netudima commented on code in PR #4785:
URL: https://github.com/apache/cassandra/pull/4785#discussion_r3187637592
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src/java/org/apache/cassandra/cql3/statements/SelectStatement.java:
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@@ -815,11 +814,21 @@ private ReadQuery getSliceCommands(QueryOptions options,
ClientState state, Colu
if (filter == null || filter.isEmpty(table.comparator))
return ReadQuery.empty(table);
- List<DecoratedKey> decoratedKeys = new ArrayList<>(keys.size());
- for (ByteBuffer key : keys)
+ List<DecoratedKey> decoratedKeys;
+ if (keys.size() == 1) // reduce allocations in collections for keys
{
+ ByteBuffer key = keys.get(0);
QueryProcessor.validateKey(key);
-
decoratedKeys.add(table.partitioner.decorateKey(ByteBufferUtil.clone(key)));
+ decoratedKeys =
Collections.singletonList(table.partitioner.decorateKey(key));
+ }
+ else
+ {
+ decoratedKeys = new ArrayList<>(keys.size());
+ for (ByteBuffer key : keys)
+ {
+ QueryProcessor.validateKey(key);
Review Comment:
I prefer to optimize for a typical scenario, here we will make the code much
more complex to support a failure scenario.
In the failure scenario we raise exceptions and so, it is already quite slow
in any case.
So, such low level optimization (we speak about saving less than 1 percent
here) like reducing of allocations for a failure scenario does not worth it..
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