InsertMany then Find will raise duplicate key value violates unique constraint

[dungkaka]

Describe the bug
I use insertMany to insert multiple record, but if I find right after insertMany, it cause duplicate key value violates unique constraint.

Code describe

await this.em.insertMany(
    City,
    mongoCities.map((city) => this.em.create(City, city as any))
);

// Stop here will not raise error
// But if continute run below find code, it will raise duplicate key value violates unique constraint

const cities = await this.em.find(City, {});

Expected behavior
After insertMany, I can find without cause error !

Versions

Dependency	Version
node	16
mikro-orm	5.8

[dungkaka]

Give many thanks to this author of awesome lib.
Btw, I also want to know the difference between these two ways to insertMany, about what happens inside, performance? :

1. Insert many created entity.

await this.em.insertMany(
          City,
          mongoCities.map((city) => this.em.create(City, city as any))
      );

2. Persist multiple created entity then flush

mongoCities.forEach((city) => {
    const _city = this.em.create(City, city as any);
    this.em.persist(_city);
});
await this.em.flush();

[B4nan]

This is not reproducible, sounds like you are using different EM forks (= different contexts), and auto-flush gets triggered by the em.find(). WIll be happy to help if you provide complete repro, but this is a misusage most probably.

Note that you are not using the method correctly, this is how it's supposed to be used:

// no need to create entity instances yourseft
await this.em.insertMany(City, mongoCities);

// or create the instances and provide them in the first parameter
const entities = mongoCities.map((city) => this.em.create(City, city as any));
await this.em.insertMany(entities);

Btw, you shouldn't need the as any cast, sounds like either wrong input type or wrong entity definition.

The difference between insertMany and flushing is that insertMany won't affect the context anyhow, it's a different approach. On the other hand, using em.create() will automatically call persist on the just created entity, and as such, flushing will insert that too - that is probably what is happening to you, as you use em.create(), leave the entity in the context, and instead of flushing, you use insertMany - that just issues the insert query, but keeps the context populated, and the following find call triggers a flush for those. I guess we could ensure the right state on the entity instances after you do the insertMany, but it is still a misusage imo.

---

Actually, yes, this is exactly what is happening to you, you are just mixing two approaches. This should help: 94eed5e?w=1