/// <summary> Trys to acquire the WriteLock on this directory.
/// this method is only valid if this IndexReader is directory owner.
///
/// </summary>
/// <throws> IOException If WriteLock cannot be acquired. </throws>
private void AquireWriteLock()
{
if (stale)
{
throw new System.IO.IOException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations");
}
if (this.writeLock == null)
{
Lock writeLock = directory.MakeLock(IndexWriter.WRITE_LOCK_NAME);
if (!writeLock.Obtain(IndexWriter.WRITE_LOCK_TIMEOUT))
// obtain write lock
{
throw new System.IO.IOException("Index locked for write: " + writeLock);
}
this.writeLock = writeLock;
// we have to check whether index has changed since this reader was opened.
// if so, this reader is no longer valid for deletion
if (SegmentInfos.ReadCurrentVersion(directory) > segmentInfos.GetVersion())
{
stale = true;
this.writeLock.Release();
this.writeLock = null;
throw new System.IO.IOException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations");
}
}
}
/// <summary> Reads version number from segments files. The version number counts the
/// number of changes of the index.
///
/// </summary>
/// <param name="directory">where the index resides.
/// </param>
/// <returns> version number.
/// </returns>
/// <throws> IOException if segments file cannot be read. </throws>
public static long GetCurrentVersion(Directory directory)
{
return(SegmentInfos.ReadCurrentVersion(directory));
}