MongoDB:仅当集合自时间点以来没有更新的文档时,才在集合中插入文档

findAndModify

oldTimestamp

db.collection.findAndModify({
    query: {timestamp: {$gt: oldTimestamp}},
    new: true, // Return modified / inserted document
    upsert: true, // Update if match found, insert otherwise
    update: {
         $setOnInsert: {..your document...}
    }
})

collection.findAndModify(criteria[, sort[, update[, options]]], callback)

example

db.collection('test').findAndModify(
  {timestamp: {$gt: oldTimestamp}}, // query, timestamp is a property of your document, often set as the created time
  [['timestamp','desc']],  // sort order
  {$setOnInsert: {..your document..}}, // replacement, replaces only the field "hi"
  {
      new: true,
      upsert: true
  }, // options
  function(err, object) {
      if (err){
          console.warn(err.message);  // returns error if no matching object found
      }else{
          console.dir(object);
      }
  });
});

timestamp Mongoose Pre Save path validation hook

YourSchema.path('timestamp').validate(function(value, done) {
  this.model(YourSchemaModelName).count({ timestamp: {$gt : value} }, function(err, count) {
    if (err) {
        return done(err);
    }
    // if count exists and not zero hence document is found with greater timestamp value
    done(!count);
});
}, 'Greater timestamp already exists');

timestamp

db.collection.find({}, {timestamp: 1, _id:0}).sort({timestamp:-1}).limit(1)

covered query