albertobastos commented on code in PR #15280:
URL: https://github.com/apache/pinot/pull/15280#discussion_r2016337952
##########
pinot-core/src/main/java/org/apache/pinot/core/operator/query/FilteredGroupByOperator.java:
##########
@@ -168,12 +170,16 @@ protected GroupByResultsBlock getNextBlock() {
// Check if the groups limit is reached
boolean numGroupsLimitReached = groupKeyGenerator.getNumKeys() >=
_queryContext.getNumGroupsLimit();
+ if (numGroupsLimitReached) {
+
ServerMetrics.get().addMeteredGlobalValue(ServerMeter.AGGREGATE_TIMES_NUM_GROUPS_LIMIT_REACHED,
1);
+ }
Review Comment:
After some testing this is the observed behaviour (launching a cluster with
a numGroups limit so low it is always exceeded):
- For each query against the SSE, the metric gets incremented once per each
segment the table has. That makes sense, as the engine creates a worker for
each segment and it is the worker the one that checks if the number of groups
for the current segment is above the limit.
- For each query against the MSE, the metric gets incremented the same
amount **plus one**. That's because the `MultiStageOperator` stays on top of
several Leaf operators that end up incrementing the metric themself (same as
while using the SSE) and, on the way back, the `MultiStageOperator' increments
it by one more unit.
IMHO the `MultiStageOperator` should not touch this two metrics, as they are
mantained from each worker. I removed it but left a comment explaining why, and
now the metric gets updated consistently between SSE and MSE.
Edit: the per-worker nature of this two metrics is already documented on
`ServerMeter.java`.
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