Indexes in sub-document for mongodb

[anlauren]

Describe the bug
It seems that mikro-orm mondodb driver doesn't support sub-document indexing. That makes sense for SQL but it's common practice in mongodb. It looks like it's not possible to create an index like myField.mySubField.
Now it could be because of how i've written the embedding that's it's not working.
Stack trace

[Nest] 79737   - 08/16/2021, 11:19:23 AM   [ExceptionHandler] Entity Test has wrong index definition: 'testEmbedded.a' does not exist. You need to use property name, not column name. +47ms
MetadataError: Entity Test has wrong index definition: 'testEmbedded.a' does not exist. You need to use property name, not column name.
    at Function.unknownIndexProperty (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/errors.js:126:16)
    at MetadataValidator.validateIndexes (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/metadata/MetadataValidator.js:109:50)
    at MetadataValidator.validateEntityDefinition (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/metadata/MetadataValidator.js:26:14)
    at MetadataDiscovery.processEntity (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:297:24)
    at filtered.forEach.meta (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:52:63)
    at Array.forEach (<anonymous>)
    at MetadataDiscovery.discover (/Users/antoinelaurent/virtual-event-service/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:52:18)
    at process._tickCallback (internal/process/next_tick.js:68:7)

To Reproduce
Steps to reproduce the behavior:

@Embeddable()
export class TestEmbedded {
  @Property()
  a: number;
}

@Entity({ tableName: 'test' })
@Index({ properties: ['testEmbedded.a'] })
export class Test extends BaseEntity {
  @Embedded({
    entity: () => TestEmbedded,
    object: true,
  })
  testEmbedded: TestEmbedded;
}

Expected behavior
Should be able to use a . notation in mongodb indexes

Additional context
My original problem arises when i tried to create a compound index with a sub-field and a field of a document.

Versions

Dependency	Version
node	v10.22.0
typescript	v4.0.5
mikro-orm	v4.3.4
@mikro-orm/mongodb	v4.3.4

[B4nan]

Indeed, this is not supported -> this is a feature request, not a bug report.

[andrey-hohlov]

Hi, @B4nan
Any plans on it?

It works for @Index decorator :

@Index({ options: { 'embedded.property': 1 } })

But nothing works for @Unique.

[B4nan]

Fastest way to see this happen is sending a PR 🤷

[bebjakub]

@andrey-hohlov This works for a unique index, also with a sparse index if needed...

@Property({ nullable: true, unique: true })

more #4495

[B4nan]

Interesting, maybe this got fixed by some unrelated change over time. Will keep this open till we have some explicit tests for it so we can be sure it actually works (and it will remain working over time as well)

[B4nan]

Okay, this apparently works as expected, not sure what fixed it. Added tests to ensure it really works, will mark it as a feature commit so it gets into the changelog, although it will just add the test.