On Sat, Oct 5, 2013 at 1:48 AM, Emmanuel Lécharny <[email protected]>wrote:
> Hi,
>
> I'm currently implementing the ValueHodler for the managed btrees, and
> I'm coming with some nice solution for the duplicate values. The idea is
> to make the ValueHolder class Iterable, so that we can get any of the
> stored values in it (even if we have none or only one).
>
> This is what it will looks like :
>
> public class ValueHolder<K, V> implements Iterable<V>
> {
> /** The deserialized value */
> V[] valueArray;
>
> /** The BTree storing multiple value, if we have moe than a
> threashold values */
> BTree<V, V> valueBtree;
>
> /** The serialized value */
> ByteBuffer raw;
>
> /** A flag set to true if the values are stored in a BTree */
> boolean isBtree = false;
>
> private class ValueArrayIterator implements Iterator<V>
> {
> /** Store the current position in the array or in the BTree */
>
> private int currentPos;
>
>
> private ValueArrayIterator()
> {
> // Start at -1 to be positionned before the first element
> currentPos = -1;
> }
>
>
> @Override
> public boolean hasNext()
> {
> if ( valueArray == null )
> {
> // Load the array from the raw data
> return false;
> }
> else
> {
> return ( valueArray != null ) && ( currentPos <
> valueArray.length );
> }
> }
>
>
> public V next()
> {
> if ( valueArray == null )
> {
> // Deserialize the array
> return null;
> }
> else
> {
> currentPos++;
>
> if ( currentPos == valueArray.length )
> {
> // We have reached the end of the array
> return null;
> }
> else
> {
> return valueArray[currentPos];
> }
> }
> }
>
>
> public void remove()
> {
> // Nothing to do, we don't allow any mutation on this class
> }
> }
>
> private class ValueBtreeIterator implements Iterator<V>
> {
> /** Store the current position in the array or in the BTree */
>
> private int currentPos;
>
>
> private ValueBtreeIterator()
> {
> // Start at -1 to be positionned before the first element
> currentPos = -1;
> }
>
>
> @Override
> public boolean hasNext()
> {
> if ( valueBtree == null )
> {
> return true;
> }
> else
> {
> return true;
> }
> }
>
>
> public V next()
> {
> return null;
> }
>
>
> public void remove()
> {
> // Nothing to do, we don't allow any mutation on this class
> }
> }
>
>
> /**
> * {@inheritDoc}
> */
> @Override
> public Iterator<V> iterator()
> {
> if ( isBtree )
> {
> return new ValueBtreeIterator();
> }
> else
> {
> return new ValueArrayIterator();
> }
> }
> }
>
> As youc an see, we store either an array of Value, or a Btree. If we
> have one single value, we use an array with one single element in it.
>
> In any case, we define two different iterators which will be used
> internally, but the caller will just have to use it as is.
>
> It seems convenient, at least for a very first version, and it can be
> used by the in-memory btree too, eliminating the need of many tests in
> the implementation (things like : if ( btree.isAllowDuplicates() ).
>
> wdyt ?
>
> I prefer a cursor
> --
> Regards,
> Cordialement,
> Emmanuel Lécharny
> www.iktek.com
>
>
--
Kiran Ayyagari
http://keydap.com
