Convert MySQL JSON array with unpredictable keys to a table, and join - json

Question

Given the following MySQL 8 table structures...
CREATE TABLE `products` (
`id` bigint unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(1000) NOT NULL,
PRIMARY KEY (`id`)
);
/* the "names" of the custom attributes that could exist for any given product */
CREATE TABLE `custom_attributes` (
`id` bigint unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
);
/* the custom attributes of products stored as json array, when "key" is FK to custom_attributes table, and "value" is the attribute value for the given product */
/* in an ideal design, this table would not exist as there is a one-to-one relationship with `product`, and so could have simply been an `attributes` column in the product table, but we are where we are... */
CREATE TABLE `product_custom_attributes` (
`id` bigint unsigned NOT NULL AUTO_INCREMENT,
`product_id` bigint unsigned NOT NULL,
`attribute_value` json DEFAULT NULL,
PRIMARY KEY (`id`),
CONSTRAINT `product_custom_attributes_product_id_foreign` FOREIGN KEY (`product_id`) REFERENCES `products` (`id`)
);
...and the following data...
INSERT INTO products (`id`, `name`) VALUES (1, 'Big Blue Ball');
INSERT INTO products (`id`, `name`) VALUES (2, 'Small Wooden Bat');
INSERT INTO custom_attributes (`id`, `title`) VALUES (1, 'Size');
INSERT INTO custom_attributes (`id`, `title`) VALUES (2, 'Color');
INSERT INTO custom_attributes (`id`, `title`) VALUES (3, 'Material');
INSERT INTO custom_attributes (`id`, `title`) VALUES (4, 'Height');
INSERT INTO product_custom_attributes (`id`, `product_id`, `attribute_value`) VALUES (1, 1, '{"1": "Big", "2": "Blue"}');
INSERT INTO product_custom_attributes (`id`, `product_id`, `attribute_value`) VALUES (2, 2, '{"1": "Small", "3": "Wood"}');
...how can I write a query to return the following results...?
product_id
name
Size
Color
Material
Height
1
Big Blue Ball
Big
Blue
2
Small Wooden Bat
Small
Wood
I cannot predict, at runtime, what custom_attributes might exist for products because it's likely this list will change over time, e.g. new attributes added.
I'm pretty sure I'll need to use the JSON_TABLE() function, but I've struggled to get result with the unpredicatable attributes (and therefore unpredictable JSON "columns") in play.
Edit - Solution
SET SESSION group_concat_max_len=4294967295;
SET #sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'MAX(IF(ca.title = ''',
ca.title,
''', attribute_values.attribute_value, NULL)) AS `',
ca.title, '`'
)
) INTO #sql
FROM
products p
LEFT OUTER JOIN custom_attributes ca ON p.project_id = ca.project_id
LEFT OUTER JOIN product_custom_attributes pca ON p.id = pca.product_id
LEFT OUTER JOIN JSON_TABLE(
JSON_KEYS(pca.attribute_value),
'$[*]' COLUMNS (
rn FOR ORDINALITY,
attribute_key VARCHAR(255) PATH '$'
)
) attribute_keys ON ca.id = attribute_keys.attribute_key
LEFT OUTER JOIN JSON_TABLE(
JSON_EXTRACT(pca.attribute_value, '$.*'),
'$[*]' COLUMNS (
rn FOR ORDINALITY,
attribute_value VARCHAR(255) PATH '$'
)
) attribute_values ON attribute_values.rn = attribute_keys.rn;
-- if there are no custom attributes #sql will be NULL and when appended to the following query will make the whole thing NULL, so deal with this...
SET #sql = CASE WHEN ISNULL(#sql) THEN '' ELSE CONCAT(', ', #sql) END;
SET #sql = CONCAT('
SELECT
p.id
, p.name
', #sql, '
FROM
products p
LEFT OUTER JOIN custom_attributes ca ON p.project_id = ca.project_id
LEFT OUTER JOIN product_custom_attributes pca ON p.id = pca.product_id
LEFT OUTER JOIN JSON_TABLE(
JSON_KEYS(pca.attribute_value),
''$[*]'' COLUMNS (
rn FOR ORDINALITY,
attribute_key VARCHAR(255) PATH ''$''
)
) attribute_keys ON ca.id = attribute_keys.attribute_key
LEFT OUTER JOIN JSON_TABLE(
JSON_EXTRACT(pca.attribute_value, ''$.*''),
''$[*]'' COLUMNS (
rn FOR ORDINALITY,
attribute_value VARCHAR(255) PATH ''$''
)
) attribute_values ON attribute_values.rn = attribute_keys.rn
GROUP BY p.id, p.name');
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;