Module: ObjectTable::Joining::ClassMethods

Included in:
ObjectTable
Defined in:
lib/object_table/joining.rb

Instance Method Summary collapse

Instance Method Details

#join(left, right, *keys, type: 'inner') ⇒ Object

-1 in an index indicates a missing value



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# File 'lib/object_table/joining.rb', line 13

def join(left, right, *keys, type: 'inner')
  incl_left = incl_right = false
  case type
  when 'left' then incl_left = true
  when 'right' then incl_right = true
  when 'outer' then incl_left = incl_right = true
  when 'inner'
  else raise "Expected one of (inner, left, outer, right), got #{type.inspect}"
  end

  lkeys = Util.get_rows(left, keys)
  rkeys = Util.get_rows(right, keys)

  rgroups = Util.group_indices(rkeys)
  rgroups.default = (incl_left ? [-1] : []) # keep left missing values if incl_left

  lindex = rgroups.values_at(*lkeys)
  rindex = lindex.flatten
  lindex = lindex.each_with_index.flat_map{|r, i| r.fill(i)}

  if incl_right
    # rindex may have missing values
    # so add a dud value at the end ...
    missing = NArray.int(right.nrows + 1).fill!(1)
    missing[rindex] = 0
    missing[-1] = 0 # ... that we always exclude
    missing = missing.where
    rindex.concat( missing.to_a )
    lindex.concat( Array.new(missing.length, -1) )
  end

  index = [lindex, rindex].map{|ix| NArray.to_na(ix)}
  blanks = index.map{|ix| ix.eq(-1).where}

  colnames = [left.colnames, right.colnames - left.colnames]
  data = [left, right].zip(index, blanks).zip(colnames).flat_map do |args, cols|
    cols.map{|k| [k, Joining.copy_column(k, *args)] }
  end

  table = __table_cls__.new(data)
  if incl_right
    keys.each do |k|
      table[k][false, blanks[0]] = right[k][false, missing]
    end
  end

  table
end