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adding better selection of separator in header #18

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adding better selection of separator in header #18

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835fa4c
adding better selection of separator in header
ti24horas Jan 16, 2014
109d083
adding support to pass column separator to override guessing
ti24horas Jan 20, 2014
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19 changes: 9 additions & 10 deletions Sources/DataAccess/DataTableBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -115,27 +115,27 @@ public static MutableDataTable GetMutableCopy(this DataTableBuilder builder, Dat
/// <param name="builder">ignored</param>
/// <param name="filename">filename of table to load. Schema is inferred from header row.</param>
/// <returns>a in-memory table containing the topN rows from the supplied file.</returns>
public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename)
public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, char columnSeparator = default (char))
{
return ReadSampleTopN(builder, filename, 100);
return ReadSampleTopN(builder, filename, columnSeparator, 100);
}

/// <summary>
/// Return an in-memory table that contains the topN rows from the table in the filename.
/// </summary>
/// <param name="builder">ignored</param>
/// <param name="filename">filename of table to load. Schema is inferred from header row.</param>
/// <param name="topN">reads the topN rows from the table.</param>
/// <returns>a in-memory table containing the topN rows from the supplied file.</returns>
public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, int topN = 100)
public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, char columnSeparator = default(char), int topN = 100)
{
Debug.Assert(builder != null);
if (filename == null)
{
throw new ArgumentNullException("filename");
}

DataTable source = new FileStreamingDataTable(filename);
DataTable source = new FileStreamingDataTable(filename, columnSeparator);
MutableDataTable dt = Analyze.SampleTopN(source, topN);
return dt;
}
Expand All @@ -147,11 +147,11 @@ public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, str
/// <param name="builder"></param>
/// <param name="filename">filename of CSV to read</param>
/// <returns>a streaming data table for the given filename</returns>
public static DataTable ReadLazy(this DataTableBuilder builder, string filename)
public static DataTable ReadLazy(this DataTableBuilder builder, string filename, char columnSeparator = default(char))
{
Debug.Assert(builder != null);

return new FileStreamingDataTable(filename) { Name = filename };
return new FileStreamingDataTable(filename, columnSeparator) { Name = filename };
}

/// <summary>
Expand All @@ -161,14 +161,13 @@ public static DataTable ReadLazy(this DataTableBuilder builder, string filename)
/// <param name="builder"></param>
/// <param name="inputStream">input stream. Must be seekable and readable</param>
/// <returns>a streaming data table for the given filename</returns>
public static DataTable ReadLazy(this DataTableBuilder builder, Stream inputStream)
public static DataTable ReadLazy(this DataTableBuilder builder, Stream inputStream, char columnSeparator = default(char))
{
Debug.Assert(builder != null);

return new StreamingDataTable(inputStream);
return new StreamingDataTable(inputStream, columnSeparator);
}


/// <summary>
/// Create an in-memory table with 2 columns (key and value), where each row is a KeyValuePair from the dictionary.
/// </summary>
Expand Down
29 changes: 11 additions & 18 deletions Sources/DataAccess/Readers.cs
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;


namespace DataAccess
{

Expand Down Expand Up @@ -225,24 +227,15 @@ public static MutableDataTable Read(TextReader stream, char delimiter = '\0')

public static char GuessSeparateFromHeaderRow(string header)
{
if (header.Contains("\t"))
{
return '\t';
}

if (header.Contains(","))
{
return ',';
}

if (header.Contains(";"))
{
return ';';
}

// Fallback is always comma. This implies a single column.
return ',';

var validSeparators = new[] { '\t', ',', ';' };

var firstSeparator =
(from x in validSeparators.Select(c => new { separator = c, index = header.IndexOf(c) })
where x.index >= 0
orderby x.index
select x.separator).ToList();

return firstSeparator.Any() ? firstSeparator.FirstOrDefault() : ',';
}

// Read in a Ascii file that uses the given separate characters.
Expand Down
28 changes: 18 additions & 10 deletions Sources/DataAccess/StreamingDataTable.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,8 @@ internal class StreamingDataTable : TextReaderDataTable
{
readonly Stream _input;

public StreamingDataTable(Stream input)
public StreamingDataTable(Stream input, char columnSeparator)
: base(columnSeparator)
{
// We could optimize to avoid requiring CanSeek if we failed on attemps
// to read the the rows multiple times.
Expand All @@ -30,7 +31,7 @@ protected override TextReader OpenText()
{
_input.Position = 0;


return new StreamReader(_input);
}
protected override void CloseText(TextReader reader)
Expand All @@ -43,8 +44,9 @@ protected override void CloseText(TextReader reader)
internal class FileStreamingDataTable : TextReaderDataTable
{
private readonly string _filename;

public FileStreamingDataTable(string filename)

public FileStreamingDataTable(string filename, char columnSeparator)
: base(columnSeparator)
{
_filename = filename;
}
Expand All @@ -65,9 +67,15 @@ protected override void CloseText(TextReader reader)
/// </summary>
internal abstract class TextReaderDataTable : DataTable
{
private readonly char columnSeparator;

private string[] _names;


protected TextReaderDataTable(char columnSeparator)
{
this.columnSeparator = columnSeparator;
}

public override IEnumerable<string> ColumnNames
{
get
Expand All @@ -77,10 +85,10 @@ public override IEnumerable<string> ColumnNames
TextReader sr = null;
try
{
sr = this.OpenText();
sr = this.OpenText();
// First get columns.
string header = sr.ReadLine();
char ch = Reader.GuessSeparateFromHeaderRow(header);
char ch = this.columnSeparator == default(char) ? Reader.GuessSeparateFromHeaderRow(header) : this.columnSeparator;
_names = Reader.split(header, ch);
}
finally
Expand All @@ -100,7 +108,7 @@ public override IEnumerable<string> ColumnNames
// called on reader from OpenText
// Don't call dipose because that can close streams.
protected abstract void CloseText(TextReader reader);

public override IEnumerable<Row> Rows
{
get
Expand All @@ -113,7 +121,7 @@ public override IEnumerable<Row> Rows
sr = this.OpenText();

string header = sr.ReadLine(); // skip past header
char chSeparator = Reader.GuessSeparateFromHeaderRow(header);
char chSeparator = this.columnSeparator == default(char) ? Reader.GuessSeparateFromHeaderRow(header) : this.columnSeparator;

int illegal = 0;
string line;
Expand All @@ -124,7 +132,7 @@ public override IEnumerable<Row> Rows
{

string[] parts = Reader.split(line, chSeparator);

// $$$ Major hack for dealing with newlines in quotes strings.
// The better fix here would be to switch to a streaming interface.
if (parts.Length != columnCount)
Expand Down