Implement Transactions to Support Begin / Commit / Rollback

[rognoni]

I created the nextval function that the first time creates a sequence collection and after increments its value:

nextval: 1
nextval: 2

========== sequence
{"schema":"info","entity":"history","property":"id","val":2,"_id":"3fd5cd0d081b280"}

but this function is not secure without the database transaction:

  nextval: function(schema, entity, property) {
    var sequenceCollection = this.fdb.db(schema).collection("sequence");
    var sequenceResult = sequenceCollection.find({
      schema: {
        "$eq": schema
      },
      entity: {
        "$eq": entity
      },
      property: {
        "$eq": property
      }
    });

    if (sequenceResult.length == 0) {
      sequenceCollection.insert({schema: schema, entity: entity, property: property, val: 1});
      return 1;
    } else {
      var val = sequenceResult[0].val + 1;
      sequenceCollection.updateById(sequenceResult[0]._id, {val: val});
      return val;
    }
  }

https://github.com/rognoni/adaptable/blob/master/Front-end/HTML5-Bootstrap4/database.js

[Irrelon]

Hey ya,

Could you clarify what you are asking? I don't know how to answer you at the moment.

Thanks!

Rob

[rognoni]

Yes, probably is not simple to implement this feature into ForerunnerDB (using pure JavaScript)

https://en.wikipedia.org/wiki/Database_transaction

but for example IndexedDB uses the transaction concepts:

var objectStore = db.transaction(["customers"], "readwrite").objectStore("customers");
var request = objectStore.get("444-44-4444");
request.onerror = function(event) {
  // Handle errors!
};
request.onsuccess = function(event) {
  // Get the old value that we want to update
  var data = request.result;

  // update the value(s) in the object that you want to change
  data.age = 42;

  // Put this updated object back into the database.
  var requestUpdate = objectStore.put(data);
   requestUpdate.onerror = function(event) {
     // Do something with the error
   };
   requestUpdate.onsuccess = function(event) {
     // Success - the data is updated!
   };
};

https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API/Using_IndexedDB#Updating_an_entry_in_the_database

[Irrelon]

Ahh I SEE... you are asking if we can implement transactions... sorry that was definitely not clear from your first post!

It is possible. It is on the roadmap (I think). You are correct that it could be quite complex though :)

[rognoni]

I found now this project if can help:

https://github.com/yathit/ydn-db#transaction