From b34bb81eaf0f1fd653f93257fbbdaa4c31ea8ea5 Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Mon, 15 Mar 2021 22:48:30 -0700
Subject: [PATCH] MDEV-25112 MIN/MAX aggregation over an indexed column may
 return wrong result

If a query with implicit grouping contains in MIN/MAX set function in the
select list over a column that is a part of an index then the query
might be subject to MIN/MAX optimization. With this optimization the
server performs a look-up into an index, fetches a value of the column C
used in the MIN/MAX function and substitute the MIN/MAX expression for this
value. This allows to eliminate the table containing C from further join
processing. In order the optimization to be applied the WHERE condition
must be a conjunction of simple equality/inequality predicates or/and
BETWEEN predicates.
The bug fixed in the patch resulted in fetching a wrong value from the
index used for MIN/MAX optimization. It may happened when a BETWEEN
predicate containing the MIN/MAX value followed a strict inequality.

Approved by dmitry.shulga@mariadb.com
---
 mysql-test/r/func_group.result | 34 ++++++++++++++++++++++++++++++++++
 mysql-test/t/func_group.test   | 28 ++++++++++++++++++++++++++++
 sql/opt_sum.cc                 |  3 +++
 3 files changed, 65 insertions(+)

diff --git a/mysql-test/r/func_group.result b/mysql-test/r/func_group.result
index 0f9fdefb81a96..fb07ba76fb25c 100644
--- a/mysql-test/r/func_group.result
+++ b/mysql-test/r/func_group.result
@@ -2458,3 +2458,37 @@ select count(*)+sleep(0) from t1;
 count(*)+sleep(0)
 2
 drop table t1;
+#
+# MDEV-25112: MIN/MAX optimization for query containing BETWEEN in WHERE
+#
+create table t1 (a int) engine=myisam;
+insert into t1 values (267), (273),  (287), (303), (308);
+select max(a) from t1 where a < 303 and (a between 267 AND 287);
+max(a)
+287
+explain select max(a) from t1 where a < 303 and (a between 267 AND 287);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+select min(a) from t1 where a > 267 and (a between 273 AND 303);
+min(a)
+273
+explain select min(a) from t1 where a > 267 and (a between 273 AND 303);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+create index idx on t1(a);
+select max(a) from t1 where a < 303 and (a between 267 AND 287);
+max(a)
+287
+explain select max(a) from t1 where a < 303 and (a between 267 AND 287);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+select min(a) from t1 where a > 267 and (a between 273 AND 303);
+min(a)
+273
+explain select min(a) from t1 where a > 267 and (a between 273 AND 303);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+drop table t1;
+#
+# End of 10.2 tests
+#
diff --git a/mysql-test/t/func_group.test b/mysql-test/t/func_group.test
index 8bbc9e6a040f9..d7da9fe8c9679 100644
--- a/mysql-test/t/func_group.test
+++ b/mysql-test/t/func_group.test
@@ -1703,4 +1703,32 @@ select count(*)+sleep(0) from t1;
 
 drop table t1;
  
+--echo #
+--echo # MDEV-25112: MIN/MAX optimization for query containing BETWEEN in WHERE
+--echo #
+
+create table t1 (a int) engine=myisam;
+insert into t1 values (267), (273),  (287), (303), (308);
+
+let $q1=
+select max(a) from t1 where a < 303 and (a between 267 AND 287);
+let $q2=
+select min(a) from t1 where a > 267 and (a between 273 AND 303);
+
+eval $q1;
+eval explain $q1;
+eval $q2;
+eval explain $q2;
+
+create index idx on t1(a);
 
+eval $q1;
+eval explain $q1;
+eval $q2;
+eval explain $q2;
+
+drop table t1;
+
+--echo #
+--echo # End of 10.2 tests
+--echo #
diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc
index 02b95dae44a32..868d8b26f4bb1 100644
--- a/sql/opt_sum.cc
+++ b/sql/opt_sum.cc
@@ -830,7 +830,10 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo,
     if (is_field_part)
     {
       if (between || eq_type)
+      {
         *range_fl&= ~(NO_MAX_RANGE | NO_MIN_RANGE);
+        *range_fl&= ~(max_fl ? NEAR_MAX : NEAR_MIN);
+      }
       else
       {
         *range_fl&= ~(max_fl ? NO_MAX_RANGE : NO_MIN_RANGE);