Method applyTPTJoins

packages/sql/src/query/QueryBuilder.ts:3579–3615

* For TPT (Table-Per-Type) inheritance: INNER JOINs parent tables. * When querying a child entity, we need to join all parent tables. * Field selection is handled separately in addTPTParentFields().

()

   * Field selection is handled separately in addTPTParentFields().
   */
  private applyTPTJoins(): void {
    const meta = this.mainAlias.meta;

    if (
      meta?.inheritanceType !== 'tpt' ||
      !meta.tptParent ||
      ![QueryType.SELECT, QueryType.COUNT].includes(this.type)
    ) {
      return;
    }

    if (this.#state.tptJoinsApplied) {
      return;
    }
    this.#state.tptJoinsApplied = true;

    let childMeta: EntityMetadata = meta;
    let childAlias = this.mainAlias.aliasName;

    while (childMeta.tptParent) {
      const parentMeta = childMeta.tptParent;
      const parentAlias = this.getNextAlias(parentMeta.className);
      this.createAlias(parentMeta.class, parentAlias);
      this.#state.tptAlias[parentMeta.className] = parentAlias;

      this.addPropertyJoin(
        childMeta.tptParentProp!,
        childAlias,
        parentAlias,
        JoinType.innerJoin,
        `[tpt]${childMeta.className}`,
      );

      childMeta = parentMeta;
      childAlias = parentAlias;
    }
  }

  /**
   * For TPT inheritance: adds field selections from parent tables.