Associative-array record member assignment is lost after assigning the record NULL

MariaDB 12.3.3 on Linux x86_64 loses a successful member assignment when an associative-array record element was first assigned NULL. Reading the element returns every member as NULL. The same member assignment works for a plain record and for an array element initialized with a record constructor.

This occurs when an Oracle-mode associative-array element containing a record is assigned NULL and then one of its members is assigned directly or through SELECT INTO.

Reproducer

Save the following as case.sql, then run mariadb --batch --raw < case.sql.

CREATE DATABASE record_test;

USE record_test;

SET sql_mode=ORACLE;

DELIMITER $$

DECLARE

  TYPE rec_t IS RECORD (x INT, y INT);

  TYPE arr_t IS TABLE OF rec_t INDEX BY INT;

  a arr_t;

  r rec_t;

BEGIN

  r := NULL;

  r.x := 7;

  SELECT 'plain_record' AS label, r.x AS x, r.y AS y;

  a(1) := NULL;

  a(1).x := 7;

  SELECT 'array_member' AS label, a(1).x AS x, a(1).y AS y;

  a(2) := rec_t(NULL,NULL);

  a(2).x := 7;

  SELECT 'constructor' AS label, a(2).x AS x, a(2).y AS y;

  a(3) := NULL;

  SELECT 9 INTO a(3).x;

  SELECT 'select_into' AS label, a(3).x AS x, a(3).y AS y;

END;

$$

DELIMITER ;

DROP DATABASE record_test;

Actual result

The direct assignment and SELECT INTO values disappear only for elements previously assigned NULL:

label           x     y

plain_record    7     NULL

array_member    NULL  NULL

constructor     7     NULL

select_into     NULL  NULL

The SQL completes without an error or server interruption.

Expected result

Assigning a(1).x := 7 successfully should make that record non-NULL and return (7,NULL), as demonstrated by the plain-record and constructor cases. Likewise, SELECT 9 INTO a(3).x should return (9,NULL). A successful child-member mutation must update the enclosing record's validity before it is serialized.

Analysis

Source inspection indicates that unpacking a NULL associative-array record marks both the enclosing record and its members NULL. The subsequent member mutation updates the child field without clearing the enclosing record's NULL state. Packing then observes the parent as NULL and omits member serialization, which explains why both direct assignment and SELECT INTO lose their values.