12 files changed, 291 insertions, 45 deletions

diff --git a/mysql-test/main/join_outer_innodb.result b/mysql-test/main/join_outer_innodb.result
index ccd73ec955f..a0358094baa 100644
--- a/mysql-test/main/join_outer_innodb.result
+++ b/mysql-test/main/join_outer_innodb.result
@@ -434,46 +434,46 @@ where t1.a10 = 1;
 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	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	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	t13	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where; Using index
 1	SIMPLE	t2	ref	PRIMARY	PRIMARY	4	test.t1.a1	1	Using index
-1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where; Using index
 1	SIMPLE	m2	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where; Using index
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.b2	1	Using where; Using index
+1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
+1	SIMPLE	l3	eq_ref	PRIMARY	PRIMARY	4	test.m2.m2	1	Using where
+1	SIMPLE	t14	ALL	PRIMARY	NULL	NULL	NULL	4	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	4	test.t1.a2	1	Using index
-1	SIMPLE	t5	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
-1	SIMPLE	l3	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	1	
-1	SIMPLE	t6	eq_ref	PRIMARY	PRIMARY	4	test.t1.a3	1	Using where; Using index
-1	SIMPLE	t14	eq_ref	PRIMARY	PRIMARY	2	test.t1.a8	1	Using where
 1	SIMPLE	t15	eq_ref	PRIMARY	PRIMARY	2	test.t1.a9	1	Using where; Using index
 1	SIMPLE	t16	ref	PRIMARY	PRIMARY	2	test.t15.o1	1	Using where
 1	SIMPLE	t10	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
+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
 explain select * from v1;
 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	t8	eq_ref	PRIMARY	PRIMARY	1	test.t1.a4	1	Using index
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	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	t13	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where; Using index
 1	SIMPLE	t2	ref	PRIMARY	PRIMARY	4	test.t1.a1	1	Using index
-1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
 1	SIMPLE	l4	eq_ref	PRIMARY	PRIMARY	4	test.t13.m2	1	Using where; Using index
 1	SIMPLE	m2	ref	PRIMARY,m3	PRIMARY	4	test.t1.a1	1	Using where; Using index
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.b2	1	Using where; Using index
+1	SIMPLE	t9	ref	PRIMARY	PRIMARY	1	test.t1.a4	1	
+1	SIMPLE	l3	eq_ref	PRIMARY	PRIMARY	4	test.m2.m2	1	Using where
+1	SIMPLE	t14	ALL	PRIMARY	NULL	NULL	NULL	4	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	4	test.t1.a2	1	Using index
-1	SIMPLE	t5	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
-1	SIMPLE	l3	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (incremental, BNL join)
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	1	test.t1.a7	1	
-1	SIMPLE	t6	eq_ref	PRIMARY	PRIMARY	4	test.t1.a3	1	Using where; Using index
-1	SIMPLE	t14	eq_ref	PRIMARY	PRIMARY	2	test.t1.a8	1	Using where
 1	SIMPLE	t15	eq_ref	PRIMARY	PRIMARY	2	test.t1.a9	1	Using where; Using index
 1	SIMPLE	t16	ref	PRIMARY	PRIMARY	2	test.t15.o1	1	Using where
 1	SIMPLE	t10	ALL	PRIMARY	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
+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
 drop view v1;
 drop table t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13,t14,t15,t16;
 #
diff --git a/mysql-test/main/selectivity.result b/mysql-test/main/selectivity.result
index f11fee4b985..c548748b242 100644
--- a/mysql-test/main/selectivity.result
+++ b/mysql-test/main/selectivity.result
@@ -1753,5 +1753,62 @@ a
 1991
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 DROP TABLE t1;
+#
+# MDEV-20424: New default value for optimizer_use_condition-selectivity
+# leads to bad plan
+#
+create table t1(a int, b int, c int, d int, key(a,b));
+insert into t1 select 50,seq-1,seq-1,seq from seq_1_to_10;
+insert into t1 select seq-1,seq-1,seq-1,seq from seq_1_to_100 limit 90;
+create table t2(a int, b int, c int, primary key(a));
+insert into t2 select seq-1,seq-1,seq-1 from seq_1_to_100;
+create table t3(a int, b int, c int, primary key(a));
+insert into t3 select seq-1,seq-1,seq-1 from seq_1_to_100 limit 30;
+set optimizer_use_condition_selectivity=1;
+explain extended select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	10	NULL	9	100.00	Using index condition; Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.d	1	100.00	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.c	1	100.00	Using index
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t1`.`c` and `test`.`t3`.`a` = `test`.`t1`.`d` and `test`.`t1`.`a` = 50 and `test`.`t1`.`b` <= 100
+select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+b	a	a	b
+0	0	1	1
+1	1	2	2
+2	2	3	3
+3	3	4	4
+4	4	5	5
+5	5	6	6
+6	6	7	7
+7	7	8	8
+8	8	9	9
+9	9	10	10
+set optimizer_use_condition_selectivity=2;
+explain extended select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	10	NULL	9	9.00	Using index condition; Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.d	1	100.00	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.c	1	100.00	Using index
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t1`.`c` and `test`.`t3`.`a` = `test`.`t1`.`d` and `test`.`t1`.`a` = 50 and `test`.`t1`.`b` <= 100
+select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+b	a	a	b
+0	0	1	1
+1	1	2	2
+2	2	3	3
+3	3	4	4
+4	4	5	5
+5	5	6	6
+6	6	7	7
+7	7	8	8
+8	8	9	9
+9	9	10	10
+set optimizer_use_condition_selectivity= @@optimizer_use_condition_selectivity;
+drop table t1,t2,t3;
 # End of 10.1 tests
 set @@global.histogram_size=@save_histogram_size;
diff --git a/mysql-test/main/selectivity.test b/mysql-test/main/selectivity.test
index a9588ea205d..3cf4f320994 100644
--- a/mysql-test/main/selectivity.test
+++ b/mysql-test/main/selectivity.test
@@ -1206,6 +1206,35 @@ set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivit
 
