Description

The documentation for $bucketAuto found here: https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/

 

States: "The document for each bucket contains an _id field, whose value specifies the inclusive lower bound and the exclusive upper bound for the bucket..."

 

The problem is that for the last bucket, the max value in the id field is inclusive.

 

The example on your page shows this to be the case:

 

Using these documents:

 

{ "_id" : 1, "title" : "The Pillars of Society", "artist" : "Grosz", "year" : 1926,     "price" : NumberDecimal("199.99"),     "dimensions" : \{ "height" : 39, "width" : 21, "units" : "in" }

}

{ "_id" : 2, "title" : "Melancholy III", "artist" : "Munch", "year" : 1902,     "price" : NumberDecimal("280.00"),     "dimensions" : \{ "height" : 49, "width" : 32, "units" : "in" }

}

{ "_id" : 3, "title" : "Dancer", "artist" : "Miro", "year" : 1925,     "price" : NumberDecimal("76.04"),     "dimensions" : \{ "height" : 25, "width" : 20, "units" : "in" }

}

{ "_id" : 4, "title" : "The Great Wave off Kanagawa", "artist" : "Hokusai",     "price" : NumberDecimal("167.30"),     "dimensions" : \{ "height" : 24, "width" : 36, "units" : "in" }

}

{ "_id" : 5, "title" : "The Persistence of Memory", "artist" : "Dali", "year" : 1931,     "price" : NumberDecimal("483.00"),     "dimensions" : \{ "height" : 20, "width" : 24, "units" : "in" }

}

{ "_id" : 6, "title" : "Composition VII", "artist" : "Kandinsky", "year" : 1913,     "price" : NumberDecimal("385.00"),     "dimensions" : \{ "height" : 30, "width" : 46, "units" : "in" }

}

{ "_id" : 7, "title" : "The Scream", "artist" : "Munch",     "price" : NumberDecimal("159.00"),     "dimensions" : \{ "height" : 24, "width" : 18, "units" : "in" }

}

{ "_id" : 8, "title" : "Blue Flower", "artist" : "O'Keefe", "year" : 1918,     "price" : NumberDecimal("118.42"),     "dimensions" : \{ "height" : 24, "width" : 20, "units" : "in" }

}

 

With this pipeline:

 

db.artwork.aggregate( [

   {

     $bucketAuto:

{          groupBy: "$price",          buckets: 4      }

   }

] )

 

Produces these four buckets:

 

{

  "_id" :

{     "min" : NumberDecimal("76.04"),     "max" : NumberDecimal("159.00")   }

,

  "count" : 2

}

{

  "_id" :

{     "min" : NumberDecimal("159.00"),     "max" : NumberDecimal("199.99")   }

,

  "count" : 2

}

{

  "_id" :

{     "min" : NumberDecimal("199.99"),     "max" : NumberDecimal("385.00")   }

,

  "count" : 2

}

{

  "_id" :

{     "min" : NumberDecimal("385.00"),     "max" : NumberDecimal("483.00")   }

,

  "count" : 2

}

 

Notice how the max of the last bucket matches the highest price document.

 

We ask that the documentation be updated to confirm that this is the correct behavior as right now it appears to be a bug since the documentation states the max id is suppose to be exclusive.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)