private void RunCore(IChannel ch)
{
Host.AssertValue(ch);
IDataView data = CreateAndSaveLoader();
if (!string.IsNullOrWhiteSpace(Args.Columns))
{
var args = new ChooseColumnsTransform.Arguments();
args.Column = Args.Columns
.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries).Select(s => new ChooseColumnsTransform.Column()
{
Name = s
}).ToArray();
if (Utils.Size(args.Column) > 0)
{
data = new ChooseColumnsTransform(Host, args, data);
}
}
IDataSaver saver;
if (Args.Saver != null)
{
saver = Args.Saver.CreateComponent(Host);
}
else
{
saver = new TextSaver(Host, new TextSaver.Arguments()
{
Dense = Args.Dense
});
}
var cols = new List <int>();
for (int i = 0; i < data.Schema.ColumnCount; i++)
{
if (!Args.KeepHidden && data.Schema.IsHidden(i))
{
continue;
}
var type = data.Schema.GetColumnType(i);
if (saver.IsColumnSavable(type))
{
cols.Add(i);
}
else
{
ch.Info(MessageSensitivity.Schema, "The column '{0}' will not be written as it has unsavable column type.", data.Schema.GetColumnName(i));
}
}
Host.NotSensitive().Check(cols.Count > 0, "No valid columns to save");
// Send the first N lines to console.
if (Args.Rows > 0)
{
var args = new SkipTakeFilter.TakeArguments()
{
Count = Args.Rows
};
data = SkipTakeFilter.Create(Host, args, data);
}
var textSaver = saver as TextSaver;
// If it is a text saver, utilize a special utility for this purpose.
if (textSaver != null)
{
textSaver.WriteData(data, true, cols.ToArray());
}
else
{
using (MemoryStream mem = new MemoryStream())
{
using (Stream wrapStream = new SubsetStream(mem))
saver.SaveData(wrapStream, data, cols.ToArray());
mem.Seek(0, SeekOrigin.Begin);
using (StreamReader reader = new StreamReader(mem))
{
string result = reader.ReadToEnd();
ch.Info(MessageSensitivity.UserData | MessageSensitivity.Schema, result);
}
}
}
}
/// <summary>
/// A helper method to create <see cref="SkipTakeFilter"/> transform by taking the top rows defined by the <paramref name="count"/> parameter.
/// <see cref="SkipTakeFilter"/> when created with <see cref="SkipTakeFilter.TakeArguments"/> behaves as 'TakeFilter'.
/// </summary>
/// <param name="env">Host Environment.</param>
/// <param name="input">>Input <see cref="IDataView"/>. This is the output from previous transform or loader.</param>
/// <param name="count">Number of rows to take</param>
public static IDataTransform Create(IHostEnvironment env, IDataView input, long count = SkipTakeFilter.Arguments.DefaultTake)
=> SkipTakeFilter.Create(env, new SkipTakeFilter.TakeArguments()
{
Count = count
}, input);
