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+<!---
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# Red Gandiva - Gandiva Ruby
+
+Red Gandiva is the Ruby bindings of Gandiva. Red Gandiva is based on GObject Introspection.
+
+Gandiva is a toolset for compiling and evaluating expressions on Arrow data.
+
+[GObject Introspection](https://wiki.gnome.org/action/show/Projects/GObjectIntrospection) is a middleware for language bindings of C library. GObject Introspection can generate language bindings automatically at runtime.
+
+Red Gandiva uses [Gandiva GLib](https://github.com/apache/arrow/tree/master/c_glib/gandiva-glib) and [gobject-introspection gem](https://rubygems.org/gems/gobject-introspection) to generate Ruby bindings of Gandiva.
+
+Gandiva GLib is a C wrapper for [Gandiva C++](https://github.com/apache/arrow/tree/master/cpp/gandiva). GObject Introspection can't use Gandiva C++ directly. Gandiva GLib is a bridge between Gandiva C++ and GObject Introspection.
+
+gobject-introspection gem is a Ruby bindings of GObject Introspection. Red Gandiva uses GObject Introspection via gobject-introspection gem.
+
+## Install
+
+Install Gandiva GLib before install Red Gandiva. See [Apache Arrow install document](https://arrow.apache.org/install/) for details.
+
+Install Red Gandiva after you install Gandiva GLib:
+
+```text
+% gem install red-gandiva
+```
+
+## Usage
+
+```ruby
+require "gandiva"
+
+table = Arrow::Table.new(:field1 => Arrow::Int32Array.new([1, 2, 3, 4]),
+                         :field2 => Arrow::Int32Array.new([11, 13, 15, 17]))
+schema = table.schema
+
+expression1 = schema.build_expression do |record|
+  record.field1 + record.field2
+end
+
+expression2 = schema.build_expression do |record, context|
+  context.if(record.field1 > record.field2)
+    .then(record.field1 / record.field2)
+    .else(record.field1)
+end
+
+projector = Gandiva::Projector.new(schema, [expression1, expression2])
+table.each_record_batch do |record_batch|
+  outputs = projector.evaluate(record_batch)
+  puts outputs.collect(&:values))
+end
+```