Class: Parse::GroupBy

Inherits:
Object
  • Object
show all
Defined in:
lib/parse/query.rb

Overview

Helper class for handling group_by aggregations with method chaining. Supports count, sum, average, min, max operations on grouped data. Can optionally flatten array fields before grouping to count individual array elements.

Direct Known Subclasses

SortableGroupBy

Instance Method Summary collapse

Constructor Details

#initialize(query, group_field, flatten_arrays: false, return_pointers: false, mongo_direct: false) ⇒ GroupBy

Returns a new instance of GroupBy.

Parameters:

  • query (Parse::Query) —

    the base query to group

  • group_field (Symbol, String) —

    the field to group by

  • flatten_arrays (Boolean) (defaults to: false) —

    whether to flatten array fields before grouping

  • return_pointers (Boolean) (defaults to: false) —

    whether to return Parse::Pointer objects for pointer values

  • mongo_direct (Boolean) (defaults to: false) —

    whether to query MongoDB directly bypassing Parse Server



6213
6214
6215
6216
6217
6218
6219
6220
6221
 
# File 'lib/parse/query.rb', line 6213

def initialize(query, group_field, flatten_arrays: false, return_pointers: false, mongo_direct: false)
  @query = query
  @group_field = group_field
  @flatten_arrays = flatten_arrays
  @return_pointers = return_pointers
  @mongo_direct = mongo_direct
  @sort_target = nil    # nil | :key | :value | :size
  @sort_direction = nil # :asc | :desc
end

Instance Method Details

#average(field) ⇒ Hash Also known as: avg

Calculate average of a field for each group.

Examples:

Document.group_by(:category).average(:duration)
# => {"video" => 120.5, "audio" => 45.2}

Parameters:

  • field (Symbol, String) —

    the field to average within each group.

Returns:

  • (Hash) —

    a hash with group values as keys and averages as values.



6433
6434
6435
6436
6437
6438
6439
6440
 
# File 'lib/parse/query.rb', line 6433

def average(field)
  if field.nil? || !field.respond_to?(:to_s)
    raise ArgumentError, "Invalid field name passed to `average`."
  end

  formatted_field = @query.send(:format_aggregation_field, field)
  execute_group_aggregation("average", { "$avg" => "$#{formatted_field}" })
end

#count ⇒ Hash

Count the number of items in each group.

Examples:

Document.group_by(:category).count
# => {"image" => 45, "video" => 23, "audio" => 12}

Returns:

  • (Hash) —

    a hash with group values as keys and counts as values.



6408
6409
6410
 
# File 'lib/parse/query.rb', line 6408

def count
  execute_group_aggregation("count", { "$sum" => 1 })
end

#list ⇒ Hash{Object => Array<Parse::Object>}

Note:

On the Parse REST /aggregate path there is no ACL/CLP/protectedFields enforcement — that endpoint is master-key-only. On the mongo-direct path the SDK's ACL $match runs before $group, and both ACL redaction and protectedFields stripping recurse into pushed arrays, so scoped agents get correctly filtered records. The Array recursion that makes this safe lives in Parse::ACLScope#redact_subdocs! (lib/parse/acl_scope.rb) and Parse::CLPScope#walk_and_delete! (lib/parse/clp_scope.rb); if you change either of those, re-verify .list still strips correctly.

Collect every document of each group into an array of Parse::Object instances. Implemented as $push: "$$ROOT", so each group's value is the full set of underlying records (subject to the query's where constraints).

Use this when you want the actual records per group, not just an aggregated scalar. Combine with .order(size: :desc) to surface the largest groups first.

Examples:

Document.where(:status => "active").group_by(:category).list
# => {"image" => [<Document:...>, <Document:...>], "video" => [<Document:...>]}

Largest groups first

Document.group_by(:category).order(size: :desc).list

Returns:



6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
6508
6509
6510
6511
6512
 
# File 'lib/parse/query.rb', line 6492

def list
  table = @query.instance_variable_get(:@table)
  # `$push: "$$ROOT"` pushes the raw MongoDB-storage-format document
  # into the result array on BOTH the REST and mongo-direct paths —
  # Parse Server's aggregate envelope only rewrites the outermost row's
  # `_id` to `objectId`, not nested arrays. So `_id`, `_p_<field>`
  # pointer strings, `_acl`/`_rperm`/`_wperm`, and `_created_at`/
  # `_updated_at` all survive into the pushed docs and have to be
  # normalized to Parse shape before `Parse::Object.build` will produce
  # an instance with the right id, associations, ACL, and timestamps.
  require_relative "mongodb"
  build_object = lambda do |doc|
    parse_doc = Parse::MongoDB.convert_document_to_parse(doc, table)
    parse_doc ? Parse::Object.build(parse_doc, table) : nil
  end

  execute_group_aggregation("list", { "$push" => "$$ROOT" }) do |docs|
    next [] unless docs.is_a?(Array)
    docs.map(&build_object).compact
  end
end

#max(field) ⇒ Hash

Find maximum value of a field for each group.

