From d3c81804ba8754e3f920b266a917b7facbae23f9 Mon Sep 17 00:00:00 2001
From: Monty <monty@mariadb.org>
Date: Wed, 21 Jun 2023 14:00:18 +0300
Subject: [PATCH] MDEV-31494 Server crashes in ha_partition::index_blocks /
 get_key_scans_params

MDEV-31445 Server crashes in ha_partition::index_blocks / cost_for_index_read

The crash happened in the case where partition pruning finds 0
partitions.
---
 mysql-test/main/partition.result | 38 ++++++++++++++++++++++++++++++++
 mysql-test/main/partition.test   | 37 +++++++++++++++++++++++++++++++
 sql/ha_partition.cc              |  2 +-
 3 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/partition.result b/mysql-test/main/partition.result
index 78d4aa3f87c..9155f90d781 100644
--- a/mysql-test/main/partition.result
+++ b/mysql-test/main/partition.result
@@ -2858,3 +2858,41 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t3	ref_or_null	a1,b	a1	10	func,test.t2.a	198	Using where; Full scan on NULL key
 set optimizer_switch=@tmp_os;
 drop table t1,t2,t3;
+#
+# MDEV-31494 Server crashes in ha_partition::index_blocks /
+# get_key_scans_params
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+CREATE TABLE t2 (b INT, c INT, KEY(c)) PARTITION BY LIST (b) (PARTITION p0 VALUES IN (1,2), PARTITION p1 VALUES IN (3,4));
+INSERT INTO t2 VALUES (1,1),(2,2);
+explain SELECT * FROM t1 STRAIGHT_JOIN t2 WHERE t2.b = 5 AND t2.c = 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+SELECT * FROM t1 STRAIGHT_JOIN t2 WHERE t2.b = 5 AND t2.c = 10;
+a	b	c
+DROP TABLE t1, t2;
+#
+# MDEV-31445 Server crashes in ha_partition::index_blocks /
+# cost_for_index_read
+#
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT);
+CREATE TABLE t3 (c INT, d INT, KEY(d)) PARTITION BY KEY (c) PARTITIONS 2;
+CREATE TABLE t4 (e INT);
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1),(2);
+INSERT INTO t3 VALUES (1,1),(2,2);
+INSERT INTO t4 VALUES (1),(2);
+explain SELECT * FROM t1 LEFT JOIN (t2 JOIN t3 ON (0 IN (SELECT e FROM t4) AND t3.d = t2.b)) ON (t3.c < t2.b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	PRIMARY	t3	ref	d	d	5	test.t2.b	1	Using where
+2	SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT * FROM t1 LEFT JOIN (t2 JOIN t3 ON (0 IN (SELECT e FROM t4) AND t3.d = t2.b)) ON (t3.c < t2.b);
+a	b	c	d
+1	NULL	NULL	NULL
+2	NULL	NULL	NULL
+drop table t1,t2,t3,t4;
+# End of 11.0 tests
diff --git a/mysql-test/main/partition.test b/mysql-test/main/partition.test
index d96031a6b2b..101e696a9ff 100644
--- a/mysql-test/main/partition.test
+++ b/mysql-test/main/partition.test
@@ -3062,3 +3062,40 @@ set optimizer_switch=@tmp_os;
 
 drop table t1,t2,t3;
 
+
+--echo #
+--echo # MDEV-31494 Server crashes in ha_partition::index_blocks /
+--echo # get_key_scans_params
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+
+CREATE TABLE t2 (b INT, c INT, KEY(c)) PARTITION BY LIST (b) (PARTITION p0 VALUES IN (1,2), PARTITION p1 VALUES IN (3,4));
+
+INSERT INTO t2 VALUES (1,1),(2,2);
+explain SELECT * FROM t1 STRAIGHT_JOIN t2 WHERE t2.b = 5 AND t2.c = 10;
+SELECT * FROM t1 STRAIGHT_JOIN t2 WHERE t2.b = 5 AND t2.c = 10;
+DROP TABLE t1, t2;
+
+--echo #
+--echo # MDEV-31445 Server crashes in ha_partition::index_blocks /
+--echo # cost_for_index_read
+--echo #
+
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT);
+CREATE TABLE t3 (c INT, d INT, KEY(d)) PARTITION BY KEY (c) PARTITIONS 2;
+CREATE TABLE t4 (e INT);
+
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1),(2);
+INSERT INTO t3 VALUES (1,1),(2,2);
+INSERT INTO t4 VALUES (1),(2);
+
+explain SELECT * FROM t1 LEFT JOIN (t2 JOIN t3 ON (0 IN (SELECT e FROM t4) AND t3.d = t2.b)) ON (t3.c < t2.b);
+SELECT * FROM t1 LEFT JOIN (t2 JOIN t3 ON (0 IN (SELECT e FROM t4) AND t3.d = t2.b)) ON (t3.c < t2.b);
+
+drop table t1,t2,t3,t4;
+
+--echo # End of 11.0 tests
diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index a7cfbc44971..2a36436758b 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -12204,7 +12204,7 @@ ulonglong ha_partition::index_blocks(uint index, uint ranges, ha_rows rows)
   ulonglong blocks= 0;
   ulonglong active_partitions= bitmap_bits_set(&m_part_info->read_partitions);
   /* Assume rows are evenly dived among partitions */
-  rows= (rows+ active_partitions -1) / active_partitions;
+  rows= (rows+ active_partitions -1) / MY_MAX(active_partitions, 1);
 
   for (uint i= bitmap_get_first_set(&m_part_info->read_partitions);
        i < m_tot_parts;