Add basic example program for connecting to CrateDB with Ruby

Author: amotl

by-language/ruby/.gitignore

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+Gemfile.lock

by-language/ruby/Gemfile

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+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'crate_ruby', '<1'
+gem 'pg', '<2'

by-language/ruby/README.rst

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+##################################################
+Basic examples for connecting to CrateDB with Ruby
+##################################################
+
+
+*****
+About
+*****
+
+This is a basic example program for connecting to CrateDB with Ruby.
+It uses the `crate_ruby`_ driver to connect to CrateDB using HTTP.
+It also demonstrates CrateDB's `PostgreSQL wire protocol`_ compatibility by
+exercising the same example using Ruby's canonical `pg`_ driver.
+
+For further information, please also visit the `CrateDB clients and tools`_ page.
+Because CrateDB only supports (implicitly created) `table schemas`_ instead of databases,
+it makes sense to also have a look at the `PostgreSQL documentation about schemas`_.
+
+
+*****
+Usage
+*****
+
+Run CrateDB::
+
+    docker run -it --rm --publish=4200:4200 --publish=5432:5432 crate:5.1.1
+
+Install example program::
+
+    git clone https://github.com/crate/cratedb-examples
+    cd cratedb-examples/by-language/ruby
+
+    gem install bundler
+    bundle install
+
+Invoke example program::
+
+    # Using `crate_ruby` driver.
+    ruby ruby_example.rb crate_ruby
+
+    # Using `pg` driver.
+    ruby ruby_example.rb pg
+
+
+.. _CrateDB clients and tools: https://crate.io/docs/crate/clients-tools/
+.. _crate_ruby: https://github.com/crate/crate_ruby
+.. _pg: https://rubygems.org/gems/pg
+.. _PostgreSQL documentation about schemas: https://www.postgresql.org/docs/current/ddl-schemas.html
+.. _PostgreSQL wire protocol: https://crate.io/docs/reference/en/latest/protocols/postgres.html
+.. _table schemas: https://crate.io/docs/crate/reference/en/latest/general/ddl/create-table.html#schemas

by-language/ruby/ruby_example.rb

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+#
+# Basic examples for connecting to CrateDB with Ruby, using both HTTP and PostgreSQL protocols.
+#
+# https://github.com/crate/cratedb-examples/tree/main/spikes/ruby-basic
+#
+
+def demo_crate_ruby
+
+  puts "=" * 42
+  puts "Demo using `crate_ruby` library"
+  puts "=" * 42
+
+  # Use `crate_ruby` library.
+  require 'crate_ruby'
+  client = CrateRuby::Client.new(servers = ["localhost:4200"], opts = {username: "crate"})
+
+  # Insert data.
+  client.execute("CREATE TABLE IF NOT EXISTS testdrive (id INT PRIMARY KEY, data TEXT);")
+  client.execute("DELETE FROM testdrive;")
+  client.execute("INSERT INTO testdrive VALUES (0, 'zero'), (1, 'one'), (2, 'two')")
+  client.execute("REFRESH TABLE testdrive;")
+
+  # Query data.
+  result = client.execute("SELECT * FROM testdrive ORDER BY id")
+
+  puts "Columns and values:"
+  p Columns: result.cols, Results: result.values
+  puts
+
+  puts "Results by row:"
+  result.each do |row|
+    puts row.inspect
+  end
+
+end
+
+
+def demo_pg
+
+  puts "=" * 42
+  puts "Demo using `pg` library"
+  puts "=" * 42
+
+  # Use `pg` library.
+  require 'pg'
+  client = PG.connect("postgresql://crate@localhost:5432/doc")
+
+  # Insert data.
+  client.exec("CREATE TABLE IF NOT EXISTS testdrive (id INT PRIMARY KEY, data TEXT);")
+  client.exec("DELETE FROM testdrive;")
+  client.exec("INSERT INTO testdrive VALUES (0, 'zero'), (1, 'one'), (2, 'two')")
+  client.exec("REFRESH TABLE testdrive;")
+
+  # Query data.
+  result = client.exec("SELECT * FROM testdrive ORDER BY id")
+
+  puts "Columns and values:"
+  p Columns: result.fields, Results: result.values
+  puts
+
+  puts "Results by row:"
+  result.each do |row|
+    puts row.inspect
+  end
+
+end
+
+
+if __FILE__ == $0
+  driver = ARGV[0]
+  if driver == "crate_ruby"
+    demo_crate_ruby()
+  elsif driver == "pg"
+    demo_pg()
+  else
+    raise "Unknown driver: #{driver}. Please use 'crate_ruby' or 'pg'."
+  end
+end