Issue description

Fetching relations on TreeRepository's method findDescendants() uses JOIN strategy instead of QUERY strategy to load relations, even if DataSource's relationLoadStrategy is set to 'query'

Expected Behavior

This is a custom implementation where fetching a TreeRepository with nested relations is required. The expected query built from this method should be a series of different queries to gather all the required rows

Actual Behavior

The raw query results in a complex query with multiple LEFT JOINS to fetch all the corresponding relations. This is causing a memory heap allocation error on my application.

This is the resulting query:

web: query: SELECTtreeEntity.idAStreeEntity_id, treeEntity.deletedAtAStreeEntity_deletedAt, treeEntity.nameAStreeEntity_name, treeEntity.valueAStreeEntity_value, treeEntity.value_typeAStreeEntity_value_type, treeEntity.typeAStreeEntity_type, treeEntity.parentIdAStreeEntity_parentId, treeEntity.priorityAStreeEntity_priority, treeEntity.mpathAStreeEntity_mpath, treeEntity__rules.idAStreeEntity__rules_id, treeEntity__rules.deletedAtAStreeEntity__rules_deletedAt, treeEntity__rules.factIdAStreeEntity__rules_factId, treeEntity__rules.actionAStreeEntity__rules_action, treeEntity__rules.valueAStreeEntity__rules_value, treeEntity__rules.nodeIdAStreeEntity__rules_nodeId, treeEntity__rules__fact.idAStreeEntity__rules__fact_id, treeEntity__rules__fact.deletedAtAStreeEntity__rules__fact_deletedAt, treeEntity__rules__fact.nameAStreeEntity__rules__fact_name, treeEntity__rules__fact.keyAStreeEntity__rules__fact_key, treeEntity__rules__fact.hintAStreeEntity__rules__fact_hint, treeEntity__rules__fact.isActiveAStreeEntity__rules__fact_isActive, treeEntity__rules__fact.typeAStreeEntity__rules__fact_type, treeEntity__rules__fact.treeIdAStreeEntity__rules__fact_treeId, treeEntity__rules_fact.idAStreeEntity__rules_fact_id, treeEntity__rules_fact.deletedAtAStreeEntity__rules_fact_deletedAt, treeEntity__rules_fact.nameAStreeEntity__rules_fact_name, treeEntity__rules_fact.keyAStreeEntity__rules_fact_key, treeEntity__rules_fact.hintAStreeEntity__rules_fact_hint, treeEntity__rules_fact.isActiveAStreeEntity__rules_fact_isActive, treeEntity__rules_fact.typeAStreeEntity__rules_fact_type, treeEntity__rules_fact.treeIdAStreeEntity__rules_fact_treeId, treeEntity__evaluationNodes.idAStreeEntity__evaluationNodes_id, treeEntity__evaluationNodes.deletedAtAStreeEntity__evaluationNodes_deletedAt, treeEntity__evaluationNodes.processedAtAStreeEntity__evaluationNodes_processedAt, treeEntity__evaluationNodes.resultAStreeEntity__evaluationNodes_result, treeEntity__evaluationNodes.orderAStreeEntity__evaluationNodes_order, treeEntity__evaluationNodes.evaluationTypeAStreeEntity__evaluationNodes_evaluationType, treeEntity__evaluationNodes.nodeIdAStreeEntity__evaluationNodes_nodeId, treeEntity__evaluationNodes.evaluationIdAStreeEntity__evaluationNodes_evaluationId, treeEntity__evaluationNodes__evaluation.idAStreeEntity__evaluationNodes__evaluation_id, treeEntity__evaluationNodes__evaluation.deletedAtAStreeEntity__evaluationNodes__evaluation_deletedAt, treeEntity__evaluationNodes__evaluation.processedAtAStreeEntity__evaluationNodes__evaluation_processedAt, treeEntity__evaluationNodes__evaluation.simulatedAStreeEntity__evaluationNodes__evaluation_simulated, treeEntity__evaluationNodes__evaluation.payloadAStreeEntity__evaluationNodes__evaluation_payload, treeEntity__evaluationNodes__evaluation.resultAStreeEntity__evaluationNodes__evaluation_result, treeEntity__evaluationNodes__evaluation.referenceIdAStreeEntity__evaluationNodes__evaluation_referenceId, treeEntity__evaluationNodes__evaluation.referenceEntityAStreeEntity__evaluationNodes__evaluation_referenceEntity, treeEntity__evaluationNodes__evaluation.versionIdAStreeEntity__evaluationNodes__evaluation_versionIdFROMnode treeEntityLEFT JOINrule treeEntity__rulesONtreeEntity__rules.nodeId=treeEntity.id AND (treeEntity__rules.deletedAtIS NULL) LEFT JOINfact treeEntity__rules__factONtreeEntity__rules__fact.id=treeEntity__rules.factId AND (treeEntity__rules__fact.deletedAtIS NULL) LEFT JOINfact treeEntity__rules_factONtreeEntity__rules_fact.id=treeEntity__rules.factId AND (treeEntity__rules_fact.deletedAtIS NULL) LEFT JOINevaluationNode treeEntity__evaluationNodesONtreeEntity__evaluationNodes.nodeId=treeEntity.id AND (treeEntity__evaluationNodes.deletedAtIS NULL) LEFT JOINevaluation treeEntity__evaluationNodes__evaluationONtreeEntity__evaluationNodes__evaluation.id=treeEntity__evaluationNodes.evaluationId AND (treeEntity__evaluationNodes__evaluation.deletedAtIS NULL) WHERE (treeEntity.mpathLIKE CONCAT((SELECTNode.mpathASpathFROMnode NodeWHERE (Node.idIN (?) ) AND (Node.deletedAtIS NULL )), '%') ) AND (treeEntity.deletedAtIS NULL ) -- PARAMETERS: [19805]

