Reduce heap usage in BestBucketsDeferringCollector #105444
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Pinging @elastic/es-analytical-engine (Team:Analytics) |
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Hi @iverase, I've created a changelog YAML for you. |
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BestBucketsDeferringCollector delays the creation of sub-aggregations by collecting on the heap the values of documents and buckets received in LeafBucketCollector#collect(int doc, long bucket). Those values are replayed in a later stage if necessary.
We are currently using Lucene PackedLongValues to compress those integers on heap. In #103624 we added PFOR-delta for compression of postings in Elasticsearch which is probably more space efficient that the algorithm in PackedLongValues which is essentially a FOR (without the P) so likely more wasteful.
This PR introduces PForLongValues which follows the PackedLongValues API so it can easily replace the current usage of PackedLongValues in BestBucketsDeferringCollector.