Initially brought up here: #4998 (comment)

Problem

The fact that the createMany API does not return the created records (which should be possible for Postgres) makes it difficult/impossible to use in some circumstances, meaning we must fall back to raw SQL. Here's an example.

Let's say I have these two tables

CREATE TABLE IF NOT EXISTS post (
  "id" SERIAL PRIMARY KEY,
  ...
);

CREATE TABLE IF NOT EXISTS comment (
  "id" SERIAL PRIMARY KEY,
  "postId" INTEGER NOT NULL REFERENCES post ("id") ON DELETE CASCADE,
  ...
);

Let's say I want to create many posts and many comments. The data to be created could be represented like so: Array<{post: PostData, comments: Array<CommentData>}>. If createMany returned the created data, I could do something like this:

const inputs: Array<{post: PostData, comments: Array<CommentData>}> = [...];
const posts = prisma.post.createMany({data: [...]});
const commentCreateData = inputs.map((input, index) => input.comments.map((commentData) => ...))).flat();
prisma.comment.createMany({data: commentCreateData});

However, since createMany does not return the created data, it is difficult to create many posts and then create many comments linked to those posts in an efficient manner. The remaining options are to create records one-by-one or use raw SQL. Using a combination of createMany and findMany is possible if you manually specify IDs, but does not work if you rely on Postgres (or some other DB) to generate IDs by default.

Suggested solution

createMany should return an array of created records (like how create returns the single created record).

Alternatives

• Use create (inefficient if creating many records)
• Use raw SQL (efficient but inconvenient)
• Use createMany + findMany (only works if you manually specify IDs, and also less efficient than if createMany returned created records)

Additional context

Personally, I've used raw SQL as a workaround since it's the most efficient alternative.