Java SSTableReader.estimatedKeysForRanges方法代码示例

import org.apache.cassandra.io.sstable.SSTableReader; //导入方法依赖的package包/类
private long estimatePartitionsCount(Collection<SSTableReader> sstables, Range<Token> range)
{
    long count = 0;
    for (SSTableReader sstable : sstables)
        count += sstable.estimatedKeysForRanges(Collections.singleton(range));
    return count;
}
 

import org.apache.cassandra.io.sstable.SSTableReader; //导入方法依赖的package包/类
/**
 * Check if given sstable is worth dropping tombstones at gcBefore.
 * Check is skipped if tombstone_compaction_interval time does not elapse since sstable creation and returns false.
 *
 * @param sstable SSTable to check
 * @param gcBefore time to drop tombstones
 * @return true if given sstable's tombstones are expected to be removed
 */
protected boolean worthDroppingTombstones(SSTableReader sstable, int gcBefore)
{
    // since we use estimations to calculate, there is a chance that compaction will not drop tombstones actually.
    // if that happens we will end up in infinite compaction loop, so first we check enough if enough time has
    // elapsed since SSTable created.
    if (System.currentTimeMillis() < sstable.getCreationTimeFor(Component.DATA) + tombstoneCompactionInterval * 1000)
       return false;

    double droppableRatio = sstable.getEstimatedDroppableTombstoneRatio(gcBefore);
    if (droppableRatio <= tombstoneThreshold)
        return false;

    //sstable range overlap check is disabled. See CASSANDRA-6563.
    if (uncheckedTombstoneCompaction)
        return true;

    Collection<SSTableReader> overlaps = cfs.getOverlappingSSTables(Collections.singleton(sstable));
    if (overlaps.isEmpty())
    {
        // there is no overlap, tombstones are safely droppable
        return true;
    }
    else if (CompactionController.getFullyExpiredSSTables(cfs, Collections.singleton(sstable), overlaps, gcBefore).size() > 0)
    {
        return true;
    }
    else
    {
        // what percentage of columns do we expect to compact outside of overlap?
        if (sstable.getIndexSummarySize() < 2)
        {
            // we have too few samples to estimate correct percentage
            return false;
        }
        // first, calculate estimated keys that do not overlap
        long keys = sstable.estimatedKeys();
        Set<Range<Token>> ranges = new HashSet<Range<Token>>(overlaps.size());
        for (SSTableReader overlap : overlaps)
            ranges.add(new Range<Token>(overlap.first.getToken(), overlap.last.getToken(), overlap.partitioner));
        long remainingKeys = keys - sstable.estimatedKeysForRanges(ranges);
        // next, calculate what percentage of columns we have within those keys
        long columns = sstable.getEstimatedColumnCount().mean() * remainingKeys;
        double remainingColumnsRatio = ((double) columns) / (sstable.getEstimatedColumnCount().count() * sstable.getEstimatedColumnCount().mean());

        // return if we still expect to have droppable tombstones in rest of columns
        return remainingColumnsRatio * droppableRatio > tombstoneThreshold;
    }
}
 

import org.apache.cassandra.io.sstable.SSTableReader; //导入方法依赖的package包/类
/**
 * Check if given sstable is worth dropping tombstones at gcBefore.
 * Check is skipped if tombstone_compaction_interval time does not elapse since sstable creation and returns false.
 *
 * @param sstable SSTable to check
 * @param gcBefore time to drop tombstones
 * @return true if given sstable's tombstones are expected to be removed
 */
protected boolean worthDroppingTombstones(SSTableReader sstable, int gcBefore)
{
    // since we use estimations to calculate, there is a chance that compaction will not drop tombstones actually.
    // if that happens we will end up in infinite compaction loop, so first we check enough if enough time has
    // elapsed since SSTable created.
    if (System.currentTimeMillis() < sstable.getCreationTimeFor(Component.DATA) + tombstoneCompactionInterval * 1000)
       return false;

    double droppableRatio = sstable.getEstimatedDroppableTombstoneRatio(gcBefore);
    if (droppableRatio <= tombstoneThreshold)
        return false;

    Set<SSTableReader> overlaps = cfs.getOverlappingSSTables(Collections.singleton(sstable));
    if (overlaps.isEmpty())
    {
        // there is no overlap, tombstones are safely droppable
        return true;
    }
    else if (CompactionController.getFullyExpiredSSTables(cfs, Collections.singleton(sstable), overlaps, gcBefore).size() > 0)
    {
        return true;
    }
    else
    {
        // what percentage of columns do we expect to compact outside of overlap?
        if (sstable.getKeySampleSize() < 2)
        {
            // we have too few samples to estimate correct percentage
            return false;
        }
        // first, calculate estimated keys that do not overlap
        long keys = sstable.estimatedKeys();
        Set<Range<Token>> ranges = new HashSet<Range<Token>>(overlaps.size());
        for (SSTableReader overlap : overlaps)
            ranges.add(new Range<Token>(overlap.first.token, overlap.last.token, overlap.partitioner));
        long remainingKeys = keys - sstable.estimatedKeysForRanges(ranges);
        // next, calculate what percentage of columns we have within those keys
        long columns = sstable.getEstimatedColumnCount().mean() * remainingKeys;
        double remainingColumnsRatio = ((double) columns) / (sstable.getEstimatedColumnCount().count() * sstable.getEstimatedColumnCount().mean());

        // return if we still expect to have droppable tombstones in rest of columns
        return remainingColumnsRatio * droppableRatio > tombstoneThreshold;
    }
}