Using Aggregation Operators

1. Using Arithmetic Operators

Operator	Effect
$add, $subtract, $multiply, $divide, $mod	Basic math
$abs, $ceil, $floor, $round, $trunc	Rounding
$pow, $sqrt, $exp, $ln, $log, $log10	Power/log
$sin, $cos, $tan, $asin, $acos, $atan, $atan2	Trig

Operator	Returns
$eq, $ne, $gt, $gte, $lt, $lte	Boolean
$cmp	-1 / 0 / 1

Operator	Effect
$concat	Concatenate
$substr, $substrBytes, $substrCP	Substring
$toLower, $toUpper	Case
$trim, $ltrim, $rtrim	Whitespace
$split	Split by separator
$strLenBytes, $strLenCP	Length
$indexOfBytes, $indexOfCP	Search
$regexMatch, $regexFind, $regexFindAll	Regex
$replaceOne, $replaceAll	Replace

Operator	Effect
$year, $month, $dayOfMonth, $hour, $minute, $second, $millisecond	Extract
$dayOfWeek, $dayOfYear, $week	Calendar
$dateAdd, $dateSubtract	Add/subtract intervals
$dateDiff	Difference in unit
$dateToString	Format
$dateFromString	Parse
$dateTrunc	Bucket to unit

Operator	Use
$sum, $avg, $min, $max	Stats
$push	Collect to array
$addToSet	Unique collect
$first, $last	Boundary doc
$mergeObjects	Merge subdocs
$stdDevPop, $stdDevSamp	Std deviation
$accumulator	Custom JS accumulator
$count	Per-group count (5.0+)
$topN, $bottomN, $firstN, $lastN, $minN, $maxN	Top-N (5.2+)

Operator	Effect
$toString, $toInt, $toLong, $toDouble, $toDecimal	Numeric/string conversions
$toDate, $toObjectId, $toBool	Type conversion
$convert	Generic with onError / onNull
$type	Return BSON type string

Operator	Effect
$setUnion	Union
$setIntersection	Intersect
$setDifference	Difference
$setEquals	Equal as sets
$setIsSubset	Subset?
$anyElementTrue / $allElementsTrue	Truthiness

Stage	Detail
$setWindowFields	partitionBy, sortBy, output with window
Window	documents:[N,M] or range:[low,high,unit]
Operators	$sum, $avg, $rank, $denseRank, $rowNumber, $shift, $derivative, $integral, $covarianceSamp, $expMovingAvg, $linearFill, $locf

{ $setWindowFields: {
    partitionBy: "$symbol",
    sortBy: { ts: 1 },
    output: { ma7: { $avg: "$price", window: { documents: [-6, 0] } } }
} }