I was tasked with migrating data found in an array containing a series of arrays of objects within the documents of our Firestore database to a subcollection. The purpose of this migration was to improve the management of this information, making it easier to filter, edit, and delete this data. I developed a function to filter the documents that had some data within these arrays and soon found over 500 documents to migrate. To solve this problem, I developed a JavaScript logic that involved separating this data into an object called "data" and also obtaining the document's ID to which this data belonged. Then, I saved this data in the subcollection of the document with that ID.

Snippet of code to retrieve documents in the collection:

const q = query(
  collection(db, "clientes"),
  where("empresa", "!=", "teste")
);
const querySnapshot = await getDocs(q);

Snippet of code where i filter the necessary data from each document:

let clientes = [];
querySnapshot.forEach((doc) => {
  const acessos = doc.data().acessos;

  if (acessos && typeof acessos === "object") {
    Object.entries(acessos).forEach(([categoria, objetos]) => {
      if (Array.isArray(objetos)) {
        objetos.forEach((objeto) => {
          const {
            email = "",
            nome = "",
            observacao = "",
            senha = "",
          } = objeto || {};

          let cliente = {
            id: doc.id,
            razaoSocial: doc.data().razaoSocial,
            categoria,
            email,
            nome,
            observacao,
            senha,
          };
          clientes.push(cliente);
        });
      } else {
        const {
          email = "",
          nome = "",
          observacao = "",
          senha = "",
        } = objetos || {};

        let cliente = {
          id: doc.id,
          razaoSocial: doc.data().razaoSocial,
          categoria,
          email,
          nome,
          observacao,
          senha,
        };
        clientes.push(cliente);
      }
    });
  }
});

return clientes;

Function I used to retrieve and separate the data, and then register it in the subcollection with the registerAccess() function:

async function fetchCustomersWithAccess() {
  const result = await listCustomersWithAccess();
  result.forEach((doc) => {
    const data = {
      categoria: doc.categoria,
      email: doc.email,
      nome: doc.nome,
      observacao: doc.observacao,
      senha: doc.senha,
    };

    const docId = doc.id;

    registerAccess(docId, data);
  });
}