Aside from the SERVER-6310 mentioned by Matt Johnson, one other workaround is to use the $project operator to add or subtract from the UTC time zone to “shift the time” into the correct local zone. Turns out you can add or subtract time in milliseconds. For example, assuming I have a Date field called orderTime. … Read more
[*] It is not possible to do the type of computation you are describing with the aggregation framework – and it’s not because there is no $unwind method for non-arrays. Even if the person:value objects were documents in an array, $unwind would not help. The “group by” functionality (whether in MongoDB or in any relational … Read more
The main purpose of the aggregation framework is to ease the query of a big number of entries and generate a low number of results that hold value to you. As you have said, you can also use multiple find queries, but remember that you can not create new fields with find queries. On the … Read more
Yes it’s possible. You just use $geoNear instead. Beware the catches and read carefully. Presuming that your intent to is to store a field such as “travelDistance” to indicate on the document that any such searches must be “within” that supplied distance from the queried point to be valid. Then we simply query and evaluate … Read more
One way to do it is use $setWindowFields: db.collection.aggregate([ { $setWindowFields: { output: { totalCount: {$count: {}} } } }, { $unwind: “$items” }, { $group: { _id: “$items.defindex”, count: {$sum: 1}, totalCount: {$first: “$totalCount”} } }, { $project: { count: 1, usage: {$divide: [“$count”, “$totalCount”] } } }, {$sort: {count: -1}} ]) As you … Read more
what corresponds to the “case” SQL statement in the aggregation framework, is the $cond operator (see manual). $cond statements can be nested to simulate “when-then” and “else”, but I have chosen another approach, because it is easier to read (and to generate, see below): I’ll use the $concat operator to write the range string, which … Read more
This answer is outdated. Since version 3.2, MongoDB has limited support for left outer joins with the $lookup aggregation operator MongoDB does not do queries which span multiple collections – period. When you need to join data from multiple collections, you have to do it on the application level by doing multiple queries. Query collection … Read more
Since this is a text search query we are talking about then the most optimal form is this: db.collection.aggregate([ { “$match”: { “$text”: { “$search”: “cake tea” } } }, { “$sort”: { “score”: { “$meta”: “textScore” } } }, { “$limit”: skip + limit }, { “$skip”: skip } ]) The rationale on the … Read more
Check if this solution meets your requirements. Explanation We join over the same collection. So for each item i we take item i+1. This method gives us where presenceStatus has been changed. We filter documenti i+1 pairs where presenceStatus is 0 – 1 or 1 – 0. We group them into single data array. Now … Read more
Use $dateToParts and its counterpart $dateFromParts Here is an updated Playground What it does is basically break the date into its parts: { $project: { dateHour: { $dateToParts: { date: “$updatedAt” } } } } would produce: { “dateHour”: { “day”: 19, “hour”: 18, “millisecond”: 0, “minute”: 21, “month”: 3, “second”: 5, “year”: 2020 } … Read more