Parameters:

  • field (Symbol, String) —

    the field to find maximum for within each group.

Returns:

  • (Hash) —

    a hash with group values as keys and maximum values as values.



6459
6460
6461
6462
6463
6464
6465
6466
 
# File 'lib/parse/query.rb', line 6459

def max(field)
  if field.nil? || !field.respond_to?(:to_s)
    raise ArgumentError, "Invalid field name passed to `max`."
  end

  formatted_field = @query.send(:format_aggregation_field, field)
  execute_group_aggregation("max", { "$max" => "$#{formatted_field}" })
end

#min(field) ⇒ Hash

Find minimum value of a field for each group.

Parameters:

  • field (Symbol, String) —

    the field to find minimum for within each group.

Returns:

  • (Hash) —

    a hash with group values as keys and minimum values as values.



6447
6448
6449
6450
6451
6452
6453
6454
 
# File 'lib/parse/query.rb', line 6447

def min(field)
  if field.nil? || !field.respond_to?(:to_s)
    raise ArgumentError, "Invalid field name passed to `min`."
  end

  formatted_field = @query.send(:format_aggregation_field, field)
  execute_group_aggregation("min", { "$min" => "$#{formatted_field}" })
end

#order(spec) ⇒ self

Order grouped results by the group key, the aggregated value, or (for #list) the size of the per-group array. The ordering is pushed down into the aggregation pipeline as a $sort stage (plus a $addFields helper for :size), so MongoDB does the sort and the returned Hash preserves the order via Ruby's insertion semantics.

Examples:

Biggest groups first

Document.group_by(:category).order(value: :desc).count

Alphabetical group keys

Document.group_by(:category).order(key: :asc).count

Groups with the most members first

Document.group_by(:category).order(size: :desc).list

Parameters:

  • spec (Hash, Symbol) —

    one of:

    • { key: :asc | :desc } — sort by the group key
    • { value: :asc | :desc } — sort by the aggregated value (count/sum/avg/min/max)
    • { size: :asc | :desc } — sort by the length of the pushed array (only meaningful with #list)
    • :asc or :desc — shorthand for { key: direction }, matching Ruby's Hash#sort default of sorting by key.

Returns:

  • (self) 


6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
 
# File 'lib/parse/query.rb', line 6244

def order(spec)
  target, direction =
    case spec
    when Symbol
      [:key, spec]
    when Hash
      unless spec.size == 1
        raise ArgumentError, "order(...) expects a single pair, e.g. {value: :desc} (got #{spec.inspect})"
      end
      k, v = spec.first
      [k.to_sym, v.to_sym]
    else
      raise ArgumentError, "order(...) expects {key:|value:|size: => :asc|:desc} or :asc/:desc (got #{spec.inspect})"
    end

  unless %i[key value size].include?(target)
    raise ArgumentError, "order(...) target must be :key, :value, or :size (got #{target.inspect})"
  end
  unless %i[asc desc].include?(direction)
    raise ArgumentError, "order(...) direction must be :asc or :desc (got #{direction.inspect})"
  end

  @sort_target = target
  @sort_direction = direction
  self
end

#pipeline ⇒ Array<Hash>

Returns the MongoDB aggregation pipeline that would be used for a count operation. This is useful for debugging and understanding the generated pipeline.

Examples:

Post.where(:author_workspace.eq => workspace).group_by(:last_action).pipeline
# => [{"$match"=>{"authorWorkspace"=>"Workspace$abc123"}}, {"$group"=>{"_id"=>"$lastAction", "count"=>{"$sum"=>1}}}, {"$project"=>{"_id"=>0, "objectId"=>"$_id", "count"=>1}}]

Returns:

  • (Array<Hash>) —

    the MongoDB aggregation pipeline



6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
 
# File 'lib/parse/query.rb', line 6296

def pipeline
  # This introspection builds the same shape as the count execution
  # path (`$sum: 1`), so reject order/aggregation combinations that
  # the count path would reject at runtime — otherwise the preview
  # silently produces a pipeline the SDK would never actually run.
  validate_sort_target_for_operation!("count")

