MDEV-23634: Select query hanged the server and leads to OOM ...

Handle "col<>const" in the same way that MDEV-21958 did for
"col NOT IN(const-list)": do not use the condition for range/index_merge
accesses if there is a unique UNIQUE KEY(col).

The testcase is in main/range.test. The rest of test updates are
due to widespread use of 'pk<>1' in the testsuite. Changed the test
to use different but equivalent forms of the conditions.

mysql-test/include/icp_tests.inc

@@ -484,11 +484,11 @@ CREATE TABLE t1 (
 
 INSERT INTO t1 VALUES (1,9),(2,7),(3,6),(4,3),(5,1);
 
-EXPLAIN SELECT pk, c1 FROM t1 WHERE pk <> 3;
+EXPLAIN SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 
 SET SESSION optimizer_switch='index_condition_pushdown=off';
 
-SELECT pk, c1 FROM t1 WHERE pk <> 3;
+SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 
 DROP TABLE t1;
 
@@ -727,16 +727,16 @@ INSERT INTO t2 VALUES
 
 SET SESSION optimizer_switch='index_condition_pushdown=off';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0 
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
   HAVING t1.c != 5 ORDER BY t1.c;
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
   HAVING t1.c != 5 ORDER BY t1.c;
 
 SET SESSION optimizer_switch='index_condition_pushdown=on';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
   HAVING t1.c != 5 ORDER BY t1.c;
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
   HAVING t1.c != 5 ORDER BY t1.c;
 
 DROP TABLE t1,t2;

mysql-test/main/func_group.result

@@ -606,7 +606,7 @@ select min(a1) from t1 where a1 > 'KKK' or a1 < 'XXX';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	PRIMARY	PRIMARY	3	NULL	15	Using where; Using index
 explain 
-select min(a1) from t1 where a1 != 'KKK';
+select min(a1) from t1 where (a1 < 'KKK' or a1 > 'KKK');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	PRIMARY	PRIMARY	3	NULL	15	Using where; Using index
 explain

mysql-test/main/func_group.test

@@ -359,7 +359,7 @@ select min(t1.a1), min(t2.a4) from t1,t2 where t1.a1 < 'KKK' and t2.a4 < 'KKK';
 explain 
 select min(a1) from t1 where a1 > 'KKK' or a1 < 'XXX';
 explain 
-select min(a1) from t1 where a1 != 'KKK';
+select min(a1) from t1 where (a1 < 'KKK' or a1 > 'KKK');
 explain
 select max(a3) from t1 where a2 < 2 and a3 < 'SEA';
 explain

mysql-test/main/group_min_max.result

@@ -2940,7 +2940,7 @@ NULL
 EXPLAIN
 SELECT MIN( a ) FROM t1 WHERE a <> NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-x	x	x	x	x	x	x	x	x	Impossible WHERE noticed after reading const tables
+x	x	x	x	x	x	x	x	x	Using where; Using index
 SELECT MIN( a ) FROM t1 WHERE a <> NULL;
 MIN( a )
 NULL

mysql-test/main/index_merge_myisam.result

@@ -1687,7 +1687,8 @@ INSERT INTO t1 VALUES
 ALTER TABLE t1 ENABLE KEYS;
 EXPLAIN
 SELECT  * FROM t1 FORCE KEY (PRIMARY , i , c1 , c2) 
-WHERE pk = 255 OR i = 22 OR (pk  IN (1 , 136) AND c2  IN ('c' , 'w') AND (c1 NOT BETWEEN 'e' AND 'i' OR  c2 > 'g'))  OR pk != 1  ;
+WHERE pk = 255 OR i = 22 OR (pk  IN (1 , 136) AND c2  IN ('c' , 'w') AND (c1
+NOT BETWEEN 'e' AND 'i' OR  c2 > 'g'))  OR (pk is not null and (pk <1 or pk>1))  ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index_merge	PRIMARY,c1,i,c2	PRIMARY,i	0,5	NULL	69	Using sort_union(PRIMARY,i); Using where
 DROP TABLE t1;

mysql-test/main/index_merge_myisam.test

@@ -236,9 +236,11 @@ INSERT INTO t1 VALUES
 
 ALTER TABLE t1 ENABLE KEYS;
 
