yashmayya commented on code in PR #13835:
URL: https://github.com/apache/pinot/pull/13835#discussion_r1746502018
##########
pinot-segment-local/src/main/java/org/apache/pinot/segment/local/aggregator/DistinctCountCPCSketchValueAggregator.java:
##########
@@ -34,11 +35,11 @@ public class DistinctCountCPCSketchValueAggregator
implements ValueAggregator<Ob
private final int _lgK;
public DistinctCountCPCSketchValueAggregator(List<ExpressionContext>
arguments) {
Review Comment:
Sketches with different `lgK` are mergeable - while the accuracy will
differ, I was initially a bit hesitant to add this check because the
`DistinctCountCPCSketchAggregationFunction` takes in the number of nominal
entries which is `2 ^ lgK` whereas `DistinctCountCPCSketchValueAggregator`
takes in `lgK` directly. So I was wondering if it'll be confusing for users to
determine which queries with `DistinctCountCPCSketchAggregationFunction` can
use the star-tree index.
However, thinking about it some more, it doesn't really make sense to allow
configuring `lgK` on a star-tree index for
`DistinctCountCPCSketchAggregationFunction` but not add the corresponding query
matching logic. I've made this change and I'll plan to add this caveat to the
documentation.
##########
pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/AggregationFunction.java:
##########
@@ -132,6 +133,32 @@ default FinalResult mergeFinalResult(FinalResult
finalResult1, FinalResult final
throw new UnsupportedOperationException("Cannot merge final results for
function: " + getType());
}
+ /**
+ * Returns whether a star-tree index with the specified properties can be
used for this aggregation function.
+ */
+ default boolean canUseStarTree(AggregationFunctionColumnPair
functionColumnPair,
Review Comment:
That's true, my original intention was to push more of that matching logic
into `AggregationFunction` itself, but I think that might require more
unrelated changes. I can remove this for now.
##########
pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/PercentileTDigestAggregationFunction.java:
##########
@@ -241,6 +243,24 @@ public Double extractFinalResult(TDigest
intermediateResult) {
return intermediateResult.quantile(_percentile / 100.0);
}
+ @Override
+ public boolean canUseStarTree(AggregationFunctionColumnPair
functionColumnPair,
+ Map<String, Object> functionParameters) {
+ if (!super.canUseStarTree(functionColumnPair, functionParameters)) {
+ return false;
+ }
+
+ // Check if compression factor matches
+ if
(functionParameters.containsKey(Constants.PERCENTILETDIGEST_COMPRESSION_FACTOR_KEY))
{
Review Comment:
They are mergeable but the percentile accuracy will differ from what the
user requested at query time, so I thought it'd be safer to only use the
star-tree index when the compression factor value matches.
##########
pinot-core/src/main/java/org/apache/pinot/core/startree/StarTreeUtils.java:
##########
@@ -363,8 +372,14 @@ public static BaseProjectOperator<?>
createStarTreeBasedProjectOperator(IndexSeg
ExpressionContext[] groupByExpressions =
queryContext.getGroupByExpressions() != null ?
queryContext.getGroupByExpressions()
.toArray(new ExpressionContext[0]) : null;
+
+ List<Pair<AggregationFunction, AggregationFunctionColumnPair>>
aggregations =
Review Comment:
Hm, the aggregation function length should be in the order of 10s at most so
I thought it wouldn't really make a difference right? I'm fine either way
though since the loop version is also pretty minimal, so I've made the change.
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