Assertion `ptr == a || ptr == b' failed in Field_bit::cmp upon query with GROUP_CONCAT

SET group_concat_max_len= 1024;

CREATE TABLE t1 ( 

    a TINYINT(44) ZEROFILL,

    b BIT(15),

    c BINARY(229)

);

CREATE VIEW v1 AS SELECT * FROM t1;

INSERT INTO t1 VALUES

    (1,b'0','a'),(2,b'0','b'),(3,b'1','c'),(4,b'1','d'),

    (5,b'1','e'),(6,b'1','f'),(7,b'1','g'),(8,b'0','h');

INSERT INTO t1 SELECT a.* FROM t1 a, t1 b, t1 c, t1 d;

SELECT GROUP_CONCAT(c,b,a ORDER BY 3,2,1) AS f FROM v1;

# Cleanup

DROP VIEW v1;

DROP TABLE t1;

mysqld: /data/src/10.1/sql/field.h:3387: virtual int Field_bit::cmp(const uchar*, const uchar*): Assertion `ptr == a || ptr == b' failed.

190508 15:22:54 [ERROR] mysqld got signal 6 ;

#7  0x00007fbe1f6acf12 in __GI___assert_fail (assertion=0x55e350e9cac0 "ptr == a || ptr == b", file=0x55e350e9c8df "/data/src/10.1/sql/field.h", line=3387, function=0x55e350ea1a00 <Field_bit::cmp(unsigned char const*, unsigned char const*)::__PRETTY_FUNCTION__> "virtual int Field_bit::cmp(const uchar*, const uchar*)") at assert.c:101

#8  0x000055e350684acb in Field_bit::cmp (this=0x7fbe16903d20, a=0x7fbe16ad6195 "", b=0x7fbe16acb615 "") at /data/src/10.1/sql/field.h:3387

#9  0x000055e35074cc06 in group_concat_key_cmp_with_order (arg=0x7fbe16845788, key1=0x7fbe16ad60a8, key2=0x7fbe16acb528) at /data/src/10.1/sql/item_sum.cc:2992

#10 0x000055e350cf80bc in tree_insert (tree=0x7fbe210d45f0, key=0x7fbe16acb528, key_size=0, custom_arg=0x7fbe16845788) at /data/src/10.1/mysys/tree.c:210

#11 0x000055e35074dc4d in copy_to_tree (key=0x7fbe16acb528, count=1, arg=0x7fbe210d45f0) at /data/src/10.1/sql/item_sum.cc:3324

#12 0x000055e350cf8f76 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16acb508, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:551

#13 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16acac88, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#14 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16ac9b88, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#15 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16ac7988, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#16 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16ac5788, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#17 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16ac1388, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#18 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16abce48, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#19 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16ab4648, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#20 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16aabe48, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#21 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16a9ad08, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#22 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16a89bc8, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#23 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16bf3a88, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#24 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16bd1888, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#25 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16b8d448, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#26 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16a5e088, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#27 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16a5e198, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#28 0x000055e350cf8f27 in tree_walk_left_root_right (tree=0x7fbe168458d8, element=0x7fbe16a5e3b8, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0) at /data/src/10.1/mysys/tree.c:550

#29 0x000055e350cf8ebe in tree_walk (tree=0x7fbe168458d8, action=0x55e35074db86 <copy_to_tree(void*, element_count, void*)>, argument=0x7fbe210d45f0, visit=left_root_right) at /data/src/10.1/mysys/tree.c:538

#30 0x000055e35074dd80 in Item_func_group_concat::repack_tree (this=0x7fbe16845788, thd=0x7fbe187d0070) at /data/src/10.1/sql/item_sum.cc:3342

#31 0x000055e35074e1ac in Item_func_group_concat::add (this=0x7fbe16845788) at /data/src/10.1/sql/item_sum.cc:3410

#32 0x000055e35074fa0d in Aggregator_simple::add (this=0x7fbe168faab8) at /data/src/10.1/sql/item_sum.h:672

#33 0x000055e3504cf20b in Item_sum::aggregator_add (this=0x7fbe16845788) at /data/src/10.1/sql/item_sum.h:521