+# note: (pk is not null and (pk <1 or pk>1)) below is a sargable form of pk!=1
 EXPLAIN
 SELECT  * FROM t1 FORCE KEY (PRIMARY , i , c1 , c2) 
-WHERE pk = 255 OR i = 22 OR (pk  IN (1 , 136) AND c2  IN ('c' , 'w') AND (c1 NOT BETWEEN 'e' AND 'i' OR  c2 > 'g'))  OR pk != 1  ;
+WHERE pk = 255 OR i = 22 OR (pk  IN (1 , 136) AND c2  IN ('c' , 'w') AND (c1
+NOT BETWEEN 'e' AND 'i' OR  c2 > 'g'))  OR (pk is not null and (pk <1 or pk>1))  ;
 
 DROP TABLE t1;
 

mysql-test/main/innodb_icp.result

@@ -455,11 +455,11 @@ c1 INT NOT NULL,
 PRIMARY KEY (pk)
 );
 INSERT INTO t1 VALUES (1,9),(2,7),(3,6),(4,3),(5,1);
-EXPLAIN SELECT pk, c1 FROM t1 WHERE pk <> 3;
+EXPLAIN SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY	PRIMARY	4	NULL	4	Using where
 SET SESSION optimizer_switch='index_condition_pushdown=off';
-SELECT pk, c1 FROM t1 WHERE pk <> 3;
+SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 pk	c1
 1	9
 2	7
@@ -687,23 +687,23 @@ INSERT INTO t2 VALUES
 ('Ill'), ('eckqzsflbzaffti'), ('w'), ('she'), ('gxbwypqtjzwywwer'), ('w');
 SET SESSION optimizer_switch='index_condition_pushdown=off';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0 
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY	PRIMARY	4	NULL	1	Using where; Using filesort
 1	SIMPLE	t2	ref	a	a	515	test.t1.a	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4
 SET SESSION optimizer_switch='index_condition_pushdown=on';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY	PRIMARY	4	NULL	1	Using where; Using filesort
 1	SIMPLE	t2	ref	a	a	515	test.t1.a	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4

mysql-test/main/myisam_icp.result

@@ -448,11 +448,11 @@ c1 INT NOT NULL,
 PRIMARY KEY (pk)
 );
 INSERT INTO t1 VALUES (1,9),(2,7),(3,6),(4,3),(5,1);
-EXPLAIN SELECT pk, c1 FROM t1 WHERE pk <> 3;
+EXPLAIN SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	5	Using where
 SET SESSION optimizer_switch='index_condition_pushdown=off';
-SELECT pk, c1 FROM t1 WHERE pk <> 3;
+SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 pk	c1
 1	9
 2	7
@@ -680,23 +680,23 @@ INSERT INTO t2 VALUES
 ('Ill'), ('eckqzsflbzaffti'), ('w'), ('she'), ('gxbwypqtjzwywwer'), ('w');
 SET SESSION optimizer_switch='index_condition_pushdown=off';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0 
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	system	PRIMARY	NULL	NULL	NULL	1	
 1	SIMPLE	t2	ref	a	a	515	const	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4
 SET SESSION optimizer_switch='index_condition_pushdown=on';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	system	PRIMARY	NULL	NULL	NULL	1	
 1	SIMPLE	t2	ref	a	a	515	const	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4

mysql-test/main/range.result

@@ -3244,6 +3244,17 @@ SELECT * FROM t1 JOIN t2 ON (t2.code = t1.b) WHERE t1.a NOT IN ('baz', 'qux') OR
 id	a	b	code	num
 DROP TABLE t1, t2;
 #
+# MDEV-23634: Select query hanged the server and leads to OOM ...
+# (The fix is to add the same handling for "col!=const" as MDEV-21958 did for NOT IN)
+#
+create table t1 (pk int primary key, a int);
+insert into t1 (pk) values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+# must not use range:
+explain select * from t1 force index (primary) where pk != 1 and pk!=2 ;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	10	Using where
+drop table t1;
+#
 # MDEV-22251: get_key_scans_params: Conditional jump or move depends on uninitialised value
 #
 create table t1 (pk int, i int, v int, primary key (pk), key(v));

mysql-test/main/range.test

@@ -2215,6 +2215,17 @@ SELECT * FROM t1 JOIN t2 ON (t2.code = t1.b) WHERE t1.a NOT IN ('baz', 'qux') OR
 DROP TABLE t1, t2;
 