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-20424: New default value for optimizer_use_condition-selectivity
+--echo # leads to bad plan
+--echo #
+
+create table t1(a int, b int, c int, d int, key(a,b));
+insert into t1 select 50,seq-1,seq-1,seq from seq_1_to_10;
+insert into t1 select seq-1,seq-1,seq-1,seq from seq_1_to_100 limit 90;
+
+create table t2(a int, b int, c int, primary key(a));
+insert into t2 select seq-1,seq-1,seq-1 from seq_1_to_100;
+
+create table t3(a int, b int, c int, primary key(a));
+insert into t3 select seq-1,seq-1,seq-1 from seq_1_to_100 limit 30;
+
+let $query= select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+
+set optimizer_use_condition_selectivity=1;
+eval explain extended $query;
+eval $query;
+
+set optimizer_use_condition_selectivity=2;
+eval explain extended $query;
+eval $query;
+set optimizer_use_condition_selectivity= @@optimizer_use_condition_selectivity;
+
+drop table t1,t2,t3;
+
 --echo # End of 10.1 tests
 
 #
diff --git a/mysql-test/main/selectivity_innodb.result b/mysql-test/main/selectivity_innodb.result
index 80295473e9b..b293f6adb5f 100644
--- a/mysql-test/main/selectivity_innodb.result
+++ b/mysql-test/main/selectivity_innodb.result
@@ -1763,6 +1763,63 @@ a
 1991
 set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 DROP TABLE t1;
+#
+# MDEV-20424: New default value for optimizer_use_condition-selectivity
+# leads to bad plan
+#
+create table t1(a int, b int, c int, d int, key(a,b));
+insert into t1 select 50,seq-1,seq-1,seq from seq_1_to_10;
+insert into t1 select seq-1,seq-1,seq-1,seq from seq_1_to_100 limit 90;
+create table t2(a int, b int, c int, primary key(a));
+insert into t2 select seq-1,seq-1,seq-1 from seq_1_to_100;
+create table t3(a int, b int, c int, primary key(a));
+insert into t3 select seq-1,seq-1,seq-1 from seq_1_to_100 limit 30;
+set optimizer_use_condition_selectivity=1;
+explain extended select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	10	NULL	11	100.00	Using index condition; Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.d	1	100.00	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.c	1	100.00	Using index
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t1`.`c` and `test`.`t3`.`a` = `test`.`t1`.`d` and `test`.`t1`.`a` = 50 and `test`.`t1`.`b` <= 100
+select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+b	a	a	b
+0	0	1	1
+1	1	2	2
+2	2	3	3
+3	3	4	4
+4	4	5	5
+5	5	6	6
+6	6	7	7
+7	7	8	8
+8	8	9	9
+9	9	10	10
+set optimizer_use_condition_selectivity=2;
+explain extended select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	10	NULL	11	11.00	Using index condition; Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.d	1	100.00	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.c	1	100.00	Using index
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t2`.`a` = `test`.`t1`.`c` and `test`.`t3`.`a` = `test`.`t1`.`d` and `test`.`t1`.`a` = 50 and `test`.`t1`.`b` <= 100
+select t1.b,t2.a,t3.a,t3.b from t1,t2,t3
+where t1.c = t2.a AND t1.d = t3.a and t1.a = 50 and t1.b <= 100;
+b	a	a	b
+0	0	1	1
+1	1	2	2
+2	2	3	3
+3	3	4	4
+4	4	5	5
+5	5	6	6
+6	6	7	7
+7	7	8	8
+8	8	9	9
+9	9	10	10
+set optimizer_use_condition_selectivity= @@optimizer_use_condition_selectivity;
+drop table t1,t2,t3;
 # End of 10.1 tests
 set @@global.histogram_size=@save_histogram_size;
 set optimizer_switch=@save_optimizer_switch_for_selectivity_test;
