Loading grandchild relations

JavaScript
1

I need to coalesce data from three tables into one data structure. One record in the first table has a relation to 103 records in the second table. Each of the 103 records have relations to 0-to-N records in the third table. How can I get all three related tables in fewer than 104 calls, preferably 1 or 2?

Thank you,
Kelly

2

Hello @Kelly_Oglesby ,

Assuming you have 3 tables: Parent - 1:N (children) → Child - 1:N (grandchilds) → Grandchild,
I can suggest you following solution:

  const MAX_PAGE_SIZE = 100

  async function findAllRecords(tableName, query) {
    const total = await Backendless.Data.of(tableName).getObjectCount(query && query.where)

    const itemsList = []

    const requests = []

    let currentQuery = {
      ...query,
      pageSize: MAX_PAGE_SIZE,
      offset  : 0
    }

    while (currentQuery.offset < total) {
      requests.push(Backendless.Data.of(tableName).find(currentQuery))

      currentQuery = {
        ...currentQuery,
        offset: currentQuery.offset + MAX_PAGE_SIZE
      }
    }

    const results = await Promise.all(requests)

    results.forEach(items => {
      items.forEach(item => {
        itemsList.push(item)
      })
    })

    return itemsList
  }

  const parent = await Backendless.Data.of('Parent').findFirst() // assume you already have some parent records

  const children = await findAllRecords('Child', {
    where            : `Parent[children].objectId = '${ parent.objectId }'`,
    relations        : ['grandchilds'],
    relationsPageSize: 100
  })
  
  // each child will have grandchilds array

Regards,
Stanislaw