 
+--echo #
+--echo # MDEV-23634: Select query hanged the server and leads to OOM ...
+--echo # (The fix is to add the same handling for "col!=const" as MDEV-21958 did for NOT IN)
+--echo #
+create table t1 (pk int primary key, a int);
+insert into t1 (pk) values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+--echo # must not use range:
+explain select * from t1 force index (primary) where pk != 1 and pk!=2 ;
+drop table t1;
+
 --echo #
 --echo # MDEV-22251: get_key_scans_params: Conditional jump or move depends on uninitialised value
 --echo #

mysql-test/main/range_mrr_icp.result

@@ -3241,6 +3241,17 @@ SELECT * FROM t1 JOIN t2 ON (t2.code = t1.b) WHERE t1.a NOT IN ('baz', 'qux') OR
 id	a	b	code	num
 DROP TABLE t1, t2;
 #
+# MDEV-23634: Select query hanged the server and leads to OOM ...
+# (The fix is to add the same handling for "col!=const" as MDEV-21958 did for NOT IN)
+#
+create table t1 (pk int primary key, a int);
+insert into t1 (pk) values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+# must not use range:
+explain select * from t1 force index (primary) where pk != 1 and pk!=2 ;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	10	Using where
+drop table t1;
+#
 # MDEV-22251: get_key_scans_params: Conditional jump or move depends on uninitialised value
 #
 create table t1 (pk int, i int, v int, primary key (pk), key(v));

mysql-test/main/range_vs_index_merge.result

@@ -1810,11 +1810,11 @@ CREATE TABLE t1 (a int PRIMARY KEY, b int, INDEX idx(b));
 INSERT INTO t1 VALUES (167,9999), (168,10000);
 EXPLAIN
 SELECT * FROM t1
-WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY,idx	PRIMARY	0	NULL	2	Using index condition; Using where
 SELECT * FROM t1
-WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 a	b
 167	9999
 168	10000
@@ -1846,12 +1846,12 @@ test.t1	analyze	status	Engine-independent statistics collected
 test.t1	analyze	status	OK
 EXPLAIN
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9) 
 OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	state,capital	state	71	NULL	8	Using index condition; Using where
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9)
 OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 id	state	capital
 4	Florida	Tallahassee

mysql-test/main/range_vs_index_merge.test

@@ -1231,9 +1231,9 @@ INSERT INTO t1 VALUES (167,9999), (168,10000);
 
 EXPLAIN
 SELECT * FROM t1
-  WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+  WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 SELECT * FROM t1
-  WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+  WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 
 DROP TABLE t1;
 
@@ -1266,10 +1266,10 @@ ANALYZE TABLE t1;
  
 EXPLAIN
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9) 
    OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9)
    OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 
 DROP TABLE t1;

mysql-test/main/range_vs_index_merge_innodb.result

@@ -1816,11 +1816,11 @@ CREATE TABLE t1 (a int PRIMARY KEY, b int, INDEX idx(b));
 INSERT INTO t1 VALUES (167,9999), (168,10000);
 EXPLAIN
 SELECT * FROM t1
-WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	PRIMARY,idx	idx	5	NULL	2	Using where; Using index
 SELECT * FROM t1
-WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR a!=2;
+WHERE a BETWEEN 4 AND 5 AND b IN (255,4) OR a IN (2,14,25) OR (a<2 or a>2);
 a	b
 167	9999
 168	10000
@@ -1852,12 +1852,12 @@ test.t1	analyze	status	Engine-independent statistics collected
 test.t1	analyze	status	OK
 EXPLAIN
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9) 
 OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	state,capital	state	71	NULL	8	Using index condition; Using where
 SELECT * FROM t1 FORCE KEY (state,capital) 
-WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND id != 9 
+WHERE ( state = 'Alabama' OR state >= 'Colorado' ) AND (id<9 or id>9)
 OR ( capital >= 'Topeka' OR state = 'Kansas' ) AND state != 'Texas';
 id	state	capital
 4	Florida	Tallahassee

