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  1. Mongoid
  2. MONGOID-4414

Regression when searching in array field

    • Type: Icon: Bug Bug
    • Resolution: Works as Designed
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 5.0.0, 5.2.0
    • Component/s: None
    • Environment:
      Ubuntu Linux 16.04, Ruby 2.3, Rails 4.2, MongoDB 3.2

      I know I am a little late, but have only recently upgraded to Mongo 3.2 and mongoid 5. My users reported that one of search queries takes a lot of time.

      The query is on Array field which is filed with strings and indexed.
      field :search_a, type: Array
      index search_a: 1

      Collection holds about 200000 documents and search_a field is filed with words splited from name field. Query line is:
      self.where(search_a: /^#


      /, active: true)

      I first thought that the problem is MongoDB but when I tryed with mongoid 4.0.2 the problem was gone. Here is debug from rails console:
      Mongoid 4.0.2


      MOPED: COMMAND database=portal_development command={:count=>"reg_registers", :query=>{"search_a"=>/^avtomobil/, "active"=>true}} runtime: 3.8295ms
      MOPED: QUERY database=portal_development collection=reg_registers selector={"search_a"=>/^avtomobil/, "active"=>true} flags=[] limit=30 skip=0 batch_size=nil fields=nil runtime: 29.1166ms

      Mongoid 5.0.0
      Parameters: {"search"=>"avtomobil"}

      D, 2017-02-17T11:50:25.275855 #2134 DEBUG – : MONGODB | | portal_development.count | STARTED | {"count"=>"reg_registers", "query"=>{"search_a"=>/^avtomobil/, "active"=>true}}
      D, 2017-02-17T11:50:27.532941 #2134 DEBUG – : MONGODB | | portal_development.count | SUCCEEDED | 2.256757491s
      D, 2017-02-17T11:50:27.534074 #2134 DEBUG – : MONGODB | | portal_development.find | STARTED | {"find"=>"reg_registers", "filter"=>

      {"search_a"=>/^avtomobil/, "active"=>true}

      , "limit"=>30}

      Similar Mongoid 5.2.0
      As you can see query time has gone from few miliseconds to couple of seconds.

      I could not test last mongoid since it depends on rails 5.


            emily.stolfo Emily Stolfo
            d_rems@yahoo.com Damjan Rems
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