bharath-techie commented on issue #13188:
URL: https://github.com/apache/lucene/issues/13188#issuecomment-2082180161
Hi @jpountz ,
Good question, if we take `StarTreeDataCube` as an example implementation of
the above format :
We will traverse the `StarTree` and `StarTreeDocValues` (dimensionDocValues
- if needed ) during query to get the resultant docIdSet.
#### StarTreeQuery
```
@Override
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode,
float boost)
throws IOException {
return new ConstantScoreWeight(this, boost) {
@Override
public Scorer scorer(LeafReaderContext context) throws IOException {
StarTreeAggregatedValues starTreeValues = null;
DocIdSetIterator result = null;
DataCubeValues<?> dataCubVals =
context.reader().getDataCubeValues(field);
Object dataCubeValues = dataCubVals.getDataCubeValues();
if (dataCubeValues != null) {
starTreeValues = (StarTreeAggregatedValues) dataCubeValues;
StarTreeFilter filter = new StarTreeFilter(starTreeValues,
filterPredicateMap, groupByCols);
// Traverse star tree and get the resultant DocIdSetIterator of
star tree + star tree doc values
result = filter.getStarTreeResult();
}
return new ConstantScoreScorer(this, score(), scoreMode, result);
}
@Override
public boolean isCacheable(LeafReaderContext ctx) {
return false;
}
};
}
```
And coming to `collector` changes, the collector needs to traverse the
`StarTreeDocValues` to get the values based on the associated `DocIds`.
For example `collect` override for `sum` aggregation will look like below
where we traverse the associated `metricDocValues`.
#### SumCollector
```
@Override
public void collect(int doc)
throws IOException {
StarTreeAggregatedValues starAggs = null;
docsBuilder.grow(1).add(doc);
DataCubeValues<?> dataCubVals =
context.reader().getDataCubeValues(field);
Object dataCubeValues = dataCubVals.getDataCubeValues();
if(starAggs != null) {
StarTreeAggregatedValues val = (StarTreeAggregatedValues) starAggs;
NumericDocValues dv = val.metricValues.get("status_sum");
dv.advanceExact(doc);
sum += dv.longValue();
}
totalHits++;
}
```
#### Example:
```
private void queryWithFilter(IndexWriter w)
throws IOException {
final IndexReader reader = DirectoryReader.open(w);
final IndexSearcher searcher = newSearcher(reader, false);
Set<String> groupByCols = new HashSet<>();
//groupByCols.add("day");
Map<String, List<Predicate<Integer>>> predicateMap = new HashMap<>();
List<Predicate<Integer>> predicates = new ArrayList<>();
predicates.add(day -> day > 2 && day < 5);
predicates.add(day -> day == 30);
predicateMap.put("day", predicates);
predicates = new ArrayList<>();
predicates.add(status -> status == 200);
predicateMap.put("status", predicates);
final Query starTreeQuery = new StarTreeQuery(predicateMap, groupByCols);
searcher.search(starTreeQuery, getStarTreeSumCollector());
```
Code
[reference](https://github.com/bharath-techie/lucene/commit/c0de03709d29991a568a27bddcf680bf2889d868#diff-a4e79e3507c88803d95fd5c9654e35c1bb0bdd72823f1300dbd6747b93e749b5)
- This contains star tree implementation but this is old code where I've not
integrated yet with DataCubes format etc. , I've followed `Approach 2 - Extend
DocValues format` but the query/collect logic should remain similar.
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