Jeff Jirsa created CASSANDRA-12961:
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Summary: LCS needlessly checks for L0 STCS candidates multiple
times
Key: CASSANDRA-12961
URL: https://issues.apache.org/jira/browse/CASSANDRA-12961
Project: Cassandra
Issue Type: Bug
Components: Compaction
Reporter: Jeff Jirsa
Priority: Trivial
It's very likely that the check for L0 STCS candidates (if L0 is falling
behind) can be moved outside of the loop, or at very least made so that it's
not called on each loop iteration:
{code}
for (int i = generations.length - 1; i > 0; i--)
{
List<SSTableReader> sstables = getLevel(i);
if (sstables.isEmpty())
continue; // mostly this just avoids polluting the debug log
with zero scores
// we want to calculate score excluding compacting ones
Set<SSTableReader> sstablesInLevel = Sets.newHashSet(sstables);
Set<SSTableReader> remaining = Sets.difference(sstablesInLevel,
cfs.getTracker().getCompacting());
double score = (double) SSTableReader.getTotalBytes(remaining) /
(double)maxBytesForLevel(i, maxSSTableSizeInBytes);
logger.trace("Compaction score for level {} is {}", i, score);
if (score > 1.001)
{
// before proceeding with a higher level, let's see if L0 is
far enough behind to warrant STCS
CompactionCandidate l0Compaction =
getSTCSInL0CompactionCandidate();
if (l0Compaction != null)
return l0Compaction;
......
{code}
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