mysql-test/main/subselect_mat_cost_bugs.result

@@ -189,8 +189,8 @@ SELECT alias2.f2 AS field1
 FROM t1 AS alias1 JOIN ( SELECT * FROM t2 ) AS alias2 ON alias2.f3 = alias1.f1
 WHERE (
 SELECT t2.f2
-FROM t2 JOIN t1 ON t1.f1
-WHERE t1.f1 AND alias2.f10
+FROM t2 JOIN t1 ON (t1.f1>0 or t1.f1<0)
+WHERE (t1.f1>0 or t1.f1<0) AND alias2.f10
 )
 ORDER BY field1 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -203,8 +203,8 @@ SELECT alias2.f2 AS field1
 FROM t1 AS alias1 JOIN ( SELECT * FROM t2 ) AS alias2 ON alias2.f3 = alias1.f1
 WHERE (
 SELECT t2.f2
-FROM t2 JOIN t1 ON t1.f1
-WHERE t1.f1 AND alias2.f10
+FROM t2 JOIN t1 ON (t1.f1>0 or t1.f1<0)
+WHERE (t1.f1>0 or t1.f1<0) AND alias2.f10
 )
 ORDER BY field1 ;
 field1

mysql-test/main/subselect_mat_cost_bugs.test

@@ -217,8 +217,8 @@ SELECT alias2.f2 AS field1
 FROM t1 AS alias1 JOIN ( SELECT * FROM t2 ) AS alias2 ON alias2.f3 = alias1.f1
 WHERE (
         SELECT t2.f2
-        FROM t2 JOIN t1 ON t1.f1
-        WHERE t1.f1 AND alias2.f10
+        FROM t2 JOIN t1 ON (t1.f1>0 or t1.f1<0)
+        WHERE (t1.f1>0 or t1.f1<0) AND alias2.f10
 )
 ORDER BY field1 ;
 
@@ -226,8 +226,8 @@ SELECT alias2.f2 AS field1
 FROM t1 AS alias1 JOIN ( SELECT * FROM t2 ) AS alias2 ON alias2.f3 = alias1.f1
 WHERE (
         SELECT t2.f2
-        FROM t2 JOIN t1 ON t1.f1
-        WHERE t1.f1 AND alias2.f10
+        FROM t2 JOIN t1 ON (t1.f1>0 or t1.f1<0)
+        WHERE (t1.f1>0 or t1.f1<0) AND alias2.f10
 )
 ORDER BY field1 ;
 

mysql-test/suite/maria/icp.result

@@ -450,11 +450,11 @@ c1 INT NOT NULL,
 PRIMARY KEY (pk)
 );
 INSERT INTO t1 VALUES (1,9),(2,7),(3,6),(4,3),(5,1);
-EXPLAIN SELECT pk, c1 FROM t1 WHERE pk <> 3;
+EXPLAIN SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	5	Using where
 SET SESSION optimizer_switch='index_condition_pushdown=off';
-SELECT pk, c1 FROM t1 WHERE pk <> 3;
+SELECT pk, c1 FROM t1 WHERE (pk<3 or pk>3);
 pk	c1
 1	9
 2	7
@@ -682,23 +682,23 @@ INSERT INTO t2 VALUES
 ('Ill'), ('eckqzsflbzaffti'), ('w'), ('she'), ('gxbwypqtjzwywwer'), ('w');
 SET SESSION optimizer_switch='index_condition_pushdown=off';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0 
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	system	PRIMARY	NULL	NULL	NULL	1	
 1	SIMPLE	t2	ref	a	a	515	const	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4
 SET SESSION optimizer_switch='index_condition_pushdown=on';
 EXPLAIN
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	system	PRIMARY	NULL	NULL	NULL	1	
 1	SIMPLE	t2	ref	a	a	515	const	1	Using where
-SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND t1.b != 0
+SELECT t1.b, t1.c FROM t1, t2 WHERE t1.a = t2.a AND (t1.b<0 OR t1.b>0)
 HAVING t1.c != 5 ORDER BY t1.c;
 b	c
 1	4

