[#MDEV-20423] Assertion `0' failed or `btr_validate_index(index, 0, false)' in row_upd_sec_index_entry or error code 126: Index is corrupted upon DELETE with TIME_ROUND

This crash is very similar to ~~MDEV-18156~~, but now with TIME_ROUND_FRACTIONAL instead of PAD_CHAR_TO_FULL_LENGTH.
It should be addressed in a separate patch after the fix for ~~MDEV-18156~~ propagates to 10.4.

This crash is also very similar to ~~MDEV-18153~~, but the generation expressions are different:

SET sql_mode='';

CREATE OR REPLACE TABLE t1 (

  a DATETIME(6),

  v VARCHAR(30) GENERATED ALWAYS AS (CAST(a AS DATETIME(3))) VIRTUAL,

  KEY (v)

);

INSERT IGNORE INTO t1 (a) VALUES ('2001-01-01 10:20:30.999999');

SELECT * FROM t1;

SET sql_mode=TIME_ROUND_FRACTIONAL;

FLUSH TABLES;

SELECT * FROM t1;

UPDATE t1 SET a='2001-01-02 10:20:30.999999';

#0  0x00007ffff76f357f in raise () from /lib64/libc.so.6

#1  0x00007ffff76dd895 in abort () from /lib64/libc.so.6

#2  0x00007ffff76dd769 in __assert_fail_base.cold.0 () from /lib64/libc.so.6

#3  0x00007ffff76eba26 in __assert_fail () from /lib64/libc.so.6

#4  0x0000000000eff9ac in row_upd_sec_index_entry (node=0x7fff60083cd0, thr=0x7fff60083fd8)

    at /home/bar/maria-git/server.10.4/storage/innobase/row/row0upd.cc:2429

#5  0x0000000000f0001e in row_upd_sec_step (node=0x7fff60083cd0, thr=0x7fff60083fd8)

    at /home/bar/maria-git/server.10.4/storage/innobase/row/row0upd.cc:2543

#6  0x0000000000f02736 in row_upd (node=0x7fff60083cd0, thr=0x7fff60083fd8)

    at /home/bar/maria-git/server.10.4/storage/innobase/row/row0upd.cc:3319

#7  0x0000000000f02a9d in row_upd_step (thr=0x7fff60083fd8)

    at /home/bar/maria-git/server.10.4/storage/innobase/row/row0upd.cc:3434

#8  0x0000000000eb654c in row_update_for_mysql (prebuilt=0x7fff60083518)

    at /home/bar/maria-git/server.10.4/storage/innobase/row/row0mysql.cc:1889

#9  0x0000000000d60723 in ha_innobase::update_row (this=0x7fff6001dcf8,

    old_row=0x7fff6001d8a0 "\374\231g\202\245\036\017B?\027\062\060\060\061-01-01 10:20:31.000",

    new_row=0x7fff6001d870 "\374\231g\204\245\036\017B?\027\062\060\060\061-01-02 10:20:31.000")

    at /home/bar/maria-git/server.10.4/storage/innobase/handler/ha_innodb.cc:8840

#10 0x0000000000b4bc0a in handler::ha_update_row (this=0x7fff6001dcf8,

    old_data=0x7fff6001d8a0 "\374\231g\202\245\036\017B?\027\062\060\060\061-01-01 10:20:31.000",

    new_data=0x7fff6001d870 "\374\231g\204\245\036\017B?\027\062\060\060\061-01-02 10:20:31.000")

    at /home/bar/maria-git/server.10.4/sql/handler.cc:6727

#11 0x000000000091b9ad in mysql_update (thd=0x7fff60000d60, table_list=0x7fff60014270, fields=...,

    values=..., conds=0x0, order_num=0, order=0x0, limit=18446744073709551615, ignore=false,

    found_return=0x7ffff41d6218, updated_return=0x7ffff41d6210)

    at /home/bar/maria-git/server.10.4/sql/sql_update.cc:1045

#12 0x0000000000820bc2 in mysql_execute_command (thd=0x7fff60000d60)

    at /home/bar/maria-git/server.10.4/sql/sql_parse.cc:4369

#13 0x000000000082cd07 in mysql_parse (thd=0x7fff60000d60,

    rawbuf=0x7fff60014168 "UPDATE t1 SET a='2001-01-02 10:20:30.999999'", length=44,

    parser_state=0x7ffff41d7000, is_com_multi=false, is_next_command=false)

    at /home/bar/maria-git/server.10.4/sql/sql_parse.cc:7908

#14 0x000000000081981c in dispatch_command (command=COM_QUERY, thd=0x7fff60000d60,

    packet=0x7fff600085e1 "UPDATE t1 SET a='2001-01-02 10:20:30.999999'", packet_length=44,

    is_com_multi=false, is_next_command=false) at /home/bar/maria-git/server.10.4/sql/sql_parse.cc:1842

#15 0x0000000000817fc6 in do_command (thd=0x7fff60000d60)

SET sql_mode='';

CREATE OR REPLACE TABLE t1 (

  a TIME(6),

  v VARCHAR(30) GENERATED ALWAYS AS (CAST(a AS TIME(3))) VIRTUAL,

  KEY (v)

);

INSERT IGNORE INTO t1 (a) VALUES ('10:20:30.999999');

SELECT * FROM t1;

SET sql_mode=TIME_ROUND_FRACTIONAL;

FLUSH TABLES;

SELECT * FROM t1;

UPDATE t1 SET a='11:20:30.999999';

[MDEV-20423] Assertion `0' failed or `btr_validate_index(index, 0, false)' in row_upd_sec_index_entry or error code 126: Index is corrupted upon DELETE with TIME_ROUND_FRACTIONAL Created: 2019-08-26 Updated: 2019-09-18 Resolved: 2019-09-18
Status:	Closed
Project:	MariaDB Server
Component/s:	Data types, Virtual Columns
Affects Version/s:	10.4
Fix Version/s:	10.4.9, 10.5.0

[MDEV-20423] Assertion `0' failed or `btr_validate_index(index, 0, false)' in row_upd_sec_index_entry or error code 126: Index is corrupted upon DELETE with TIME_ROUND_FRACTIONAL Created: 2019-08-26 Updated: 2019-09-18 Resolved: 2019-09-18