}
// next, the key cache (only make sense for valid row key)
if ((op == Operator.EQ || op == Operator.GE) && (key instanceof DecoratedKey))
{
DecoratedKey decoratedKey = (DecoratedKey)key;
KeyCacheKey cacheKey = new KeyCacheKey(descriptor, decoratedKey.key);
RowIndexEntry cachedPosition = getCachedPosition(cacheKey, updateCacheAndStats);
if (cachedPosition != null)
{
Tracing.trace("Key cache hit for sstable {}", descriptor.generation);
return cachedPosition;
}
}
// next, see if the sampled index says it's impossible for the key to be present
long sampledPosition = getIndexScanPosition(key);
if (sampledPosition == -1)
{
if (op == Operator.EQ && updateCacheAndStats)
bloomFilterTracker.addFalsePositive();
// we matched the -1th position: if the operator might match forward, we'll start at the first
// position. We however need to return the correct index entry for that first position.
if (op.apply(1) >= 0)
{
sampledPosition = 0;
}
else
{
Tracing.trace("Index sample allows skipping sstable {}", descriptor.generation);
return null;
}
}
// scan the on-disk index, starting at the nearest sampled position.
// The check against IndexInterval is to be exit the loop in the EQ case when the key looked for is not present
// (bloom filter false positive). But note that for non-EQ cases, we might need to check the first key of the
// next index position because the searched key can be greater the last key of the index interval checked if it
// is lesser than the first key of next interval (and in that case we must return the position of the first key
// of the next interval).
int i = 0;
Iterator<FileDataInput> segments = ifile.iterator(sampledPosition, INDEX_FILE_BUFFER_BYTES);
while (segments.hasNext() && i <= indexSummary.getIndexInterval())
{
FileDataInput in = segments.next();
try
{
while (!in.isEOF() && i <= indexSummary.getIndexInterval())
{
i++;
ByteBuffer indexKey = ByteBufferUtil.readWithShortLength(in);
boolean opSatisfied; // did we find an appropriate position for the op requested
boolean exactMatch; // is the current position an exact match for the key, suitable for caching
// Compare raw keys if possible for performance, otherwise compare decorated keys.
if (op == Operator.EQ)
{
opSatisfied = exactMatch = indexKey.equals(((DecoratedKey) key).key);
}
else
{
DecoratedKey indexDecoratedKey = partitioner.decorateKey(indexKey);
int comparison = indexDecoratedKey.compareTo(key);
int v = op.apply(comparison);
opSatisfied = (v == 0);
exactMatch = (comparison == 0);
if (v < 0)
{
Tracing.trace("Partition index lookup allows skipping sstable {}", descriptor.generation);
return null;
}
}
if (opSatisfied)
{
// read data position from index entry
RowIndexEntry indexEntry = RowIndexEntry.serializer.deserialize(in, descriptor.version);
if (exactMatch && updateCacheAndStats)
{
assert key instanceof DecoratedKey; // key can be == to the index key only if it's a true row key
DecoratedKey decoratedKey = (DecoratedKey)key;
if (logger.isTraceEnabled())
{
// expensive sanity check! see CASSANDRA-4687
FileDataInput fdi = dfile.getSegment(indexEntry.position);
DecoratedKey keyInDisk = partitioner.decorateKey(ByteBufferUtil.readWithShortLength(fdi));
if (!keyInDisk.equals(key))
throw new AssertionError(String.format("%s != %s in %s", keyInDisk, key, fdi.getPath()));
fdi.close();
}
// store exact match for the key