/// <summary>
/// Take <paramref name="count"/> rows from <paramref name="input"/>.
/// </summary>
/// <remarks>
/// Returns returns an <see cref="IDataView"/> with the first <paramref name="count"/> rows from <paramref name="input"/>.
/// </remarks>
/// <param name="input">The input data.</param>
/// <param name="count">Number of rows to take.</param>
/// <example>
/// <format type="text/markdown">
/// <]
/// ]]>
/// </format>
/// </example>
public IDataView TakeRows(IDataView input, long count)
{
_env.CheckValue(input, nameof(input));
_env.CheckUserArg(count > 0, nameof(count), "Must be greater than zero.");
var options = new SkipTakeFilter.TakeOptions()
{
Count = count
};
return(new SkipTakeFilter(_env, options, input));
}
public static CommonOutputs.TransformOutput TakeFilter(IHostEnvironment env, SkipTakeFilter.TakeOptions input)
{
Contracts.CheckValue(env, nameof(env));
var host = env.Register("TakeFilter");
host.CheckValue(input, nameof(input));
EntryPointUtils.CheckInputArgs(host, input);
var xf = SkipTakeFilter.Create(host, input, input.Data);
return(new CommonOutputs.TransformOutput {
Model = new TransformModelImpl(env, xf, input.Data), OutputData = xf
});
}
private void RunCore(IChannel ch)
{
Host.AssertValue(ch);
IDataView data = CreateAndSaveLoader();
if (!string.IsNullOrWhiteSpace(ImplOptions.Columns))
{
var keepColumns = ImplOptions.Columns
.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries).ToArray();
if (Utils.Size(keepColumns) > 0)
{
data = ColumnSelectingTransformer.CreateKeep(Host, data, keepColumns);
}
}
IDataSaver saver;
if (ImplOptions.Saver != null)
{
saver = ImplOptions.Saver.CreateComponent(Host);
}
else
{
saver = new TextSaver(Host, new TextSaver.Arguments()
{
Dense = ImplOptions.Dense
});
}
var cols = new List <int>();
for (int i = 0; i < data.Schema.Count; i++)
{
if (!ImplOptions.KeepHidden && data.Schema[i].IsHidden)
{
continue;
}
var type = data.Schema[i].Type;
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[i].Name);
}
}
Host.NotSensitive().Check(cols.Count > 0, "No valid columns to save");
// Send the first N lines to console.
if (ImplOptions.Rows > 0)
{
var args = new SkipTakeFilter.TakeOptions()
{
Count = ImplOptions.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);
}
}
}
}
