Feature comparison

LeanCorpus covers the core indexing and search capabilities expected from a Lucene-style engine while adding .NET-specific features such as Native AOT support, asynchronous APIs, source-generated mapping, and first-class operational tooling.

The comparison is split into ordinary Markdown tables so it remains useful in GitHub reviews and on the documentation site:

How to read the tables

Mark	Meaning
✔	A direct equivalent is available.
◐	A comparable capability is available, but the API or behaviour is not equivalent.
❌	No equivalent is currently available.

Lucene.NET refers to 4.8.0-beta00018. Java Lucene refers to 10.5.1. These baselines and the checked-out LeanCorpus source were last audited on 25 August 2026. The tables describe user-visible capability rather than class-for-class API parity.

Baseline documentation: Lucene.NET 4.8.0 and Java Lucene 10.5.1.

Headline comparison

Capability	LeanCorpus	Lucene.NET 4.8	Java Lucene	Notes
Text indexing and search	✔	✔	✔	Documents, fields, postings, term dictionaries, and common query types.
Asynchronous indexing	✔	❌	❌	`ValueTask` APIs and bounded `IAsyncEnumerable<T>` ingestion.
Streaming search	✔	❌	❌	Asynchronous and segment-by-segment result streams with resource controls.
Native AOT	✔	❌	❌	Trim-safe core and reflection-free serialisation paths.
Source-generated document mapping	✔	❌	❌	Compile-time field descriptors and schema validation.
Vector and hybrid search	✔	❌	✔	HNSW, filtering, quantisation, and reciprocal-rank fusion.
Modern query families	✔	◐	✔	Includes intervals, function scoring, rescoring, and disjunction max.
Faceting and aggregations	✔	✔	✔	Term, hierarchy, drill-sideways, range/date facets, histograms and numeric aggregations are available.
Analysis and language support	✔	✔	✔	Broad core coverage with some specialised Java filters absent.
Backup and codec migration	✔	❌	❌	Manifest-backed backup, compatibility checks, inspection, and staged migration.
OpenTelemetry and search diagnostics	✔	❌	❌	Activities, metrics, slow-query records, analytics, and typed index reports.
Desktop index browser	❌	✔	✔	Lucene provides Luke; LeanCorpus provides CLI inspection instead.

Where LeanCorpus differs

LeanCorpus is designed for current .NET deployment rather than API compatibility with Lucene.NET. Public asynchronous APIs, Native AOT, source generation, System.Diagnostics telemetry, and explicit timeout and memory controls are part of that design.

Some familiar Lucene capabilities use a different shape. For example, LeanCorpus provides a hybrid highlighter rather than Java Lucene's exact Unified Highlighter, and a GeoPointField backed by a BKD tree rather than the LatLonPoint API. These are marked comparable where the distinction matters.

The tables are maintained claims, not a generated inventory. When a user-visible capability changes, update the relevant comparison page and link to its guide where a behavioural explanation is useful.