Aggregation Pipeline

Aggregation Pipeline

Stages

The following 34 aggregation pipeline stages are supported:

Stage	Description
$match	Filter documents
$project	Reshape documents (include, exclude, compute fields)
$addFields / $set	Add or overwrite fields
$unset	Remove fields
$group	Group by key with accumulators
$sort	Sort documents
$limit	Limit number of documents
$skip	Skip documents
$unwind	Deconstruct array field
$lookup	Left outer join to another collection
$replaceRoot / $replaceWith	Replace document with a sub-document
$count	Count documents
$sortByCount	Group, count, and sort
$sample	Random sample
$facet	Multiple sub-pipelines in parallel
$bucket	Categorize into buckets
$bucketAuto	Auto-bucket by count
$unionWith	Union with another collection
$graphLookup	Recursive graph lookup
$redact	Restrict document content
$merge	Write results to a collection
$out	Write results to a collection (replace)
$setWindowFields	Window functions
$densify	Fill gaps in sequence
$fill	Fill missing values
$documents	Provide literal documents
$collStats	Collection statistics
$indexStats	Index statistics
$geoNear	Geospatial near query
$search	Atlas text search (basic substring support)
$searchMeta	Atlas search metadata (stub)
$vectorSearch	Vector similarity search (brute-force)

Group Accumulators

Accumulator	Description
$sum	Sum of values
$avg	Average of values
$min	Minimum value
$max	Maximum value
$first	First value in group
$last	Last value in group
$push	Array of all values
$addToSet	Array of unique values
$count	Count of documents
$mergeObjects	Merge documents
$stdDevPop	Population standard deviation
$stdDevSamp	Sample standard deviation
$top / $bottom	Top/bottom by sort
$topN / $bottomN	Top/bottom N by sort
$firstN / $lastN	First/last N values
$maxN / $minN	Max/min N values
$accumulator	Custom JavaScript accumulator (requires JsTriggers)

Window Functions

Available in $setWindowFields:

$sum, $avg, $min, $max, $count, $push, $addToSet, $first, $last, $stdDevPop, $stdDevSamp, $rank, $denseRank, $documentNumber, $shift, $expMovingAvg, $derivative, $integral, $covariancePop, $covarianceSamp, $linearFill, $locf

Expression Operators

Arithmetic (16)

$add, $subtract, $multiply, $divide, $mod, $abs, $ceil, $floor, $round, $trunc, $pow, $sqrt, $log, $log10, $ln, $exp

Trigonometric (9)

$sin, $cos, $tan, $asin, $acos, $atan, $atan2, $degreesToRadians, $radiansToDegrees

String (20)

$concat, $toLower, $toUpper, $trim, $ltrim, $rtrim, $substr, $substrBytes, $substrCP, $strLenBytes, $strLenCP, $indexOfBytes, $indexOfCP, $split, $strcasecmp, $replaceOne, $replaceAll, $regexMatch, $regexFind, $regexFindAll

Comparison (7)

$cmp, $eq, $ne, $gt, $gte, $lt, $lte

Conditional (3)

$cond, $ifNull, $switch

Logical (3)

$and, $or, $not

Array (17)

$arrayElemAt, $size, $isArray, $concatArrays, $in, $filter, $map, $reduce, $reverseArray, $range, $slice, $first, $last, $sortArray, $objectToArray, $arrayToObject, $zip

Type & Conversion (11)

$type, $convert, $toBool, $toInt, $toLong, $toDouble, $toDecimal, $toString, $toDate, $toObjectId, $isNumber

Date (14)

$year, $month, $dayOfMonth, $hour, $minute, $second, $millisecond, $dayOfWeek, $dayOfYear, $dateToString, $dateFromString, $dateAdd, $dateSubtract, $dateDiff

Object (3)

$mergeObjects, $getField, $setField

Special (8)

$literal, $let, $binarySize, $bsonSize, $rand, $sampleRate, $toHashedIndexKey, $function (requires JsTriggers)

Timestamp (2)

$tsIncrement, $tsSecond

See Also

• Filter & Update Operators — Query and update operators
• LINQ Support — LINQ-based querying
• Features — Full feature overview