  # Format the group field name
  formatted_group_field = @query.send(:format_aggregation_field, @group_field)

  # Build the aggregation pipeline (same logic as execute_group_aggregation)
  pipeline = []

  # Add match stage if there are where conditions. `compile_where`
  # is already marker-free; use `compile_markers` to extract
  # __aggregation_pipeline stages.
  compiled_where = @query.send(:compile_where)
  markers = @query.send(:compile_markers)
  if compiled_where.present? || markers.key?("__aggregation_pipeline")
    # Collect all match conditions to merge into a single $match stage
    match_conditions = []
    non_match_stages = []

    # `compiled_where` is marker-free already.
    regular_constraints = compiled_where
    if regular_constraints.present?
      aggregation_where = @query.send(:convert_constraints_for_aggregation, regular_constraints)
      stringified_where = @query.send(:convert_dates_for_aggregation, aggregation_where)
      match_conditions << stringified_where
    end

    # Extract aggregation pipeline stages and merge $match stages
    if markers.key?("__aggregation_pipeline")
      markers["__aggregation_pipeline"].each do |stage|
        if stage.is_a?(Hash) && stage.key?("$match")
          # Extract the $match condition for merging
          match_conditions << stage["$match"]
        else
          # Non-$match stages go directly to pipeline
          non_match_stages << stage
        end
      end
    end

    # Combine all match conditions into a single $match stage
    if match_conditions.any?
      if match_conditions.length == 1
        pipeline << { "$match" => match_conditions.first }
      else
        # Use $and to combine multiple match conditions
        pipeline << { "$match" => { "$and" => match_conditions } }
      end
    end

    # Add any non-$match stages from the aggregation pipeline
    pipeline.concat(non_match_stages)
  end

  # Add unwind stage if flatten_arrays is enabled
  if @flatten_arrays
    pipeline << { "$unwind" => "$#{formatted_group_field}" }
  end

  # Add group stage (using count as example aggregation)
  pipeline << {
    "$group" => {
      "_id" => "$#{formatted_group_field}",
      "count" => { "$sum" => 1 },
    },
  }

  # Add $addFields + $sort stages if ordering was configured. Sort happens
  # before $project so we can reference `_id` (pre-rename) for :key sorts.
  add_fields = size_addfields_stage
  pipeline << add_fields if add_fields
  sort = sort_stage
  pipeline << sort if sort

  pipeline << {
    "$project" => {
      "_id" => 0,
      "objectId" => "$_id",
      "count" => 1,
    },
  }

  pipeline
end

#raw(operation, aggregation_expr) ⇒ Array<Hash>

Returns raw unprocessed aggregation results

Parameters:

  • operation (String) —

    the aggregation operation

  • aggregation_expr (Hash) —

    the MongoDB aggregation expression

Returns:



6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
 
# File 'lib/parse/query.rb', line 6389

def raw(operation, aggregation_expr)
  formatted_group_field = @query.send(:format_aggregation_field, @group_field)
  pipeline = build_pipeline(formatted_group_field, aggregation_expr)

  response = @query.client.aggregate_pipeline(
    @query.instance_variable_get(:@table),
    pipeline,
    headers: {},
    **@query.send(:_opts),
  )

  response.result || []
end

#sort(direction = :asc) ⇒ self

Sort grouped results by the group key. Alias for order(key: direction), mirroring Ruby's Hash#sort default. For value-based ordering use #order explicitly (e.g. .order(value: :desc)).

Note the asymmetry with chaining: .sort.count pushes the sort into the aggregation pipeline and returns a Hash keyed by group, while .count.sort first materializes the Hash and then calls Hash#sort, which returns an Array<[key, value]>. Both order by key ascending by default; this method exists so the pipeline form is also available.

Examples:

Document.group_by(:category).sort.count        # group keys ascending
Document.group_by(:category).sort(:desc).count # group keys descending

Parameters:

  • direction (Symbol) (defaults to: :asc) —

    :asc (default) or :desc

Returns:

  • (self) 


6286
6287
6288
 
# File 'lib/parse/query.rb', line 6286

def sort(direction = :asc)
  order(direction)
end

#sum(field) ⇒ Hash

Sum a field for each group.

Examples:

Document.group_by(:project).sum(:file_size)
# => {"Project1" => 1024000, "Project2" => 512000}

Parameters:

  • field (Symbol, String) —

    the field to sum within each group.

Returns:

  • (Hash) —

    a hash with group values as keys and sums as values.



6418
6419
6420
6421
6422
6423
6424
6425
 
# File 'lib/parse/query.rb', line 6418

def sum(field)
  if field.nil? || !field.respond_to?(:to_s)
    raise ArgumentError, "Invalid field name passed to `sum`."
  end

  formatted_field = @query.send(:format_aggregation_field, field)
  execute_group_aggregation("sum", { "$sum" => "$#{formatted_field}" })
end