aggregation framework - MongoDB $match inside $cond -

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consider following:

db.stores.aggregate(      { $project: {          _id: 0,          in_radius: {              $cond: {                  if: <geowithinexpression>,                  then: 1,                  else: 0              }         }     } })

geowithinexpression actually:

$match: {   location: {     $geowithin: {       $center: [[lat, lon], radius]     }   } }

i'm doing can use $group on result set counting number of stores in radius. (i'm using $project since want more custom columns 1 , return them in 1 time).

is possible?

this not possible number of reasons quite reasonable really.

  • while see trying achieve, basic premise $match identifier pipeline stage in , therefore can used way.

  • the second case here seem looking sort of "operator" return $geowithin type of result in logical (true/false) way used in $project or $group stage. falls on concept "geo-spatial" queries require index used, , reason place in aggregation pipeline can make use of index first stage, typically "should" $match stage.

as stated, concept quite reasonable @ no other time initial pipeline stage going have matches document on index created. new document "copies" exist within pipeline processing , therefore not have associated index.

while clear intention to "test" data locations within various sets, best approach use several queries , combine results in code or otherwise write out collection.


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