fix: atomic updates should always do a select with nested operations

[Weakky]

Overview

fixes prisma/prisma#20491

Before this PR, the following query:

mutation {
  updateOnePost(
    where: { id: 1 },
    data: {
      author: { update: { id: 42 } }
    }) {
    id
    authorId
  }
}

Would result in the following SQL queries:

BEGIN
SELECT id, authorId FROM "Post" WHERE id = 1;
UPDATE "User" SET id = 42 WHERE id = 1;
COMMIT

Where the first SELECT would be used as the result. Unfortunately in this case (and other cases such as with a disconnect or delete), the nested update alters the foreign key and so the returned authorId would not reflect the actual update.

For this reason (and for simplicity atm), we've decided to bring back the post SELECT as soon as there are any nested mutations in an update. Therefore, the client query above will now result in the following SQL queries:

BEGIN
SELECT id, authorId FROM "Post" WHERE id = 1;
UPDATE "User" SET id = 42 WHERE id = 1;
SELECT id, authorId FROM "Post" WHERE id = 1;
COMMIT

[codspeed-hq]

CodSpeed Performance Report

Merging #4100 will not alter performance

_{Comparing fix/to-one-fks-update (797b093) with main (a9b7003)}

Summary

✅ 11 untouched benchmarks