diff --git a/Gemfile b/Gemfile
index e4021ce8..6676ece7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,6 @@
-source 'https://rubygems.org/'
+source "https://rubygems.org/"
 gemspec
 
 group :development, :test do
-  gem 'tiny-presto', "~> 0.0.8"
+  gem "tiny-presto", "~> 0.0.8"
 end
diff --git a/Rakefile b/Rakefile
index 3b3e0bee..cd140115 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,22 +1,22 @@
 #!/usr/bin/env rake
-require 'bundler/gem_tasks'
+require "bundler/gem_tasks"
 
-require 'rake/testtask'
-require 'rake/clean'
+require "rake/testtask"
+require "rake/clean"
 
-require 'rspec/core/rake_task'
+require "rspec/core/rake_task"
 
 RSpec::Core::RakeTask.new(:spec)
 
-task :default => [:spec, :build]
+task default: [:spec, :build]
 
 GEN_MODEL_VERSIONS = %w[
   351
 ]
 
 namespace "modelgen" do
-  task :latest => :all do
-    require 'erb'
+  task latest: :all do
+    require "erb"
     erb = ERB.new(File.read("modelgen/models.rb"))
     @versions = GEN_MODEL_VERSIONS
     @latest_version = GEN_MODEL_VERSIONS.last
@@ -24,7 +24,7 @@ namespace "modelgen" do
     File.write("lib/trino/client/models.rb", data)
   end
 
-  task :all => GEN_MODEL_VERSIONS
+  task all: GEN_MODEL_VERSIONS
 
   GEN_MODEL_VERSIONS.each do |ver|
     file "build/trino-#{ver}.tar.gz" do
@@ -42,4 +42,3 @@ namespace "modelgen" do
     task ver => "lib/trino/client/model_versions/#{ver}.rb"
   end
 end
-
diff --git a/lib/trino-client.rb b/lib/trino-client.rb
index d668fbfb..c20fd856 100644
--- a/lib/trino-client.rb
+++ b/lib/trino-client.rb
@@ -1 +1 @@
-require 'trino/client'
+require "trino/client"
diff --git a/lib/trino/client.rb b/lib/trino/client.rb
index dfcb56b6..827b9593 100644
--- a/lib/trino/client.rb
+++ b/lib/trino/client.rb
@@ -15,9 +15,7 @@
 #
 module Trino
   module Client
-
-    require 'trino/client/version'
-    require 'trino/client/client'
-
+    require "trino/client/version"
+    require "trino/client/client"
   end
 end
diff --git a/modelgen/modelgen.rb b/modelgen/modelgen.rb
index ece2f669..ece6ff66 100644
--- a/modelgen/modelgen.rb
+++ b/modelgen/modelgen.rb
@@ -1,4 +1,3 @@
-
 if ARGV.length != 4
   puts "usage: <model-version> <trino-source-dir> <template.erb> <output.rb>"
   exit 1
@@ -70,7 +69,7 @@
 StatementStats StageStats ClientStageStats
 ClientStageStats StageStats ClientStageStats
 QueryResults Column ClientColumn
-].each_slice(3).map { |x, y, z| [[x,y], z] }.flatten(1)]
+].each_slice(3).map { |x, y, z| [[x, y], z] }.flatten(1)]
 
 path_mapping = Hash[*%w[
 ClientColumn client/trino-client/src/main/java/io/trino/client/Column.java
@@ -82,7 +81,7 @@
 TableWriterInfo core/trino-main/src/main/java/io/trino/operator/TableWriterOperator.java
 TableInfo core/trino-main/src/main/java/io/trino/execution/TableInfo.java
 DynamicFiltersStats core/trino-main/src/main/java/io/trino/server/DynamicFilterService.java
-].map.with_index { |v,i| i % 2 == 0 ? v : (source_path + "/" + v) }]
+].map.with_index { |v, i| i % 2 == 0 ? v : (source_path + "/" + v) }]
 
 # model => [ [key,nullable,type], ... ]
 extra_fields = {
@@ -107,7 +106,7 @@
   primitive_types: assume_primitive,
   skip_types: skipped_models,
   simple_classes: predefined_simple_classes,
-  enum_types: enum_types,
+  enum_types: enum_types
 )
 formatter.format(models)
 
