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4805 :: Nimongo comparison (i.e. $gt) queries

• rustomax (orginal) [2019-04-23T17:25:21+02:00] view original

  I can't figure out how to do comparison queries with Nimongo. Would appreciate any solutions.

  import oids
  
  import nimongo/bson  ## MongoDB BSON serialization/deserialization
  import nimongo/mongo ## MongoDB client
  
  ## Create new Mongo client
  var m = newMongo()
  
  ## Connect to Mongo server
  let connectResult = m.connect()
  
  ## Specify collection
  let collection = m["db"]["weather"]
  
  ## Create new bson document
  let weather_item = %*{
    "_id": $genOid(),
    "temp": 15.6,
    "feels_like": 14.5,
    "units": "C"
  }
  
  ## Insert document into DB
  collection.insert(weather_item)
  
  ## Fetch number of weather items
  let num_wi = collection.find(%*{}).count()
  echo "# of weather items: ", num_wi
  
  # tried different variations of the query below, but still can't get the correct behavior
  let query = B("temp", "{$gt:10}".toBson)
  echo query
  
  let temps_over_10C = collection.find(query)
  let tn = temps_over_10C.count()
  
  echo "Found ", tn, " records with temp over 10C"
  for temp in temps_over_10C:
    echo "temp = ", temp
  
  # Output:
  # # of weather items: 4
  # {
  #     "temp" : "{$gt:10}"
  # }
  # Found 0 records with temp over 10C
  Run

  The records are correctly inserted into mongo (from multiple runs). And I am confident the find syntax is correct as the same command works from the mongo shell:

  
  > db.weather.find({"temp": {$gt:10}})
  { "_id" : "5cbf2625e269b85d096176b6", "temp" : 15.6, "feels_like" : 14.5, "units" : "C" }
  { "_id" : "5cbf299d4fded4440a4531fe", "temp" : 15.6, "feels_like" : 14.5, "units" : "C" }
  Run

  I suspect it has to do with additional double quotes being inserted into the filter, but I am not sure how to force nimongo to do without them:

  
  > db.weather.find({"temp": "{$gt:10}"}).count()
  0
  Run

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• mashingan (orginal) [2019-04-24T02:31:29+02:00] view original

  "{$gt:10}".toBson

  This is string, not bson embedded object, what you need is

  let query = %{
      "temp": {
          "$gt": 10
      }
  }
  Run

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• rustomax (orginal) [2019-04-24T05:13:29+02:00] view original

  @mashingan, thank you! Works like a charm with a minor tweak (needs the star *):

  let query = %*{"temp": {"$gt": 10}}
  Run

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