EvaluatedApplications.HoloDb 1.7.6

HoloDb

An embeddable holographic SQL database for .NET. It speaks SQL, is transactional (ACID with a write-ahead log), and stores data in a columnar engine with compiled predicates, holo-native aggregates, and hash joins — plus an optional memory-mapped larger-than-memory tier. It runs inside an EvalApp harness, so heavy work executes as compiled, resource-gated, adaptively-tuned pipelines.

Durable state is a compact snapshot of the current data plus a short write-ahead log of the writes since the last checkpoint, so recovery time is bounded by live data — not by the full history of writes. The log is folded into a fresh snapshot automatically once it grows past a threshold (HoloDbOptions.CheckpointThresholdBytes), or on demand via Checkpoint().

Durable, larger-than-memory tables

For data that outgrows RAM, create a paged table (CreatePaged / OpenPaged / PagedBulkLoad). It is stored on a page store with a buffer pool and a write-ahead log, so it is durable and its data can exceed memory — cold pages spill to disk and are demand-paged back. Whole-table COUNT/SUM/MIN/MAX/ AVG and single-column GROUP BY count/sum are answered in constant time from maintained summaries, independent of table size, so aggregates stay fast even when the data is on disk. INSERT/UPDATE/ DELETE and SELECT work through the normal SQL path once the table exists.

Paged tables enforce the primary key (unique, with O(1) WHERE pk = … point lookup), run inside explicit BEGIN/COMMIT/ROLLBACK transactions, and support the full read surface: projection, WHERE, aggregates, GROUP BY/HAVING, ORDER BY, LIMIT, DISTINCT, a single INNER JOIN to another paged table, and holographic NEAREST similarity search. Concurrent reads on a table are safe, writes are serialised, and each statement is atomic (a failed statement leaves no partial rows). Note the operational envelope: the primary-key index is kept in memory (~16 bytes per row), so for a table far larger than RAM that index is the limiting resource; the buffer pool size (CreatePaged's bufferFrames) bounds the rest.

Usage

var db = new HoloDbService(new HoloDbOptions { WalPath = "app.wal" });
db.Execute("CREATE TABLE users (id INT PRIMARY KEY, age INT, name TEXT)");
db.Execute("INSERT INTO users VALUES (1, 30, 'Ada')");

var result = await db.ExecuteAsync("SELECT name FROM users WHERE age >= 18");
foreach (var row in result.Rows) Console.WriteLine(row["name"]);

Register it with DI via services.AddHoloDb(), or attach it to an EvalApp pipeline with builder.WithHoloDb(service) and query it from any step.

License

Proprietary — this package ships the compiled library only; source is not distributed. Every capability in it is free to use; a license key is reserved for future advanced features (none are gated today). See LICENSE. Copyright (c) 2026 Dongyang Stephen Chen, trading as Evaluated Applications. All rights reserved.