diff --git a/mysql-test/main/stat_tables.result b/mysql-test/main/stat_tables.result
index 35a21377689..3ff10cc2448 100644
--- a/mysql-test/main/stat_tables.result
+++ b/mysql-test/main/stat_tables.result
@@ -218,8 +218,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 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	
-1	SIMPLE	n1	ref	PRIMARY,i_n_regionkey	i_n_regionkey	5	dbt3_s001.region.r_regionkey	5	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
 select o_year,
 sum(case when nation = 'UNITED STATES' then volume else 0 end) /
 sum(volume) as mkt_share
diff --git a/mysql-test/suite/innodb/r/ibuf_not_empty.result b/mysql-test/suite/innodb/r/ibuf_not_empty.result
index 5147521b19f..dc852dfb8e5 100644
--- a/mysql-test/suite/innodb/r/ibuf_not_empty.result
+++ b/mysql-test/suite/innodb/r/ibuf_not_empty.result
@@ -21,6 +21,11 @@ INSERT INTO t1 SELECT 0,b,c FROM t1;
 # restart: --innodb-force-recovery=6 --innodb-change-buffer-dump
 check table t1;
 Table	Op	Msg_type	Msg_text
-test.t1	check	status	OK
+test.t1	check	Warning	InnoDB: Index 'b' contains #### entries, should be 4096.
+test.t1	check	error	Corrupt
+# restart
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+InnoDB		0 transactions not purged
+SET GLOBAL innodb_fast_shutdown=0;
 # restart
 DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/t/ibuf_not_empty.combinations b/mysql-test/suite/innodb/t/ibuf_not_empty.combinations
new file mode 100644
index 00000000000..729380593f3
--- /dev/null
+++ b/mysql-test/suite/innodb/t/ibuf_not_empty.combinations
@@ -0,0 +1,5 @@
+[strict_crc32]
+--innodb-checksum-algorithm=strict_crc32
+
+[strict_full_crc32]
+--innodb-checksum-algorithm=strict_full_crc32
diff --git a/mysql-test/suite/innodb/t/ibuf_not_empty.test b/mysql-test/suite/innodb/t/ibuf_not_empty.test
index 470d375c661..14d8728cdf8 100644
--- a/mysql-test/suite/innodb/t/ibuf_not_empty.test
+++ b/mysql-test/suite/innodb/t/ibuf_not_empty.test
@@ -42,9 +42,44 @@ INSERT INTO t1 SELECT 0,b,c FROM t1;
 INSERT INTO t1 SELECT 0,b,c FROM t1;
 INSERT INTO t1 SELECT 0,b,c FROM t1;
 INSERT INTO t1 SELECT 0,b,c FROM t1;
+let MYSQLD_DATADIR=`select @@datadir`;
+let PAGE_SIZE=`select @@innodb_page_size`;
+
+--source include/shutdown_mysqld.inc
+
+# Corrupt the change buffer bitmap, to claim that pages are clean
+perl;
+do "$ENV{MTR_SUITE_DIR}/include/crc32.pl";
+my $file = "$ENV{MYSQLD_DATADIR}/test/t1.ibd";
+open(FILE, "+<$file") || die "Unable to open $file";
+binmode FILE;
+my $ps= $ENV{PAGE_SIZE};
+my $page;
+die "Unable to read $file" unless sysread(FILE, $page, $ps) == $ps;
+my $full_crc32 = unpack("N",substr($page,54,4)) & 0x10; # FIL_SPACE_FLAGS
+die "Unable to read $file" unless sysread(FILE, $page, $ps) == $ps;
+# Clean the change buffer bitmap.
+substr($page,38,$ps - 38 - 8) = chr(0) x ($ps - 38 - 8);
+my $polynomial = 0x82f63b78; # CRC-32C
+if ($full_crc32)
+{
+    my $ck = mycrc32(substr($page, 0, $ps-4), 0, $polynomial);
+    substr($page, $ps-4, 4) = pack("N", $ck);
+}
+else
+{
+    my $ck= pack("N",mycrc32(substr($page, 4, 22), 0, $polynomial) ^
+                 mycrc32(substr($page, 38, $ps - 38 - 8), 0, $polynomial));
+    substr($page,0,4)=$ck;
+    substr($page,$ps-8,4)=$ck;
+}
+sysseek(FILE, $ps, 0) || die "Unable to rewind $file\n";
+syswrite(FILE, $page, $ps)==$ps || die "Unable to write $file\n";
+close(FILE) || die "Unable to close $file";
+EOF
 
