[SamJUK]

Description (*)

Saving a product deletes all of its product links (related, up-sell, cross-sell, grouped) and inserts them again, even when none of them changed. Product::afterSave() always calls Link\SaveHandler::execute(), which deleted every existing link before saving the product's link set. When no links are passed, that set is lazy-loaded from the database, so it is the same links.

Each save therefore uses new catalog_product_link ids and fires the mview triggers on that table. On a 2.4.7 store receiving frequent product updates over REST, catalog_product_link.link_id had reached about 2.02 billion for 140k rows, and the changelogs fed by those triggers held billions of rows.

• SaveHandler deletes only the links that are no longer in the product's link set. Kept links go through ProductLinkRepository::save(), which already updates an existing link in place.
• Link::saveProductLinks() skips attribute values that are already stored. INSERT ... ON DUPLICATE KEY UPDATE uses an auto increment id even when it only updates, so unchanged saves still used up catalog_product_link_attribute_* ids. An omitted attribute is only deleted when a value is stored.

Measured over REST (PUT /V1/products/:sku, indexers on Update by Schedule, a product with 6 links):

Save	Before: link ids / attribute ids / changelog rows	After
No product_links in the payload	6 / 6 / 71	0 / 0 / 11
The same product_links sent again	6 / 6 / 67	0 / 0 / 7
One link removed, one added	6 / 6 / 67	1 / 1 / 17

The changelog rows left after the change come from the product's own attributes.

link_id is now stable across saves, so code that relied on links being re-created on every save will see fewer deletes and inserts.

Related Pull Requests

#41202 takes the same approach for custom options (#39652).

Fixed Issues (if relevant)

1. Fixes Saving a product deletes and re-inserts all of its product links #41703

Manual testing scenarios (*)

1. Set the indexers to Update by Schedule: bin/magento indexer:set-mode schedule.
2. Create simple products A, B, C and D, and give A the related products B (position 1) and C (position 2).
3. Note A's links with SELECT link_id, linked_product_id FROM catalog_product_link WHERE product_id = <A's id>, and the row count of catalogsearch_fulltext_cl.
4. PUT /V1/products/A with {"product": {"sku": "A", "price": 12}}.
5. Expected: the same link_id values, and no changelog rows from catalog_product_link. Before this change, every link gets a new link_id.
6. PUT /V1/products/A with product_links for B (position 2) and D. Expected: C's link is removed, D's is added, and B keeps its link_id with position 2.
7. For a grouped product, change one associated product's qty through product_links. Expected: the new qty is saved and both links keep their link_id.

Questions or comments

Tested on MariaDB 10.6. Not tested on Adobe Commerce (row_id and staging).

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[SamJUK]

@magento run all tests