#34 0x000055e3504c5894 in update_sum_func (func_ptr=0x7fbe1684a048) at /data/src/10.1/sql/sql_select.cc:23534

#35 0x000055e3504bc829 in end_send_group (join=0x7fbe16848a20, join_tab=0x7fbe1684ada0, end_of_records=false) at /data/src/10.1/sql/sql_select.cc:19824

#36 0x000055e3504b9ba0 in evaluate_join_record (join=0x7fbe16848a20, join_tab=0x7fbe1684aa58, error=0) at /data/src/10.1/sql/sql_select.cc:18702

#37 0x000055e3504b9641 in sub_select (join=0x7fbe16848a20, join_tab=0x7fbe1684aa58, end_of_records=false) at /data/src/10.1/sql/sql_select.cc:18518

#38 0x000055e3504b8ce9 in do_select (join=0x7fbe16848a20, fields=0x7fbe16848e20, table=0x0, procedure=0x0) at /data/src/10.1/sql/sql_select.cc:18134

#39 0x000055e350493a18 in JOIN::exec_inner (this=0x7fbe16848a20) at /data/src/10.1/sql/sql_select.cc:3275

#40 0x000055e350490cab in JOIN::exec (this=0x7fbe16848a20) at /data/src/10.1/sql/sql_select.cc:2562

#41 0x000055e350494239 in mysql_select (thd=0x7fbe187d0070, rref_pointer_array=0x7fbe187d4560, tables=0x7fbe16845c90, wild_num=0, fields=..., conds=0x0, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=2147748608, result=0x7fbe16848a00, unit=0x7fbe187d3bb8, select_lex=0x7fbe187d42b8) at /data/src/10.1/sql/sql_select.cc:3499

#42 0x000055e350489923 in handle_select (thd=0x7fbe187d0070, lex=0x7fbe187d3af0, result=0x7fbe16848a00, setup_tables_done_option=0) at /data/src/10.1/sql/sql_select.cc:376

#43 0x000055e3504590f2 in execute_sqlcom_select (thd=0x7fbe187d0070, all_tables=0x7fbe16845c90) at /data/src/10.1/sql/sql_parse.cc:5951

#44 0x000055e35044f453 in mysql_execute_command (thd=0x7fbe187d0070) at /data/src/10.1/sql/sql_parse.cc:3038

#45 0x000055e35045cd6b in mysql_parse (thd=0x7fbe187d0070, rawbuf=0x7fbe16845088 "SELECT GROUP_CONCAT(c,b,a ORDER BY 3,2,1) AS f FROM v1", length=54, parser_state=0x7fbe210d61e0) at /data/src/10.1/sql/sql_parse.cc:7469

#46 0x000055e35044b465 in dispatch_command (command=COM_QUERY, thd=0x7fbe187d0070, packet=0x7fbe1a7f0071 "", packet_length=54) at /data/src/10.1/sql/sql_parse.cc:1499

#47 0x000055e35044a223 in do_command (thd=0x7fbe187d0070) at /data/src/10.1/sql/sql_parse.cc:1131

#48 0x000055e350585745 in do_handle_one_connection (thd_arg=0x7fbe187d0070) at /data/src/10.1/sql/sql_connect.cc:1330

#49 0x000055e35058548b in handle_one_connection (arg=0x7fbe187d0070) at /data/src/10.1/sql/sql_connect.cc:1242

#50 0x000055e3509b8a8c in pfs_spawn_thread (arg=0x7fbe1ec39c70) at /data/src/10.1/storage/perfschema/pfs.cc:1861

#51 0x00007fbe20d534a4 in start_thread (arg=0x7fbe210d7700) at pthread_create.c:456

#52 0x00007fbe1f769d0f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

commit 979cad229148ba8d28d94c1ca621bacd11847b66

Author: Sergei Golubchik

Date:   Wed Jun 21 16:07:54 2017 +0200

    MDEV-9531 GROUP_CONCAT with ORDER BY inside takes a lot of memory while it's executed

    group concat tree is allocated in a memroot, so the only way to free

    memory is to copy a part of the tree into a new memroot.

    track the accumilated length of the result, and when it crosses

    the threshold  - copy the result into a new tree, free the old one.