@Override
public Sequence<Row> processSubqueryResult(
GroupByQuery subquery, GroupByQuery query, Sequence<Row> subqueryResult) {
final Set<AggregatorFactory> aggs = Sets.newHashSet();
// Nested group-bys work by first running the inner query and then materializing the results in
// an incremental
// index which the outer query is then run against. To build the incremental index, we use the
// fieldNames from
// the aggregators for the outer query to define the column names so that the index will match
// the query. If
// there are multiple types of aggregators in the outer query referencing the same fieldName, we
// will try to build
// multiple columns of the same name using different aggregator types and will fail. Here, we
// permit multiple
// aggregators of the same type referencing the same fieldName (and skip creating identical
// columns for the
// subsequent ones) and return an error if the aggregator types are different.
for (AggregatorFactory aggregatorFactory : query.getAggregatorSpecs()) {
for (final AggregatorFactory transferAgg : aggregatorFactory.getRequiredColumns()) {
if (Iterables.any(
aggs,
new Predicate<AggregatorFactory>() {
@Override
public boolean apply(AggregatorFactory agg) {
return agg.getName().equals(transferAgg.getName()) && !agg.equals(transferAgg);
}
})) {
throw new IAE(
"Inner aggregator can currently only be referenced by a single type of outer aggregator"
+ " for '%s'",
transferAgg.getName());
}
aggs.add(transferAgg);
}
}
// We need the inner incremental index to have all the columns required by the outer query
final GroupByQuery innerQuery =
new GroupByQuery.Builder(subquery)
.setAggregatorSpecs(Lists.newArrayList(aggs))
.setInterval(subquery.getIntervals())
.setPostAggregatorSpecs(Lists.<PostAggregator>newArrayList())
.build();
final GroupByQuery outerQuery =
new GroupByQuery.Builder(query)
.setLimitSpec(query.getLimitSpec().merge(subquery.getLimitSpec()))
.build();
final IncrementalIndex innerQueryResultIndex =
makeIncrementalIndex(
innerQuery.withOverriddenContext(
ImmutableMap.<String, Object>of(GroupByQueryHelper.CTX_KEY_SORT_RESULTS, true)),
subqueryResult);
// Outer query might have multiple intervals, but they are expected to be non-overlapping and
// sorted which
// is ensured by QuerySegmentSpec.
// GroupByQueryEngine can only process one interval at a time, so we need to call it once per
// interval
// and concatenate the results.
final IncrementalIndex outerQueryResultIndex =
makeIncrementalIndex(
outerQuery,
Sequences.concat(
Sequences.map(
Sequences.simple(outerQuery.getIntervals()),
new Function<Interval, Sequence<Row>>() {
@Override
public Sequence<Row> apply(Interval interval) {
return process(
outerQuery.withQuerySegmentSpec(
new MultipleIntervalSegmentSpec(ImmutableList.of(interval))),
new IncrementalIndexStorageAdapter(innerQueryResultIndex));
}
})));
innerQueryResultIndex.close();
return new ResourceClosingSequence<>(
outerQuery.applyLimit(GroupByQueryHelper.postAggregate(query, outerQueryResultIndex)),
outerQueryResultIndex);
}
