Bucket pattern for time-series data in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a bucket field that groups timestamps by hour.

MongoDB

db.sensorData.aggregate([{ $addFields: { bucket: { $dateTrunc: { date: "$timestamp", unit: [1] } } } }])

Drag options to blanks, or click blank then click option'

Ahour

Bminute

Cday

Dsecond

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'minute' or 'second' will create too many small buckets.

Using 'day' groups data by whole days, not hours.

The $dateTrunc operator truncates the timestamp to the specified unit. Using "hour" groups data into hourly buckets.

2fill in blank

medium

Complete the code to group documents by the bucket field and count entries per bucket.

MongoDB

db.sensorData.aggregate([{ $group: { _id: "$[1]", count: { $sum: 1 } } }])

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Atimestamp

BsensorId

Cbucket

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Grouping by 'timestamp' groups by exact time, not buckets.

Grouping by 'sensorId' groups by sensor, not time.

Grouping by the bucket field groups documents into time buckets, allowing counting entries per bucket.

3fill in blank

hard

Fix the error in the pipeline stage that filters documents within a specific bucket range.

MongoDB

db.sensorData.aggregate([{ $match: { bucket: { $gte: ISODate("2023-01-01T00:00:00Z"), [1]: ISODate("2023-01-01T23:59:59Z") } } }])

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A$lte

B$lt

C$eq

D$ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt excludes documents exactly at the upper bound.

Using $eq or $ne does not specify a range.

To filter documents between two dates inclusive, use $gte and $lte operators.

4fill in blank

hard

Fill both blanks to create a bucket pattern that groups data by day and calculates average value.

MongoDB

db.sensorData.aggregate([{ $addFields: { bucket: { $dateTrunc: { date: "$timestamp", unit: [1] } } } }, { $group: { _id: "$bucket", avgValue: { $[2]: "$value" } } }])

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Aday

Bhour

Cavg

Dsum

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hour' groups by hour, not day.

Using 'sum' adds values instead of averaging.

Grouping by day buckets groups data daily. Using avg calculates the average value per day.

5fill in blank

hard

Fill all three blanks to create a bucket pattern that groups data by month, counts entries, and filters buckets with more than 100 entries.

MongoDB

db.sensorData.aggregate([{ $addFields: { bucket: { $dateTrunc: { date: "$timestamp", unit: [1] } } } }, { $group: { _id: "$bucket", count: { $[2]: 1 } } }, { $match: { count: { $[3]: 100 } } }])

Drag options to blanks, or click blank then click option'

Amonth

Bsum

C$gt

Dday

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'day' instead of 'month' groups by day.

Using '$lt' instead of '$gt' filters wrong buckets.

Using 'avg' instead of 'sum' does not count entries.

Grouping by month buckets groups data monthly. Using sum counts entries. Filtering with $gt selects buckets with more than 100 entries.