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package org.apache.cassandra.db.rows;

import org.apache.cassandra.db.*;

An iterator over the rows of a given partition that also includes deletion informations.
 An UnfilteredRowIterator contains a few partition top-level informations and is an iterator of Unfiltered, that is of either Row or RangeTombstoneMarker. An implementation of UnfilteredRowIterator must provide the following guarantees: 1. the returned Unfiltered must be in clustering order, or in reverse clustering order iff BaseRowIterator<Unfiltered>.isReverseOrder returns true. 2. the iterator should not shadow its own data. That is, no deletion (partition level deletion, row deletion, range tombstone, complex deletion) should delete anything else returned by the iterator (cell, row, ...). 3. every "start" range tombstone marker should have a corresponding "end" marker, and no other marker should be in-between this start-end pair of marker. Note that due to the previous rule this means that between a "start" and a corresponding "end" marker there can only be rows that are not deleted by the markers. Also note that when iterating in reverse order, "end" markers are returned before their "start" counterpart (i.e. "start" and "end" are always in the sense of the clustering order). Note further that the objects returned by next() are only valid until the next call to hasNext() or next(). If a consumer wants to keep a reference on the returned objects for longer than the iteration, it must make a copy of it explicitly. /**
 * An iterator over the rows of a given partition that also includes deletion informations.
 * <p>
 * An {@code UnfilteredRowIterator} contains a few partition top-level informations and is an
 * iterator of {@code Unfiltered}, that is of either {@code Row} or {@code RangeTombstoneMarker}.
 * An implementation of {@code UnfilteredRowIterator} <b>must</b> provide the following
 * guarantees:
 *   1. the returned {@code Unfiltered} must be in clustering order, or in reverse clustering
 *      order iff {@link #isReverseOrder} returns true.
 *   2. the iterator should not shadow its own data. That is, no deletion
 *      (partition level deletion, row deletion, range tombstone, complex
 *      deletion) should delete anything else returned by the iterator (cell, row, ...).
 *   3. every "start" range tombstone marker should have a corresponding "end" marker, and no other
 *      marker should be in-between this start-end pair of marker. Note that due to the
 *      previous rule this means that between a "start" and a corresponding "end" marker there
 *      can only be rows that are not deleted by the markers. Also note that when iterating
 *      in reverse order, "end" markers are returned before their "start" counterpart (i.e.
 *      "start" and "end" are always in the sense of the clustering order).
 *
 * Note further that the objects returned by next() are only valid until the
 * next call to hasNext() or next(). If a consumer wants to keep a reference on
 * the returned objects for longer than the iteration, it must make a copy of
 * it explicitly.
 */
public interface UnfilteredRowIterator extends BaseRowIterator<Unfiltered>
{
    
The partition level deletion for the partition this iterate over.
/**
     * The partition level deletion for the partition this iterate over.
     */
    public DeletionTime partitionLevelDeletion();

    
Return "statistics" about what is returned by this iterator. Those are used for
performance reasons (for delta-encoding for instance) and code should not
expect those to be exact.
/**
     * Return "statistics" about what is returned by this iterator. Those are used for
     * performance reasons (for delta-encoding for instance) and code should not
     * expect those to be exact.
     */
    public EncodingStats stats();

    
Returns whether this iterator has no data (including no deletion data).
/**
     * Returns whether this iterator has no data (including no deletion data).
     */
    public default boolean isEmpty()
    {
        return partitionLevelDeletion().isLive()
            && staticRow().isEmpty()
            && !hasNext();
    }
}