NdrParquet

Based on Ollie Tulloch's boilerplate MongoDB example, this generates parquet file(s) using NdrImport and Apache Arrow.

Installation

Add this line to your application's Gemfile:

gem 'ndr_parquet', git: 'https://github.com/timgentry/ndr_parquet', branch: 'main'

And then execute:

$ bundle install

Usage

Below is an example that extracts data from a spreadsheet and transforms it into to a raw and mapped parquet files, defined by their Hash "klass":

require 'ndr_parquet'

source_file = SafePath.new(...).join('ABC_Collection-June-2020_03.xlsm')
table_mappings = SafePath.new(...).join('national_collection.yml')
generator = NdrParquet::Generator.new(source_file, table_mappings)
generator.process

See test/ndr_parquet_test.rb for a more complete working example.

More information on the workings of the mapper are available in the wiki.

Type definitions

Columns are always cast as strings in raw parquet files. To specify a column type in the mapped parquet files, add arrow_data_type to field mappings. For example:

  - column: TotalNum
    mappings:
    - field: TOTAL_NUMBER
      arrow_data_type: :int32

defines an integer TOTAL_NUMBER column in the mapped parquet files, with values cast appropriately for that type.

Currently supported Arrow column types are:

• :binary
• :boolean
• :date32
• :decimal128, :decimal256
• :int8, :int16, :int32, :int64 and :integer
• :string [default]
• :uint8, :uint16, :uint32 and :uint64

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/timgentry/ndr_parquet. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the NdrParquet::Generator project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.