Added Custom Outputter that writes the column names

Added Custom Outputter that writes the column names and optionally their
types.

Writing the data is left to the reader.

.gitattributes

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+###############################################################################
+# Set default behavior to automatically normalize line endings.
+###############################################################################
+* text=auto
+
+###############################################################################
+# Set default behavior for command prompt diff.
+#
+# This is need for earlier builds of msysgit that does not have it on by
+# default for csharp files.
+# Note: This is only used by command line
+###############################################################################
+#*.cs     diff=csharp
+
+###############################################################################
+# Set the merge driver for project and solution files
+#
+# Merging from the command prompt will add diff markers to the files if there
+# are conflicts (Merging from VS is not affected by the settings below, in VS
+# the diff markers are never inserted). Diff markers may cause the following 
+# file extensions to fail to load in VS. An alternative would be to treat
+# these files as binary and thus will always conflict and require user
+# intervention with every merge. To do so, just uncomment the entries below
+###############################################################################
+#*.sln       merge=binary
+#*.csproj    merge=binary
+#*.vbproj    merge=binary
+#*.vcxproj   merge=binary
+#*.vcproj    merge=binary
+#*.dbproj    merge=binary
+#*.fsproj    merge=binary
+#*.lsproj    merge=binary
+#*.wixproj   merge=binary
+#*.modelproj merge=binary
+#*.sqlproj   merge=binary
+#*.wwaproj   merge=binary
+
+###############################################################################
+# behavior for image files
+#
+# image files are treated as binary by default.
+###############################################################################
+#*.jpg   binary
+#*.png   binary
+#*.gif   binary
+
+###############################################################################
+# diff behavior for common document formats
+# 
+# Convert binary document formats to text before diffing them. This feature
+# is only available from the command line. Turn it on by uncommenting the 
+# entries below.
+###############################################################################
+#*.doc   diff=astextplain
+#*.DOC   diff=astextplain
+#*.docx  diff=astextplain
+#*.DOCX  diff=astextplain
+#*.dot   diff=astextplain
+#*.DOT   diff=astextplain
+#*.pdf   diff=astextplain
+#*.PDF   diff=astextplain
+#*.rtf   diff=astextplain
+#*.RTF   diff=astextplain

Examples/HeaderOutputter/HeaderOutputter.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 2013
+VisualStudioVersion = 12.0.31101.0
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{182E2583-ECAD-465B-BB50-91101D7C24CE}") = "HeaderOutputterScript", "HeaderOutputterScript\HeaderOutputterScript.usqlproj", "{C8894D8F-1CA5-45BB-9CDA-726A86DEAC9A}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HeaderOutputter", "HeaderOutputter\HeaderOutputter.csproj", "{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{C8894D8F-1CA5-45BB-9CDA-726A86DEAC9A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C8894D8F-1CA5-45BB-9CDA-726A86DEAC9A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C8894D8F-1CA5-45BB-9CDA-726A86DEAC9A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C8894D8F-1CA5-45BB-9CDA-726A86DEAC9A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal

Examples/HeaderOutputter/HeaderOutputter/Class1.cs

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+// Copyright 2016 Microsoft Corp.
+// Author: Michael Rys (mrys)
+
+using Microsoft.Analytics.Interfaces;
+using Microsoft.Analytics.Types.Sql;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+// Sample Outputter that just outputs the rowset schema as "header". It always writes the names of the columns and provides the option to write the types in a second row.
+// It does not output the content of the file (That is left as an exercise to the reader)
+//
+// At this point, the outputter requires atomic file processing (ie, the file is not split into parallel extends). 
+// Once the Output model provides a way to identify the beginning of the file, this restriction can be removed.
+//
+// USAGE examples:
+//
+// OUTPUT @res USING new HeaderOutputter.HeaderOutputter(quoting:true, with_types:true, encoding:Encoding.Unicode); 
+// OUTPUT @res USING HeaderOutputter.Factory.Columns();
+// OUTPUT @res USING HeaderOutputter.Factory.ColumnsAndTypes();
+
+namespace HeaderOutputter
+{
+    [SqlUserDefinedOutputter(AtomicFileProcessing = true)]
+    public class HeaderOutputter : IOutputter
+    {
+        private string _row_delim;
+        private char _col_delim;
+        private bool _with_types;
+        private Encoding _encoding;
+        private bool _quoting;
+        private bool _first_row_written = false;  // Makes sure we only write one header per file
+
+        // Parameter initialization
+        //
+        // row_delim sets the characters to separate the rows. Default: \r\n.
+        // col_delim sets the character to separate the columns. Default: ','.
+        // with_types indicates whether the type row should be included. Default: false.
+        // quoting indicates whether the column content is quoted with double quotes (and double quotes will be doubled). Default: true
+        // encoding sets the encoding used to set the file's encoding. Default: UTF8.
+        //
+        public HeaderOutputter(string row_delim = "\r\n", char col_delim = ',', bool with_types = false, bool quoting = true, Encoding encoding = null)
+        {
+            this._encoding = ((encoding == null) ? Encoding.UTF8 : encoding);
+            this._row_delim = row_delim;
+            this._col_delim = col_delim;
+            this._with_types = with_types;
+            this._quoting = quoting;
+        }
+
+        // AddQuotes
+        //
+        // Quotes the provided string with double quotes and doubles the contained double quotes.
+        //
+        public static string AddQuotes(string s)
+        {
+            return "\"" + s.Replace("\"", "\"\"") + "\"";
+        }
+
+        // Output
+        //
+        // Outputs the names of the rowset columns in a column separated row and optionally adds their types in a second row.
+        //
+        public override void Output(IRow row, IUnstructuredWriter output)
+        {
+            if (_first_row_written) { return; }
+            using (StreamWriter streamWriter = new StreamWriter(output.BaseStream, this._encoding))
+            {
+                streamWriter.NewLine = this._row_delim;
+                ISchema schema = row.Schema;
+                for (int i = 0; i < schema.Count(); i++)
+                {
+                    var col = schema[i];
+                    if (i > 0)
+                    {
+                        streamWriter.Write(this._col_delim);
+                    }
+                    var val = _quoting ? AddQuotes(col.Name) : col.Name;
+                    streamWriter.Write(val);
+                }
+                streamWriter.WriteLine();
+                if (_with_types)
+                {
+                    for (int i = 0; i < schema.Count(); i++)
+                    {
+                        var col = schema[i];
+                        if (i > 0)
+                        {
+                            streamWriter.Write(this._col_delim);
+                        }
+                        var val = _quoting ? AddQuotes(col.Type.FullName) : col.Type.FullName;
+                        streamWriter.Write(val);
+                    }
+                    streamWriter.WriteLine();
+                }
+            }
+            _first_row_written = true;
+        }
+    }
+
+    // Define the factory classes
+    public static class Factory
+    {
+        public static HeaderOutputter Columns(string row_delim = "\r\n", char col_delim = ',', bool quoting = true, Encoding encoding = null)
+        {
+            return new HeaderOutputter(row_delim, col_delim, false, quoting, encoding);
+        }
+
+        public static HeaderOutputter ColumnsAndTypes(string row_delim = "\r\n", char col_delim = ',', bool quoting = true, Encoding encoding = null)
+        {
+            return new HeaderOutputter(row_delim, col_delim, true, quoting, encoding);
+        }
+    }
+}