@@ -116,4 +115,3 @@
 
 data = erb.result
 File.write(output_path, data)
-
diff --git a/modelgen/trino_models.rb b/modelgen/trino_models.rb
index df07f0c8..5ea602d9 100644
--- a/modelgen/trino_models.rb
+++ b/modelgen/trino_models.rb
@@ -1,4 +1,3 @@
-
 module TrinoModels
   require 'find'
   require 'stringio'
@@ -15,7 +14,7 @@ class Field < Struct.new(:key, :nullable, :array, :map, :type, :base_type, :map_
     alias_method :map?, :map
 
     def name
-      @name ||= key.gsub(/[A-Z]/) {|f| "_#{f.downcase}" }
+      @name ||= key.gsub(/[A-Z]/) { |f| "_#{f.downcase}" }
     end
   end
 
@@ -23,7 +22,7 @@ class ModelAnalysisError < StandardError
   end
 
   class ModelAnalyzer
-    def initialize(source_path, options={})
+    def initialize(source_path, options = {})
       @source_path = source_path
       @ignore_types = PRIMITIVE_TYPES + ARRAY_PRIMITIVE_TYPES + (options[:skip_models] || [])
       @path_mapping = options[:path_mapping] || {}
@@ -36,11 +35,11 @@ def initialize(source_path, options={})
     attr_reader :skipped_models
 
     def models
-      @models.values.sort_by {|model| model.name }
+      @models.values.sort_by { |model| model.name }
     end
 
     def analyze(root_models)
-      root_models.each {|model_name|
+      root_models.each { |model_name|
         analyze_model(model_name)
       }
     end
@@ -54,7 +53,7 @@ def analyze(root_models)
     def analyze_fields(model_name, creator_block, generic: nil)
       model_name = "#{model_name}_#{generic}" if generic
       extra = @extra_fields[model_name] || []
-      fields = creator_block.scan(PROPERTY_PATTERN).concat(extra).map do |key,nullable,type|
+      fields = creator_block.scan(PROPERTY_PATTERN).concat(extra).map do |key, nullable, type|
         map = false
         array = false
         nullable = !!nullable
@@ -84,10 +83,10 @@ def analyze_fields(model_name, creator_block, generic: nil)
         end
         base_type = @name_mapping[[model_name, base_type]] || base_type
         map_value_base_type = @name_mapping[[model_name, map_value_base_type]] || map_value_base_type
-        
+
         if generic
           base_type = generic if base_type == 'T'
-          map_value_base_type = generic if map_value_base_type == 'T'  
+          map_value_base_type = generic if map_value_base_type == 'T'
         end
         if m = GENERIC_PATTERN.match(base_type)
           base_type_alias = "#{m[1]}_#{m[2]}"
@@ -103,10 +102,10 @@ def analyze_fields(model_name, creator_block, generic: nil)
         analyze_model(field.map_value_base_type, model_name) if field.map_value_base_type
       end
 
-      return fields
+      fields
     end
 
-    def analyze_model(model_name, parent_model=  nil, generic: nil)
+    def analyze_model(model_name, parent_model = nil, generic: nil)
       return if @models[model_name] || @ignore_types.include?(model_name)
 
       if m = GENERIC_PATTERN.match(model_name)
@@ -123,7 +122,7 @@ def analyze_model(model_name, parent_model=  nil, generic: nil)
         raise ModelAnalysisError, "Can't find JsonCreator of a model class #{model_name} of #{parent_model} at #{path}"
       end
 
-      body = m[0] 
+      body = m[0]
       # check inner class first
       while true
         offset = m.end(0)
@@ -146,12 +145,12 @@ def find_class_file(model_name, parent_model)
 
       @source_files ||= Find.find(@source_path).to_a
       pattern = /\/#{model_name}.java$/
-      matched = @source_files.find_all {|path| path =~ pattern && !path.include?('/test/') && !path.include?('/verifier/')}
+      matched = @source_files.find_all { |path| path =~ pattern && !path.include?('/test/') && !path.include?('/verifier/') }
       if matched.empty?
         raise ModelAnalysisError, "Model class #{model_name} is not found"
       end
       if matched.size == 1
-        return matched.first
+        matched.first
       else
         raise ModelAnalysisError, "Model class #{model_name} of #{parent_model} found multiple match #{matched}"
       end
@@ -159,7 +158,7 @@ def find_class_file(model_name, parent_model)
   end
 
   class ModelFormatter
-    def initialize(options={})
+    def initialize(options = {})
       @indent = options[:indent] || '  '
       @base_indent_count = options[:base_indent_count] || 0
       @struct_class = options[:struct_class] || 'Struct'
@@ -182,7 +181,7 @@ def format(models)
         @model = model
 
         puts_with_indent 0, "class << #{model.name} ="
-        puts_with_indent 2, "#{@struct_class}.new(#{model.fields.map {|f| ":#{f.name}" }.join(', ')})"
+        puts_with_indent 2, "#{@struct_class}.new(#{model.fields.map { |f| ":#{f.name}" }.join(', ')})"
         format_decode
         puts_with_indent 0, "end"
         line
@@ -220,7 +219,7 @@ def format_decode
           expr = "hash[\"#{field.key}\"]"
         else
           expr = ""
-          expr << "hash[\"#{field.key}\"] && " #if field.nullable?
+          expr << "hash[\"#{field.key}\"] && " # if field.nullable?
 
