[#MDEV-23398] OPTIMIZE causes strange errors and further data corruption with myisam_repair

-- source include/have_sequence.inc

CREATE TABLE t1 (id INT AUTO_INCREMENT PRIMARY KEY, a TEXT, b TEXT, KEY(id,a(64),b(64))) ENGINE=MyISAM;

INSERT INTO t1 (a) SELECT REPEAT('e',65173) FROM seq_1_to_50;

UPDATE t1 SET a = 'x';

SET SESSION myisam_repair_threads= 6, myisam_sort_buffer_size= 131072;

OPTIMIZE TABLE t1;

INSERT INTO t1 (a) VALUES (NULL);

# Cleanup

DROP TABLE t1;

10.2 dc716da4
OPTIMIZE TABLE t1;
Table Op Msg_type Msg_text
test.t1 optimize error myisam_sort_buffer_size is too small. Current myisam_sort_buffer_size: 65536 rows: 162961 sort_length: 144
test.t1 optimize error Found key at page -1 that points to record outside datafile
test.t1 optimize status Operation failed
INSERT INTO t1 (a) VALUES (NULL);
bug.corrupt1 [ fail ]
Test ended at 2020-08-04 15:35:47

CURRENT_TEST: bug.corrupt1
mysqltest: At line 8: query 'INSERT INTO t1 (a) VALUES (NULL)' failed: 144: Table './test/t1' is marked as crashed and last (automatic?) repair failed

Everything in OPTIMIZE output is strange: current myisam_sort_buffer_size is wrong, the number of rows has nothing to do with the table, and page -1 is obviously a problem. The warning in the error log isn't good either:

2020-08-04 15:35:46 140051098892032 [Warning] Warning: Optimize table got errno 0 on test.t1, retrying

And further the table is marked as crashed.

Reproducible on 10.1-10.5.

[MDEV-23398] OPTIMIZE causes strange errors and further data corruption with myisam_repair_threads and too small sort buffer Created: 2020-08-04 Updated: 2023-04-27
Status:	Open
Project:	MariaDB Server
Component/s:	Storage Engine - MyISAM
Affects Version/s:	10.1, 10.2, 10.3, 10.4, 10.5
Fix Version/s:	10.4, 10.5

[MDEV-23398] OPTIMIZE causes strange errors and further data corruption with myisam_repair_threads and too small sort buffer Created: 2020-08-04 Updated: 2023-04-27