 --let $restart_parameters= --innodb-force-recovery=6 --innodb-change-buffer-dump
---source include/restart_mysqld.inc
+--source include/start_mysqld.inc
 
 --replace_regex /contains \d+ entries/contains #### entries/
 check table t1;
@@ -52,5 +87,13 @@ check table t1;
 --let $restart_parameters=
 --source include/restart_mysqld.inc
 
+# Ensure that the slow shutdown will not time out due to running purge.
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+--source include/wait_all_purged.inc
+# The change buffer merge for the injected corruption must complete
+# without exceeding the 60-second shutdown_server timeout.
+SET GLOBAL innodb_fast_shutdown=0;
+--source include/restart_mysqld.inc
+
 # Cleanup
 DROP TABLE t1;
diff --git a/mysql-test/suite/innodb_fts/r/innodb_fts_misc.result b/mysql-test/suite/innodb_fts/r/innodb_fts_misc.result
index 0bcea9165b1..91f875377e2 100644
--- a/mysql-test/suite/innodb_fts/r/innodb_fts_misc.result
+++ b/mysql-test/suite/innodb_fts/r/innodb_fts_misc.result
@@ -1,4 +1,3 @@
-drop table if exists t1;
 CREATE TABLE t1 (
 id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
 a VARCHAR(200),
@@ -409,7 +408,6 @@ AGAINST ('"following database"@10' IN BOOLEAN MODE);
 id
 105
 DROP TABLE t1;
-drop table if exists t50;
 set names utf8;
 "----------Test1---------"
 create table t50 (s1 varchar(60) character set utf8 collate utf8_bin) engine = innodb;
@@ -648,9 +646,6 @@ s1
 ŁŁŁŁ
 LLLL
 ŁŁŁŁ ŁŁŁŁ
-DROP TABLE if EXISTS t2;
-Warnings:
-Note	1051	Unknown table 'test.t2'
 CREATE TABLE t2 (s1 VARCHAR(60) CHARACTER SET UTF8 COLLATE UTF8_POLISH_CI) ENGINE = InnoDB;
 CREATE FULLTEXT INDEX i ON t2 ( s1);
 INSERT INTO t2 VALUES
@@ -702,9 +697,14 @@ DROP TABLE t1;
 CREATE TABLE t1 (id INT,char_column VARCHAR(60));
 CREATE TABLE t2 (FTS_DOC_ID BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, a TEXT)ENGINE=InnoDB;
 ALTER TABLE t2 DROP a;
-SET @@autocommit=0;
 CREATE FULLTEXT INDEX i ON t1 (char_column);
 INSERT INTO t1 values (1,'aaa');
+CREATE TABLE mdev20987_1(f1 INT NOT NULL, PRIMARY KEY(f1))ENGINE=InnoDB;
+CREATE TABLE mdev20987_2(f1 INT NOT NULL, f2 CHAR(100),
+FULLTEXT(f2),
+FOREIGN KEY(f1) REFERENCES mdev20987_1(f1))ENGINE=InnoDB;
+INSERT INTO mdev20987_1 VALUES(1);
+INSERT INTO mdev20987_2 VALUES(1, 'mariadb');
 # restart
 SHOW CREATE TABLE t2;
 Table	Create Table
@@ -713,12 +713,8 @@ t2	CREATE TABLE `t2` (
   PRIMARY KEY (`FTS_DOC_ID`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DELETE FROM t1 WHERE MATCH(char_column) AGAINST ('bbb');
-SET @@autocommit=1;
-DROP TABLE t1, t2;
+DROP TABLE t1, t2, mdev20987_2, mdev20987_1;
 "----------Test28---------"
-drop table if exists `fts_test`;
-Warnings:
-Note	1051	Unknown table 'test.fts_test'
 create table `fts_test`(`a` text,fulltext key(`a`))engine=innodb;
 set session autocommit=0;
 insert into `fts_test` values ('');
@@ -908,9 +904,6 @@ id	title	body
 2	How To Use MySQL Well	After you went through a ...
 3	Optimizing MySQL	In this tutorial we will show ...
 DROP TABLE articles;
-drop table if exists t1;
-Warnings:
-Note	1051	Unknown table 'test.t1'
 create table t1 (FTS_DOC_ID bigint unsigned auto_increment not null primary key,
 title varchar(200),body text,fulltext(title,body)) engine=innodb;
 insert into t1 set body='test';
diff --git a/mysql-test/suite/innodb_fts/t/innodb_fts_misc.test b/mysql-test/suite/innodb_fts/t/innodb_fts_misc.test
index 4563d6dde77..e1f4874a1d4 100644
--- a/mysql-test/suite/innodb_fts/t/innodb_fts_misc.test
+++ b/mysql-test/suite/innodb_fts/t/innodb_fts_misc.test
@@ -7,10 +7,6 @@
 let collation=UTF8_UNICODE_CI;
 --source include/have_collation.inc
 