           if field.map?
             key_expr = convert_expression(field.base_type, field.base_type, "k")
@@ -238,8 +237,8 @@ def format_decode
           end
         end
 
-        #comment = "# #{field.base_type}#{field.array? ? '[]' : ''} #{field.key}"
-        #puts_with_indent 3, "#{expr},  #{comment}"
+        # comment = "# #{field.base_type}#{field.array? ? '[]' : ''} #{field.key}"
+        # puts_with_indent 3, "#{expr},  #{comment}"
         puts_with_indent 3, "#{expr},"
       end
 
@@ -261,10 +260,9 @@ def convert_expression(type, base_type, key)
         key
       elsif @simple_classes.include?(base_type)
         "#{base_type}.new(#{key})"
-      else  # model class
+      else # model class
         "#{base_type}.decode(#{key})"
       end
     end
   end
 end
-
diff --git a/publish.rb b/publish.rb
index 7f04d928..2dee6069 100644
--- a/publish.rb
+++ b/publish.rb
@@ -1,5 +1,5 @@
 #!/usr/bin/env ruby
-require File.expand_path 'lib/trino/client/version', File.dirname(__FILE__)
+require File.expand_path "lib/trino/client/version", File.dirname(__FILE__)
 
 def run(cmd)
   puts cmd
@@ -11,4 +11,3 @@ def run(cmd)
 
 run("gem build trino-client-ruby/trino-client-ruby.gemspec")
 run("gem push trino-client-ruby/trino-client-ruby-#{Trino::Client::VERSION}.gem")
-
diff --git a/release.rb b/release.rb
index 0f74e4a6..31ec6ddc 100644
--- a/release.rb
+++ b/release.rb
@@ -1,8 +1,8 @@
 #!/usr/bin/env ruby
 
-require 'fileutils'
+require "fileutils"
 
-PREFIX = 'https://github.com/treasure-data/trino-client-ruby'
+PREFIX = "https://github.com/treasure-data/trino-client-ruby"
 RELEASE_NOTES_FILE = "ChangeLog.md"
 
 last_tag = `git describe --tags --abbrev=0`.chomp
@@ -21,8 +21,8 @@
 new_release_notes = []
 new_release_notes <<= "\#\# #{next_version}\n"
 new_release_notes <<= logs.split(/\n/)
-  .reject{|line| line.include?("#{last_version} release notes")}
-  .map{|x|
+  .reject { |line| line.include?("#{last_version} release notes") }
+  .map { |x|
     rev = x[0..6]
     "- #{x[8..-1]} [[#{rev}](#{PREFIX}/commit/#{rev})]\n"
   }
@@ -36,11 +36,11 @@
 release_notes <<= notes[2..-1]
 
 TMP_RELEASE_NOTES_FILE = "#{RELEASE_NOTES_FILE}.tmp"
-File.delete(TMP_RELEASE_NOTES_FILE) if File.exists?(TMP_RELEASE_NOTES_FILE)
-File.write("#{TMP_RELEASE_NOTES_FILE}", release_notes.join)
+File.delete(TMP_RELEASE_NOTES_FILE) if File.exist?(TMP_RELEASE_NOTES_FILE)
+File.write(TMP_RELEASE_NOTES_FILE.to_s, release_notes.join)
 system("cat #{TMP_RELEASE_NOTES_FILE} | vim - -c ':f #{TMP_RELEASE_NOTES_FILE}' -c ':9'")
 
