Simple Chat Room in NodeJS, expressJS and mongoDB in Docker Swarm
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4 years ago
'use strict';
const AggregateOperation = require('./aggregate');
class CountDocumentsOperation extends AggregateOperation {
constructor(collection, query, options) {
const pipeline = [{ $match: query }];
if (typeof options.skip === 'number') {
pipeline.push({ $skip: options.skip });
}
if (typeof options.limit === 'number') {
pipeline.push({ $limit: options.limit });
}
pipeline.push({ $group: { _id: 1, n: { $sum: 1 } } });
super(collection, pipeline, options);
}
execute(server, callback) {
super.execute(server, (err, result) => {
if (err) {
callback(err, null);
return;
}
// NOTE: We're avoiding creating a cursor here to reduce the callstack.
const response = result.result;
if (response.cursor == null || response.cursor.firstBatch == null) {
callback(null, 0);
return;
}
const docs = response.cursor.firstBatch;
callback(null, docs.length ? docs[0].n : 0);
});
}
}
module.exports = CountDocumentsOperation;