Steps to reproduce

This is the implementation causing the problem.
let nodes = await this.dataSource.manager .getTreeRepository(Node) .findDescendants(node, { relations: [ 'rules', 'rules.fact', 'evaluationNodes', 'evaluationNodes.evaluation', ], });
Here are the entities involved (I'm just providing relevant cols)

`
@entity('rule')
export class Rule extends DefaultEntity {
@manytoone(() => Fact, (fact) => fact.rules, { eager: true })
fact?: Fact;

@Column()
factId?: number;

@ManyToOne(() => Node, (node) => node.rules)
node?: Node;

// Node.entity.ts
@entity('node')
@TreeDecorator('materialized-path')
export class Node extends DefaultEntity {
@TreeChildren({ cascade: true })
children?: Node[];

@Column()
parentId?: number;

@TreeParent()
parent?: Node;

@OneToMany(() => Rule, (rule) => rule.node, {
	cascade: true,
	onDelete: 'CASCADE',
})
rules?: Rule[];

@OneToMany(() => EvaluationNode, (evaluation) => evaluation.node)
evaluationNodes?: EvaluationNode[];

@OneToOne(() => Version, (version) => version.tree)
version?: Version;

}
`

`
@entity('evaluationNode')
export class EvaluationNode extends DefaultEntity {

@Column()
nodeId!: number;

@ManyToOne(() => Node, (node) => node.evaluationNodes)
node?: Node;

// PARENT
@ManyToOne(() => Evaluation, (evaluation) => evaluation.evaluationNodes)
evaluation?: Evaluation;

}
`

My Environment

Additional Context

I know that a similar situation was addressed and resolved regarding the relationLoadStrategy for regular repositories. Maybe this change needs to be replicated into the TreeRepository? I could help writting the PR, but I just need a little insight on where to start

Relevant Database Driver(s)

• aurora-mysql
• aurora-postgres
• better-sqlite3
• cockroachdb
• cordova
• expo
• mongodb
• mysql
• nativescript
• oracle
• postgres
• react-native
• sap
• spanner
• sqlite
• sqlite-abstract
• sqljs
• sqlserver

Are you willing to resolve this issue by submitting a Pull Request?

Yes, I have the time, but I don't know how to start. I would need guidance.