-abort("The release note file is not saved. Aborted") unless File.exists?(TMP_RELEASE_NOTES_FILE)
+abort("The release note file is not saved. Aborted") unless File.exist?(TMP_RELEASE_NOTES_FILE)
 
 def run(cmd)
   puts cmd
@@ -53,4 +53,4 @@ def run(cmd)
 # run "git commit #{RELEASE_NOTES_FILE} -m \"Add #{next_version} release notes\""
 # run "git tag v#{next_version}"
 # run "git push"
-# run "git push --tags"
\ No newline at end of file
+# run "git push --tags"
diff --git a/spec/basic_query_spec.rb b/spec/basic_query_spec.rb
index 5319e42f..04f8c170 100644
--- a/spec/basic_query_spec.rb
+++ b/spec/basic_query_spec.rb
@@ -79,4 +79,4 @@
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/gzip_spec.rb b/spec/gzip_spec.rb
index b6e7ed10..f867bb7e 100644
--- a/spec/gzip_spec.rb
+++ b/spec/gzip_spec.rb
@@ -37,4 +37,4 @@
       $stdout = STDOUT
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/model_spec.rb b/spec/model_spec.rb
index 1cfd6073..5f6cadb6 100644
--- a/spec/model_spec.rb
+++ b/spec/model_spec.rb
@@ -32,4 +32,4 @@
     stats = Models::OperatorStats.decode(h)
     stats.blocked_reason.should == :waiting_for_memory
   end
-end
\ No newline at end of file
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 8f180362..0f3551ec 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -33,7 +33,7 @@ def run_with_retry(client, sql)
       return columns, rows
     rescue Trino::Client::TrinoQueryError => e
       if RETRYABLE_ERRORS.any? { |error| e.message =~ error }
-        sleep(2 ** i)
+        sleep(2**i)
         i += 1
         next
       end
diff --git a/spec/statement_client_spec.rb b/spec/statement_client_spec.rb
index b5a7461f..19bd223a 100644
--- a/spec/statement_client_spec.rb
+++ b/spec/statement_client_spec.rb
@@ -73,7 +73,7 @@
               "X-Trino-User" => options[:user],
               "X-Trino-Language" => options[:language],
               "X-Trino-Time-Zone" => options[:time_zone],
-    }).to_return(body: lambda{|req|if retry_p; response_json.to_json; else; retry_p=true; raise Timeout::Error.new("execution expired"); end })
+    }).to_return(body: lambda { |req| if retry_p; response_json.to_json; else; retry_p = true; raise Timeout::Error.new("execution expired"); end })
 
     sc = StatementClient.new(faraday, query, options.merge(http_open_timeout: 1))
     sc.has_next?.should be_true
@@ -104,7 +104,7 @@
               "X-Trino-Language" => options[:language],
               "X-Trino-Time-Zone" => options[:time_zone],
               "Accept" => "application/x-msgpack,application/json"
-    }).to_return(body: lambda{|req|if retry_p; MessagePack.dump(response_json); else; retry_p=true; raise Timeout::Error.new("execution expired"); end }, headers: {"Content-Type" => "application/x-msgpack"})
+    }).to_return(body: lambda { |req| if retry_p; MessagePack.dump(response_json); else; retry_p = true; raise Timeout::Error.new("execution expired"); end }, headers: {"Content-Type" => "application/x-msgpack"})
 
     options.merge!(http_open_timeout: 1, enable_x_msgpack: "application/x-msgpack")
     sc = StatementClient.new(faraday, query, options)
@@ -277,12 +277,12 @@
     end
 
     it "sets X-Trino-Session from properties" do
-      options[:properties] = {"hello" => "world", "name"=>"value"}
+      options[:properties] = {"hello" => "world", "name" => "value"}
 
       stub_request(:post, "localhost/v1/statement").
         with(body: query,
              headers: headers.merge({
-               "X-Trino-Session" => options[:properties].map {|k,v| "#{k}=#{v}"}.join(", ")
+               "X-Trino-Session" => options[:properties].map { |k, v| "#{k}=#{v}" }.join(", ")
              })).
         to_return(body: response_json.to_json)
 
@@ -340,7 +340,7 @@
             basic_auth: [options[:user], password]
       ).to_return(body: response_json.to_json)
 
-      options.merge!(ssl: { verify: true }, password: password)
+      options.merge!(ssl: {verify: true}, password: password)
       StatementClient.new(faraday, query, options)
     end
 
