6a684e7c38
Switch the default serialized output of `sum` on empty / all-missing buckets back to `"value": 0` to match Elasticsearch, and gate the SQL-style `"value": null` behavior behind a new `none_if_no_match: Option<bool>` flag on `SumAggregation`. `IntermediateSum::finalize` still returns `Option<f64>` internally so the Rust API stays parallel to min/max/avg, but the ES-vs-SQL choice is made at the boundary in `IntermediateMetricResult::into_final_metric_result`: `None` is coerced to `Some(0.0)` unless `none_if_no_match` is set on the aggregation request. Adds `AggregationVariants::as_sum()` accessor for that boundary check and two end-to-end tests covering both the default ES behavior and the opt-in null behavior on an empty index.
Contributing
When adding new bucket aggregation make sure to extend the "test_aggregation_flushing" test for at least 2 levels.
Code Organization
Tantivy's aggregations have been designed to mimic the aggregations of elasticsearch.
The code is organized in submodules:
bucket
Contains all bucket aggregations, like range aggregation. These bucket aggregations group documents into buckets and can contain sub-aggregations.
metric
Contains all metric aggregations, like average aggregation. Metric aggregations do not have sub aggregations.
agg_req
agg_req contains the users aggregation request. Deserialization from json is compatible with elasticsearch aggregation requests.
agg_data
agg_data contains the users aggregation request enriched with fast field accessors etc, which are used during collection.
segment_agg_result
segment_agg_result contains the aggregation result tree, which is used for collection of a segment. agg_data is passed during collection.
intermediate_agg_result
intermediate_agg_result contains the aggregation tree for merging with other trees.
agg_result
agg_result contains the final aggregation tree.