LIST	index_merge,index_merge_union,index_merge_sort_union,index_merge_intersection,index_merge_sort_intersection,engine_condition_pushdown,index_condition_pushdown,derived_merge,derived_with_keys,firstmatch,loosescan,materialization,in_to_exists,semijoin,partial_match_rowid_merge,partial_match_table_scan,subquery_cache,mrr,mrr_cost_based,mrr_sort_keys,outer_join_with_cache,semijoin_with_cache,join_cache_incremental,join_cache_hashed,join_cache_bka,optimize_join_buffer_size,table_elimination,extended_keys,exists_to_in,orderby_uses_equalities,default
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OPTIMIZER_USE_CONDITION_SELECTIVITY

mysql-test/t/order_by.test

@@ -2000,6 +2000,8 @@ drop table t1,t2;
 --echo #
 --echo # MDEV-8989: ORDER BY optimizer ignores equality propagation
 --echo #
+set @tmp_8989=@@optimizer_switch;
+set optimizer_switch='orderby_uses_equalities=on';
 create table t0(a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 
@@ -2075,3 +2077,7 @@ explain select * from t3 where b=a order by a limit 10;
 explain select * from t3 where b=a order by b limit 10;
 drop table t0,t1,t2,t3;
 
+set @@optimizer_switch=@tmp_8989;
+
+set optimizer_switch='orderby_uses_equalities=on';
+

sql/sql_priv.h

@@ -224,7 +224,7 @@
 #define OPTIMIZER_SWITCH_TABLE_ELIMINATION         (1ULL << 26)
 #define OPTIMIZER_SWITCH_EXTENDED_KEYS             (1ULL << 27)
 #define OPTIMIZER_SWITCH_EXISTS_TO_IN              (1ULL << 28)
-#define OPTIMIZER_SWITCH_USE_CONDITION_SELECTIVITY (1ULL << 29)
+#define OPTIMIZER_SWITCH_ORDERBY_EQ_PROP           (1ULL << 29)
 
 #define OPTIMIZER_SWITCH_DEFAULT   (OPTIMIZER_SWITCH_INDEX_MERGE | \
                                     OPTIMIZER_SWITCH_INDEX_MERGE_UNION | \

sql/sql_select.cc

@@ -12333,7 +12333,8 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
             can be used without tmp. table.
           */
           bool can_subst_to_first_table= false;
-          if (first_is_base_table &&
+          if (optimizer_flag(join->thd, OPTIMIZER_SWITCH_ORDERBY_EQ_PROP) &&
+              first_is_base_table &&
               order->item[0]->real_item()->type() == Item::FIELD_ITEM &&
               join->cond_equal)
           {
@@ -20748,6 +20749,9 @@ void compute_part_of_sort_key_for_equals(JOIN *join, TABLE *table,
 {
   col_keys->clear_all();
   col_keys->merge(item_field->field->part_of_sortkey);
+  
+  if (!optimizer_flag(join->thd, OPTIMIZER_SWITCH_ORDERBY_EQ_PROP))
+    return;
 
   Item_equal *item_eq= NULL;
 

sql/sys_vars.cc

@@ -2391,7 +2391,9 @@ export const char *optimizer_switch_names[]=
   "table_elimination",
   "extended_keys",
   "exists_to_in",
-  "default", NullS
+  "orderby_uses_equalities",
+  "default", 
+  NullS
 };
 static bool fix_optimizer_switch(sys_var *self, THD *thd,
                                  enum_var_type type)