// only to be used by init(), to setup the very first memtable for the cfs
public Memtable(AtomicReference<ReplayPosition> commitLogLowerBound, ColumnFamilyStore cfs) {
this.cfs = cfs;
this.commitLogLowerBound = commitLogLowerBound;
this.allocator = MEMORY_POOL.newAllocator();
this.initialComparator = cfs.metadata.comparator;
this.cfs.scheduleFlush();
this.columnsCollector = new ColumnsCollector(cfs.metadata.partitionColumns());
}
private static int estimateRowOverhead(final int count) {
// calculate row overhead
try (final OpOrder.Group group = new OpOrder().start()) {
int rowOverhead;
MemtableAllocator allocator = MEMORY_POOL.newAllocator();
ConcurrentNavigableMap<PartitionPosition, Object> partitions = new ConcurrentSkipListMap<>();
final Object val = new Object();
for (int i = 0; i < count; i++)
partitions.put(
allocator.clone(
new BufferDecoratedKey(new LongToken(i), ByteBufferUtil.EMPTY_BYTE_BUFFER), group),
val);
double avgSize = ObjectSizes.measureDeep(partitions) / (double) count;
rowOverhead =
(int) ((avgSize - Math.floor(avgSize)) < 0.05 ? Math.floor(avgSize) : Math.ceil(avgSize));
rowOverhead -= ObjectSizes.measureDeep(new LongToken(0));
rowOverhead += AtomicBTreePartition.EMPTY_SIZE;
allocator.setDiscarding();
allocator.setDiscarded();
return rowOverhead;
}
}