InnoDB purge for index on virtual column is trying to access an incomplete record

diff --git a/mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test b/mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

index 1862de268af..5e2cf3fd59b 100644

--- a/mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

+++ b/mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

@@ -184,7 +184,8 @@ connection default;

 update t set a = repeat('m', 16000) where a like "aaa%";

 connect(lock_table, localhost, root);

 lock table t write;

-disconnect prevent_purge;

+connection prevent_purge;

+commit;

 connection default;

 --source ../../innodb/include/wait_all_purged.inc

 disconnect lock_table;

@@ -194,6 +195,28 @@ commit;

 set global debug_dbug=@old_dbug;

 drop table t;

+CREATE TABLE t1(

+ u INT PRIMARY KEY, b BLOB, ug INT GENERATED ALWAYS AS (u) VIRTUAL,

+ INDEX bug(b(100),ug)

+) ENGINE=InnoDB;

+INSERT INTO t1 (u,b) VALUES(1,REPEAT('a',16384));

+connection prevent_purge;

+start transaction with consistent snapshot;

+connection default;

+DELETE FROM t1;

+SET DEBUG_SYNC='blob_write_middle SIGNAL halfway WAIT_FOR purged';

+send INSERT INTO t1 (u,b) VALUES(1,REPEAT('a',16384));

+connection prevent_purge;

+SET DEBUG_SYNC='now WAIT_FOR halfway';

+COMMIT;

+--source ../../innodb/include/wait_all_purged.inc

+SET DEBUG_SYNC='now SIGNAL purged';

+disconnect prevent_purge;

+

+connection default;

+reap;

+DROP TABLE t1;

+

 --source include/wait_until_count_sessions.inc

 set debug_sync=reset;

 SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

Version: '10.2.13-MariaDB-debug-log'  socket: '/mariadb/10.2-ext/build/mysql-test/var/tmp/mysqld.1.sock'  port: 16000  Source distribution

mysqld: /mariadb/10.2-ext/storage/innobase/include/data0data.ic:429: dfield_t* dtuple_get_nth_field(const dtuple_t*, ulint): Assertion `tuple' failed.

…

mysys/stacktrace.c:267(my_print_stacktrace)[0x55a6a0877ec9]

include/data0data.ic:430(dtuple_get_nth_field(dtuple_t const*, unsigned long))[0x55a6a08784e3]

row/row0purge.cc:584(0purge.cc:477)[0x55a6a0878b49]

que/que0que.cc:1055(que_thr_step(que_thr_t*))[0x55a6a0758888]

que/que0que.cc:1117(que_run_threads_low(que_thr_t*))[0x55a6a0758c35]

que/que0que.cc:1159(que_run_threads(que_thr_t*))[0x55a6a0758fde]

srv/srv0srv.cc:2561(srv_task_execute())[0x55a6a094083e]

srv/srv0srv.cc:2606(srv_worker_thread)[0x55a6a09409c4]