---disable_warnings
-drop table if exists t1;
---enable_warnings
-
 # Create FTS table
 CREATE TABLE t1 (
         id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
@@ -403,10 +399,6 @@ DROP TABLE t1;
 #------------------------------------------------------------------------------
 # More FTS test from peter's testing
 #------------------------------------------------------------------------------
---disable_warnings
-drop table if exists t50;
---enable_warnings
-
 set names utf8;
 
 
@@ -608,7 +600,6 @@ CREATE FULLTEXT INDEX i ON t1 (s1);
 INSERT INTO t1 VALUES
 ('a'),('b'),('c'),('d'),('ŁŁŁŁ'),('LLLL'),(NULL),('ŁŁŁŁ ŁŁŁŁ'),('LLLLLLLL');
 SELECT * FROM t1 WHERE MATCH(s1) AGAINST ('LLLL' COLLATE UTF8_UNICODE_520_CI);
-DROP TABLE if EXISTS t2;
 CREATE TABLE t2 (s1 VARCHAR(60) CHARACTER SET UTF8 COLLATE UTF8_POLISH_CI) ENGINE = InnoDB;
 CREATE FULLTEXT INDEX i ON t2 ( s1);
 INSERT INTO t2 VALUES
@@ -672,17 +663,21 @@ DROP TABLE t1;
 CREATE TABLE t1 (id INT,char_column VARCHAR(60));
 CREATE TABLE t2 (FTS_DOC_ID BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, a TEXT)ENGINE=InnoDB;
 ALTER TABLE t2 DROP a;
-SET @@autocommit=0;
 CREATE FULLTEXT INDEX i ON t1 (char_column);
 INSERT INTO t1 values (1,'aaa');
+
+CREATE TABLE mdev20987_1(f1 INT NOT NULL, PRIMARY KEY(f1))ENGINE=InnoDB;
+CREATE TABLE mdev20987_2(f1 INT NOT NULL, f2 CHAR(100),
+                FULLTEXT(f2),
+                FOREIGN KEY(f1) REFERENCES mdev20987_1(f1))ENGINE=InnoDB;
+INSERT INTO mdev20987_1 VALUES(1);
+INSERT INTO mdev20987_2 VALUES(1, 'mariadb');
 --source include/restart_mysqld.inc
 SHOW CREATE TABLE t2;
 DELETE FROM t1 WHERE MATCH(char_column) AGAINST ('bbb');
-SET @@autocommit=1;
-DROP TABLE t1, t2;
+DROP TABLE t1, t2, mdev20987_2, mdev20987_1;
 
