Getting metadata for operations

[kbadk]

I recently requested metadata to be included in sharedb-mongo and it was made possible shortly after by adding an options parameter.

However, I'm not quite sure how to actually get the metadata out. The options parameter was added to ShareDbMongo.prototype.getOps:

ShareDbMongo.prototype.getOps = function(collectionName, id, from, to, options, callback) {
  var self = this;
  this._getSnapshotOpLink(collectionName, id, function(err, doc) {
    if (err) return callback(err);
    if (doc) {
      if (isCurrentVersion(doc, from)) {
        return callback(null, []);
      }
      var err = doc && checkDocHasOp(collectionName, id, doc);
      if (err) return callback(err);
    }
    self._getOps(collectionName, id, from, options, function(err, ops) {
      if (err) return callback(err);
      var filtered = filterOps(ops, doc, to);
      var err = checkOpsFrom(collectionName, id, filtered, from);
      if (err) return callback(err);
      callback(null, filtered);
    });
  });
};

But unfortuntaely, the options don't seem to be passed over from ShareDB itself. Backend.prototype.getOps does not take any options parameter and just passes through null as options to sharedb-mongo (through backend.db.getOps):

Backend.prototype.getOps = function(agent, index, id, from, to, callback) {
  var start = Date.now();
  var projection = this.projections[index];
  var collection = (projection) ? projection.target : index;
  var backend = this;
  var request = {
    agent: agent,
    index: index,
    collection: collection,
    id: id,
    from: from,
    to: to
  };
  backend.db.getOps(collection, id, from, to, null, function(err, ops) {
    if (err) return callback(err);
    backend._sanitizeOps(agent, projection, collection, id, ops, function(err) {
      if (err) return callback(err);
      backend.emit('timing', 'getOps', Date.now() - start, request);
      callback(err, ops);
    });
  });
};

How am I supposed to pass options (to get metadata) to sharedb-mongo without modifying the ShareDB source code?

[kbadk]

Is this being addressed?

[curran]

Can you get them out via a straight up Mongo query?

[kbadk]

@curran It's in the database, so sure, I suppose you could. However, when I've needed it, I've just changed L239 in ./lib/backend.js:

backend.db.getOps(collection, id, from, to, null, function(err, ops) {

to

backend.db.getOps(collection, id, from, to, { metadata: 1 }, function(err, ops) {

It gets the job done, but it's quite nasty to modify the library, and something you have to remember to do every time you update sharedb, but since the project is dead now, well...

[curran]

@kbadk Oh nice! Thanks for sharing that snippet.

It would be great to add a way of passing the options in through ShareDB. Maybe one more argument can be added to Backend.prototype? So the signature could be:

• Backend.prototype.getOps = function(agent, index, id, from, to, callback)
• or Backend.prototype.getOps = function(agent, index, id, from, to, options, callback)

Would you be willing to put together a PR that does something like this?

@nateps Any thoughts on an enhancement like this? Would a PR be welcome? Introducing a change like this would help improve the perception that ShareDB is a dead project, which seems to be quite widespread.

[alecgibson]

This would be solved by: #215