netudima commented on code in PR #3730:
URL: https://github.com/apache/cassandra/pull/3730#discussion_r1918953416
##########
src/java/org/apache/cassandra/db/ReadCommand.java:
##########
@@ -867,6 +868,130 @@ protected LongPredicate getPurgeEvaluator()
return Transformation.apply(iterator, new
WithoutPurgeableTombstones());
}
+
+ /**
+ * Wraps the provided iterator so that metrics on count of purgeable
tombstones are tracked and traced.
+ * It tracks only tombstones with localDeletionTime < now -
gc_grace_period.
+ * Other (non-purgeable) tombstones will be tracked by regular Cassandra
logic later.
+ */
+ private UnfilteredPartitionIterator
withPurgeableTombstonesMetricRecording(UnfilteredPartitionIterator iter,
+
ColumnFamilyStore cfs)
+ {
+ class PurgeableTombstonesMetricRecording extends
Transformation<UnfilteredRowIterator>
+ {
+ private int purgeableTombstones = 0;
+
+ @Override
+ public UnfilteredRowIterator
applyToPartition(UnfilteredRowIterator iter)
+ {
+ return Transformation.apply(iter, this);
Review Comment:
yes, I do not expect a huge impact but I want to check if it is visible. We
may read many rows if we select a big enough partition and each row has some
number of cells, so MxN cells to iterate and check. As I mentioned, I suppose
frequently per-cell stats are not really needed to pay an overhead for it,
IMHO.. A configuration option can be a compromise here, like:
droppable_tobmstones_metric_granularity: disabled|row|cell
In https://issues.apache.org/jira/browse/CASSANDRA-20165 I have spent some
time already to try to reduce the number of such non-optimal places already, so
I would not like to introduce one more by myself :-D
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