docs/source/ruby/index.rst

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====
Ruby
====

**red-adbc** is the Ruby binding for ADBC, built on top of ADBC GLib.
It is distributed as the `red-adbc gem on RubyGems
<https://rubygems.org/gems/red-adbc>`__.

Here we'll briefly tour basic features of ADBC with Ruby using the SQLite driver.

Installation
============

``red-adbc`` depends on the native Arrow GLib and ADBC GLib libraries. The
`rubygems-requirements-system
<https://rubygems.org/gems/rubygems-requirements-system>`__ plugin installs
these system dependencies automatically using your system package manager, so
install it first.

With ``gem``:

.. code-block:: shell

   gem install rubygems-requirements-system
   gem install red-adbc

Or, with Bundler, add the plugin and the gem to your ``Gemfile``:

.. code-block:: ruby

   source "https://rubygems.org"

   plugin "rubygems-requirements-system"

   gem "red-adbc"

Installing Drivers
------------------

You also need a driver for the database you want to connect to. See
:ref:`driver-table-install` for instructions. For the example below, you could
install `dbc <https://docs.columnar.tech/dbc>`__ and then install the SQLite
driver with:

.. code-block:: shell

   dbc install sqlite

Creating a Connection
=====================

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory") do |database|
     database.connect do |connection|
       # Use connection
     end
   end

In application code, the database and connection must be closed after usage or
memory may leak. Both ``Database.open`` and ``database.connect`` accept blocks
to accomplish this automatically.

Executing a Query
=================

We can execute a query and get the results as an Arrow table:

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory:") do |database|
     database.connect do |connection|
       table, = connection.query("SELECT 1, 2.0, 'Hello, world!'")
       puts table
     end
   end

Output:

.. code-block:: text

      1  2.0  'Hello, world!'
      (int64)  (double)  (utf8)
   0  1  2.0  Hello, world!

Ingesting Bulk Data
===================

We can insert a table of Arrow data into a new database table:

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory:") do |database|
     database.connect do |connection|
       # Create an Arrow table
       table = Arrow::Table.new(
         ints: Arrow::Int64Array.new([1, 2]),
         strs: Arrow::StringArray.new(["a", nil])
       )

       # Ingest into database
       connection.ingest("sample", table, mode: :create)

       # Query the data
       result, = connection.query("SELECT COUNT(DISTINCT ints) FROM sample")
       puts result
     end
   end

We can also append to an existing table:

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory:") do |database|
     database.connect do |connection|
       # Create initial table
       table = Arrow::Table.new(
         ints: Arrow::Int64Array.new([1, 2]),
         strs: Arrow::StringArray.new(["a", nil])
       )
       connection.ingest("sample", table, mode: :create)

       # Append more data
       table2 = Arrow::Table.new(
         ints: Arrow::Int64Array.new([2, 3]),
         strs: Arrow::StringArray.new([nil, "c"])
       )
       connection.ingest("sample", table2, mode: :append)

       # Query the combined data
       result, = connection.query("SELECT COUNT(DISTINCT ints) FROM sample")
       puts result
     end
   end

The ``mode`` parameter can be:

- ``:create`` - Create a new table (default)
- ``:append`` - Append to an existing table
- ``:replace`` - Replace an existing table

Getting Database/Driver Metadata
=================================

We can get information about the driver and the database:

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory:") do |database|
     database.connect do |connection|
       info = connection.info
       puts "Vendor: #{info[:vendor_name]}"
       puts "Driver: #{info[:driver_name]}"
     end
   end

We can also query for tables and columns in the database. This gives
a nested structure describing all the catalogs, schemas, tables, and
columns:

.. code-block:: ruby

   require "adbc"

   ADBC::Database.open(driver: "sqlite",
                       uri: ":memory:") do |database|
     database.connect do |connection|
       # Create a sample table first
       connection.query("CREATE TEMPORARY TABLE sample (ints INTEGER, strs TEXT)")

       # Get database objects
       objects = connection.get_objects(depth: :all)
       catalog = objects.raw_records[1]
       schema = catalog[1][0]
       tables = schema["db_schema_tables"]

       puts "Table: #{tables[0]["table_name"]}"
       columns = tables[0]["table_columns"]
       puts "Columns: #{columns.map { |c| c["column_name"] }.join(", ")}"
     end
   end

Next Steps
==========

- See the :doc:`drivers </driver/index>` to see which databases are supported
- Explore more examples in the `adbc-quickstarts repository <https://github.com/columnar-tech/adbc-quickstarts/tree/main/ruby>`_
- Explore the `Ruby source code <https://github.com/apache/arrow-adbc/tree/main/ruby>`_ for additional examples