Examples/HeaderOutputter/HeaderOutputter/HeaderOutputter.csproj

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+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectTypeGuids>{416D63FD-0477-49AA-A954-A7C5B95A9B51};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <ProjectGuid>{1B3E7106-6D16-4B96-87C5-F15E18FFC08F}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>HeaderOutputter</RootNamespace>
+    <AssemblyName>HeaderOutputter</AssemblyName>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Xml" />
+    <Reference Include="Microsoft.Analytics.Interfaces" />
+    <Reference Include="Microsoft.Analytics.Types" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Class1.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
+       Other similar extension points exist, see Microsoft.Common.targets.
+  <Target Name="BeforeBuild">
+  </Target>
+  <Target Name="AfterBuild">
+  </Target>
+  -->
+</Project>

Examples/HeaderOutputter/HeaderOutputter/Properties/AssemblyInfo.cs

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+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following 
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("HeaderOutputter")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("HeaderOutputter")]
+[assembly: AssemblyCopyright("Copyright ©  2015")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible 
+// to COM components.  If you need to access a type in this assembly from 
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("c6f8d3a1-88d8-44c3-b573-37199407f8ea")]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version 
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers 
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]

Examples/HeaderOutputter/HeaderOutputterScript/HdrOutputterSamples.usql

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+// Some samples/test cases for the HeaderOutputter
+// With code behind
+
+// Create some interesting rowsets
+@simple_rs = 
+SELECT  * FROM (VALUES(1, "string", (int?) 2, DateTime.Parse("2015-12-15"))
+                   , (2, "string2", (int?) 3, DateTime.Parse("2015-12-18"))
+               ) AS T(i, str, ni, dt);
+
+@quoted_rs =
+    SELECT *
+    FROM(
+        VALUES
+        (
+            1,
+            "string",
+            (int?) 2,
+            DateTime.Parse("2015-12-15")
+        )) AS T([i], [string], [nullable int], [^] );// BUGBUG [个]);
+
+// Still to do, user-defined types
+@complex_rs =
+    SELECT * FROM (VALUES( (new SQL.ARRAY<int>{1,2}) 
+                         , (new SQL.MAP<string, int?>{{"key", 42}})
+                         , (new SQL.MAP<string, SQL.ARRAY<string>>{{"key", new SQL.ARRAY<string>{"a","b"}}})
+                         , new SQL.ARRAY<SQL.MAP<int,int?>>{new SQL.MAP<int,int?>{{1,2},{2,3}}}
+  )
+) AS T(a_int, m_s_i, m_s_as, a_mii);
+
+OUTPUT @simple_rs
+TO "/output/simple.txt"
+USING new HeaderOutputter.HeaderOutputter(quoting:false, with_types:true);
+
+OUTPUT @quoted_rs
+TO "/output/quoted.txt"
+USING new HeaderOutputter.HeaderOutputter(quoting:true, with_types:true, encoding:Encoding.Unicode);
+
+OUTPUT @quoted_rs
+TO "/output/quoted_notypes_factory.txt"
+USING HeaderOutputter.Factory.Columns(quoting:true, encoding:Encoding.Unicode);
+
+OUTPUT @quoted_rs
+TO "/output/quoted_types_factory.txt"
+USING HeaderOutputter.Factory.ColumnsAndTypes(quoting:true, encoding:Encoding.Unicode);
+
+OUTPUT @complex_rs
+TO "/output/complex.txt"
+USING new HeaderOutputter.HeaderOutputter(quoting:true, with_types:true);
+