Method joinReference

packages/sql/src/query/QueryBuilder.ts:3009–3141

(
    field: string | RawQueryFragment | NativeQueryBuilder | QueryBuilder,
    alias: string,
    cond: Dictionary,
    type: JoinType,
    path?: string,
    schema?: string,
    subquery?: string,
  )

  }

  private joinReference(
    field: string | RawQueryFragment | NativeQueryBuilder | QueryBuilder,
    alias: string,
    cond: Dictionary,
    type: JoinType,
    path?: string,
    schema?: string,
    subquery?: string,
  ): { prop: EntityProperty<Entity>; key: string } {
    this.ensureNotFinalized();

    if (typeof field === 'object') {
      const prop = {
        name: '__subquery__',
        kind: ReferenceKind.MANY_TO_ONE,
      } as EntityProperty;

      if (field instanceof QueryBuilder) {
        prop.type = Utils.className(field.mainAlias.entityName);
        prop.targetMeta = field.mainAlias.meta!;
        field = field.getNativeQuery();
      }

      if (isRaw(field)) {
        field = this.platform.formatQuery(field.sql, field.params);
      }

      const key = `${this.alias}.${prop.name}#${alias}`;
      this.#state.joins[key] = {
        prop,
        alias,
        type,
        cond,
        schema,
        subquery: field.toString(),
        ownerAlias: this.alias,
      } as any;

      return { prop, key };
    }

    if (!subquery && type.includes('lateral')) {
      throw new Error(`Lateral join can be used only with a sub-query.`);
    }

    const [fromAlias, fromField] = this.helper.splitField(field as EntityKey<Entity>);
    const q = (str: string) => `'${str}'`;

    if (!this.#state.aliases[fromAlias]) {
      throw new Error(
        `Trying to join ${q(fromField)} with alias ${q(fromAlias)}, but ${q(fromAlias)} is not a known alias. Available aliases are: ${Object.keys(this.#state.aliases).map(q).join(', ')}.`,
      );
    }

    const entityName = this.#state.aliases[fromAlias].entityName;
    const meta = this.metadata.get(entityName);
    const prop = meta.properties[fromField];