@@ -449,7 +449,6 @@
     end.should raise_error(NameError)
   end
 
-
   let :nested_json do
     nested_stats = {createTime: Time.now}
     # JSON max nesting default value is 100
@@ -552,7 +551,7 @@
       it "raises TrinoQueryTimeoutError if timeout during initial resuming" do
         stub_request(:get, "localhost/v1/next_uri").
           with(headers: headers).
-          to_return(body: lambda{|req| raise Timeout::Error.new("execution expired")})
+          to_return(body: lambda { |req| raise Timeout::Error.new("execution expired") })
 
         lambda do
           StatementClient.new(faraday, query, options.merge(timeout_type => 1), "/v1/next_uri")
@@ -562,7 +561,7 @@
       it "raises TrinoHttpError if timeout during initial resuming and #{timeout_type} < retry_timeout" do
         stub_request(:get, "localhost/v1/next_uri").
           with(headers: headers).
-          to_return(body: lambda{|req| raise Timeout::Error.new("execution expired")})
+          to_return(body: lambda { |req| raise Timeout::Error.new("execution expired") })
 
         lambda do
           StatementClient.new(faraday, query, options.merge(timeout_type => 2, retry_timeout: 1), "/v1/next_uri")
@@ -631,7 +630,5 @@
       sleep 1
       client.advance # set finished
     end
-
   end
 end
-
diff --git a/spec/tpch_query_spec.rb b/spec/tpch_query_spec.rb
index abad9204..ea86b2e2 100644
--- a/spec/tpch_query_spec.rb
+++ b/spec/tpch_query_spec.rb
@@ -38,4 +38,4 @@
     expect(columns.length).to be(8)
     expect(rows.length).to be(4)
   end
-end
\ No newline at end of file
+end
diff --git a/trino-client-ruby/lib/trino-client-ruby.rb b/trino-client-ruby/lib/trino-client-ruby.rb
index c4db0ed4..cb1019dc 100644
--- a/trino-client-ruby/lib/trino-client-ruby.rb
+++ b/trino-client-ruby/lib/trino-client-ruby.rb
@@ -1 +1 @@
-require 'trino-client'
+require "trino-client"
diff --git a/trino-client-ruby/trino-client-ruby.gemspec b/trino-client-ruby/trino-client-ruby.gemspec
index 6ccbebe4..78f239c6 100644
--- a/trino-client-ruby/trino-client-ruby.gemspec
+++ b/trino-client-ruby/trino-client-ruby.gemspec
@@ -1,4 +1,4 @@
-require File.expand_path '../lib/trino/client/version', File.dirname(__FILE__)
+require File.expand_path "../lib/trino/client/version", File.dirname(__FILE__)
 
 Gem::Specification.new do |gem|
   gem.name          = "trino-client-ruby"
@@ -6,12 +6,12 @@ Gem::Specification.new do |gem|
 
   gem.authors       = ["Sadayuki Furuhashi"]
   gem.email         = ["sf@treasure-data.com"]
-  gem.description   = %q{Trino client library}
-  gem.summary       = %q{Trino client library}
+  gem.description   = "Trino client library"
+  gem.summary       = "Trino client library"
   gem.homepage      = "https://github.com/treasure-data/trino-client-ruby"
   gem.license       = "Apache-2.0"
 
-  gem.files         = ['lib/trino-client-ruby.rb']
+  gem.files         = ["lib/trino-client-ruby.rb"]
   gem.require_paths = ["lib"]
 
   gem.required_ruby_version = ">= 1.9.1"
diff --git a/trino-client.gemspec b/trino-client.gemspec
index 8c0e81fd..4c0c660c 100644
--- a/trino-client.gemspec
+++ b/trino-client.gemspec
@@ -1,4 +1,4 @@
-require File.expand_path 'lib/trino/client/version', File.dirname(__FILE__)
+require File.expand_path "lib/trino/client/version", File.dirname(__FILE__)
 
 Gem::Specification.new do |gem|
   gem.name          = "trino-client"
@@ -6,13 +6,13 @@ Gem::Specification.new do |gem|
 
   gem.authors       = ["Sadayuki Furuhashi"]
   gem.email         = ["sf@treasure-data.com"]
-  gem.description   = %q{Trino client library}
-  gem.summary       = %q{Trino client library}
+  gem.description   = "Trino client library"
+  gem.summary       = "Trino client library"
   gem.homepage      = "https://github.com/treasure-data/trino-client-ruby"
   gem.license       = "Apache-2.0"
 
   gem.files         = `git ls-files`.split($\)
-  gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
+  gem.executables   = gem.files.grep(%r{^bin/}).map { |f| File.basename(f) }
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]
 
@@ -20,7 +20,7 @@ Gem::Specification.new do |gem|
 
   gem.add_dependency "faraday", ["~> 1.0"]
   gem.add_dependency "faraday_middleware", ["~> 1.0"]
-    gem.add_dependency "msgpack", [">= 0.7.0"]
+  gem.add_dependency "msgpack", [">= 0.7.0"]
 
   gem.add_development_dependency "rake", [">= 0.9.2", "< 11.0"]
   gem.add_development_dependency "rspec", ["~> 2.13.0"]