mysql-test/suite/optimizer_unfixed_bugs/r/bug42991.result

@@ -245,7 +245,7 @@ UNLOCK TABLES;
 /*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
 /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
 /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
-select * from `table5` where  (col2 <= '6566-06-15' AND col24 <> 'd')  group by `col83` order by `col83` desc  ;
+select * from `table5` where  (col2 <= '6566-06-15' AND (col24 < 'd' or col24 > 'd'))  group by `col83` order by `col83` desc  ;
 col0	col1	col2	col3	col4	col5	col6	col7	col8	col9	col10	col11	col12	col13	col14	col15	col16	col17	col18	col19	col20	col21	col22	col23	col24	col25	col26	col27	col28	col29	col30	col31	col32	col33	col34	col35	col36	col37	col38	col39	col40	col41	col42	col43	col44	col45	col46	col47	col48	col49	col50	col51	col52	col53	col54	col55	col56	col57	col58	col59	col60	col61	col62	col63	col64	col65	col66	col67	col68	col69	col70	col71	col72	col73	col74	col75	col76	col77	col78	col79	col80	col81	col82	col83	col84	col85	col86	col87	col88	col89	col90	col91	col92	col93	col94	col95	col96	col97	col98	col99	col100	col101	col102	col103	col104	col105	col106	col107	col108	col109	col110	col111	col112	col113	col114	col115	col116	col117	col118	col119	col120	col121	col122	col123	col124	col125	col126	col127	col128	col129	col130	col131	col132	col133	col134	col135	col136	col137	col138	col139	col140	col141	col142	col143	col144	col145	col146	col147	col148	col149	col150	col151	col152	col153	col154	col155	col156	col157	col158	col159	col160	col161	col162	col163	col164	col165	col166	col167	col168	col169	col170	col171	col172	col173	col174	col175
 Warnings:
 Warning	1292	Truncated incorrect DOUBLE value: 'd'

mysql-test/suite/optimizer_unfixed_bugs/t/bug42991.test

@@ -242,9 +242,9 @@ UNLOCK TABLES;
 /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
 
 
-#explain select * from `table5` where  (col2 <= '6566-06-15' AND col24 <> 'd')  group by `col83` order by `col83` desc  ;
+#explain select * from `table5` where  (col2 <= '6566-06-15' AND (col24 < 'd' or col24 > 'd')  group by `col83` order by `col83` desc  ;
 
-select * from `table5` where  (col2 <= '6566-06-15' AND col24 <> 'd')  group by `col83` order by `col83` desc  ;
+select * from `table5` where  (col2 <= '6566-06-15' AND (col24 < 'd' or col24 > 'd'))  group by `col83` order by `col83` desc  ;
 
 drop table `table5`;
 SET debug_dbug= @saved_dbug;

sql/item_cmpfunc.h

@@ -832,11 +832,7 @@ class Item_func_ne :public Item_bool_rowready_func2
 {
 protected:
   SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param,
-                             Field *field, Item *value)
-  {
-    DBUG_ENTER("Item_func_ne::get_func_mm_tree");
-    DBUG_RETURN(get_ne_mm_tree(param, field, value, value));
-  }
+                             Field *field, Item *value);
 public:
   Item_func_ne(THD *thd, Item *a, Item *b):
     Item_bool_rowready_func2(thd, a, b) {}

sql/opt_range.cc

@@ -449,6 +449,7 @@ void print_range_for_non_indexed_field(String *out, Field *field,
 static void print_min_range_operator(String *out, const ha_rkey_function flag);
 static void print_max_range_operator(String *out, const ha_rkey_function flag);
 