 --echo "----------Test28---------"
-drop table if exists `fts_test`;
 create table `fts_test`(`a` text,fulltext key(`a`))engine=innodb;
 set session autocommit=0;
 insert into `fts_test` values ('');
@@ -871,8 +866,6 @@ DROP TABLE articles;
 # Test for Bug 13940669 - 64901: INNODB: ASSERTION FAILURE IN
 # THREAD 34387022112 IN FILE REM0CMP.CC LINE 5
 
-drop table if exists t1;
-
 create table t1 (FTS_DOC_ID bigint unsigned auto_increment not null primary key,
 title varchar(200),body text,fulltext(title,body)) engine=innodb;
 
diff --git a/mysql-test/suite/perfschema/r/misc.result b/mysql-test/suite/perfschema/r/misc.result
index 4c8fdca8e68..2e4d21d625a 100644
--- a/mysql-test/suite/perfschema/r/misc.result
+++ b/mysql-test/suite/perfschema/r/misc.result
@@ -134,3 +134,19 @@ truncate performance_schema.events_statements_history	0
 select * from t1	3
 insert into t1 select RAND()*10000 from t1	6
 drop table t1;
+#
+# MDEV-17896 Assertion `pfs->get_refcount() > 0' failed
+# in release_table_share
+#
+SELECT COUNT(*)<@@performance_schema_max_table_instances FROM
+performance_schema.objects_summary_global_by_type WHERE OBJECT_TYPE='TABLE';
+COUNT(*)<@@performance_schema_max_table_instances
+1
+CREATE TABLE t0(a INT);
+SELECT * FROM t0;
+a
+DROP TEMPORARY TABLE IF EXISTS t0;
+Warnings:
+Note	1051	Unknown table 'test.t0'
+FLUSH TABLE t0;
+DROP TABLE t0;
diff --git a/mysql-test/suite/perfschema/t/misc.test b/mysql-test/suite/perfschema/t/misc.test
index c9f7dc6bfc0..80ce64f0302 100644
--- a/mysql-test/suite/perfschema/t/misc.test
+++ b/mysql-test/suite/perfschema/t/misc.test
@@ -222,3 +222,51 @@ insert into t1 select RAND()*10000 from t1;
 select sql_text, rows_examined from performance_schema.events_statements_history;
 drop table t1;
 
+--echo #
+--echo # MDEV-17896 Assertion `pfs->get_refcount() > 0' failed
+--echo # in release_table_share
+--echo #
+
+# There must be at least one available slot in PFS table_share_array for
+# this test to be meaningful. If there are no free slots we must
+# restart mysqld, it is the only way to reset PFS table_share_array
+let $query= SELECT COUNT(*)<@@performance_schema_max_table_instances FROM
+  performance_schema.objects_summary_global_by_type WHERE OBJECT_TYPE='TABLE';
+
+let $free_slots_available= `$query`;
+
+if (!$free_slots_available)
+{
+  source include/restart_mysqld.inc;
+}
+eval $query;
+
+CREATE TABLE t0(a INT);
+
+# TABLE_SHARE must be cached in the table definition cache.
+SELECT * FROM t0;
+
+# Dropping t0 using DROP TEMPORARY frees up a slot in table_share_array,
+# but the persistent table is not correctly dropped, i.e. TABLE_SHARE::m_psi
+# still points to that slot in table_share_array.
+DROP TEMPORARY TABLE IF EXISTS t0;
+
+# Try re-using each and every slot in PFS table_share_array. If bug is
+# there, we re-use t0 slot.
+# The newly created table that re-uses the t0 slot ends up
+# resetting the PFS_table_share refcount.
+let $i= `SELECT @@performance_schema_max_table_instances`;
+disable_query_log;
+while ($i)
+{
+  # Memory engine is here to reduce disk IO
+  eval CREATE TABLE t$i(a INT) ENGINE=MEMORY;
+  eval DROP TABLE t$i;
+  dec $i;
+}
+enable_query_log;
+
+# FLUSH TABLE crashes the server when PFS_table_share is found with
+# an unexpected refcount.
+FLUSH TABLE t0;
+DROP TABLE t0;