JSON compressor example for me-redis gem

json_compressor.rb

module RSmazCompressor
  def self.compress(value); RSmaz.compress(value) end
  def self.decompress(value); RSmaz.decompress(value) end
end

module ZLibJSONCompressor
  def self.compress(value); Zlib.deflate(value.to_json) end
  def self.decompress(value); JSON.load( Zlib.inflate( value ) )end
end

# Active record object compressor, but idea is may be used on any object with json representation 
module ActiveRecordJSONCompressor
  # this is the example, automated for simplicity, if DB schema changes, than cache may broke!!
  # in reallife scenario either invalidate cache, or use explicit schemas
  # like User: { first_name: 1, last_name: 2 ... }, than your cache will be safer on schema changes.
  COMPRESSOR_SCHEMAS = [User, HTag].map{|mdl|
    [mdl.to_s, mdl.column_names.each_with_index.map{ |el, i| [el, (20 + i).to_base62] }.to_h]
  }.to_h.with_indifferent_access

  REVERSE_COMPRESSOR_SCHEMA = COMPRESSOR_SCHEMAS.dup.transform_values(&:invert)

  def self.compress( object )
    use_schema = COMPRESSOR_SCHEMAS[object.class.to_s]
    # _s - shorten for schema, s cannot be used since its a number in Base62 system
    Zlib.deflate(
        object.serializable_hash
            .slice( *use_schema.keys )
            .transform_keys{ |k| use_schema[k] }
            .reject{ |_,v| v.blank? }
            .merge!( _s: object.class.to_s ).to_json
    )
  end

  def self.decompress(value)
    compressed_hash = JSON.load( Zlib.inflate(value) )
    model = compressed_hash.delete('_s')
    schema = REVERSE_COMPRESSOR_SCHEMA[model]
    model.constantize.new( compressed_hash.transform_keys{ |k| schema[k] } )
  end
end