+static bool is_field_an_unique_index(RANGE_OPT_PARAM *param, Field *field);
 
 /*
   SEL_IMERGE is a list of possible ways to do index merge, i.e. it is
@@ -7689,6 +7690,21 @@ SEL_TREE *Item_bool_func::get_ne_mm_tree(RANGE_OPT_PARAM *param,
 }
 
 
+SEL_TREE *Item_func_ne::get_func_mm_tree(RANGE_OPT_PARAM *param,
+                                         Field *field, Item *value)
+{
+  DBUG_ENTER("Item_func_ne::get_func_mm_tree");
+  /*
+    If this condition is a "col1<>...", where there is a UNIQUE KEY(col1),
+    do not construct a SEL_TREE from it. A condition that excludes just one
+    row in the table is not selective (unless there are only a few rows)
+  */
+  if (is_field_an_unique_index(param, field))
+    DBUG_RETURN(NULL);
+  DBUG_RETURN(get_ne_mm_tree(param, field, value, value));
+}
+
+
 SEL_TREE *Item_func_between::get_func_mm_tree(RANGE_OPT_PARAM *param,
                                               Field *field, Item *value)
 {
@@ -7787,28 +7803,16 @@ SEL_TREE *Item_func_in::get_func_mm_tree(RANGE_OPT_PARAM *param,
         DBUG_RETURN(0);
 
       /*
-        If this is "unique_key NOT IN (...)", do not consider it sargable (for
-        any index, not just the unique one). The logic is as follows:
+        if this is a "col1 NOT IN (...)", and there is a UNIQUE KEY(col1), do
+        not constuct a SEL_TREE from it. The rationale is as follows:
          - if there are only a few constants, this condition is not selective
            (unless the table is also very small in which case we won't gain
            anything)
-         - If there are a lot of constants, the overhead of building and
+         - if there are a lot of constants, the overhead of building and
            processing enormous range list is not worth it.
       */
-      if (param->using_real_indexes)
-      {
-        key_map::Iterator it(field->key_start);
-        uint key_no;
-        while ((key_no= it++) != key_map::Iterator::BITMAP_END)
-        {
-          KEY *key_info= &field->table->key_info[key_no];
-          if (key_info->user_defined_key_parts == 1 &&
-              (key_info->flags & HA_NOSAME))
-          {
-            DBUG_RETURN(0);
-          }
-        }
-      }
+      if (is_field_an_unique_index(param, field))
+        DBUG_RETURN(0);
 
       /* Get a SEL_TREE for "(-inf|NULL) < X < c_0" interval.  */
       uint i=0;
@@ -8526,6 +8530,38 @@ SEL_TREE *Item_equal::get_mm_tree(RANGE_OPT_PARAM *param, Item **cond_ptr)
 }
 
 
+/*
+  @brief
+    Check if there is an one-segment unique key that matches the field exactly
+
+  @detail
+    In the future we could also add "almost unique" indexes where any value is
+    present only in a few rows (but necessarily exactly one row)
+*/
+static bool is_field_an_unique_index(RANGE_OPT_PARAM *param, Field *field)
+{
+  DBUG_ENTER("is_field_an_unique_index");
+
+  // The check for using_real_indexes is there because of the heuristics
+  // this function is used for.
+  if (param->using_real_indexes)
+  {
+    key_map::Iterator it(field->key_start);
+    uint key_no;
+    while ((key_no= it++) != key_map::Iterator::BITMAP_END)
+    {
+      KEY *key_info= &field->table->key_info[key_no];
+      if (key_info->user_defined_key_parts == 1 &&
+          (key_info->flags & HA_NOSAME))
+      {
+        DBUG_RETURN(true);
+      }
+    }
+  }
+  DBUG_RETURN(false);
+}
+
+
 SEL_TREE *
 Item_bool_func::get_mm_parts(RANGE_OPT_PARAM *param, Field *field,
 	                     Item_func::Functype type, Item *value)