feat(schema,query): DISKANN indexes, the F16 element type, and a working KNN operator

[albedosehen]

Brings the vector surface to parity with surql-rs 0.33.0, so a schema defined in TypeScript reaches the same SurrealDB 3.2 features as one defined in Rust. It also repairs three things that were already broken.

Added

IndexType.DISKANN and diskannIndex(name, field, dimension, {...}) define the on-disk ANN graph the 3.2 engine parses, with DiskAnnDistanceType for the metric. It is its own enum because the engine's DISKANN metric set neither contains nor is contained by the HNSW one, so an out-of-set metric is unrepresentable rather than merely refused. MTreeVectorType gained F16, I8, and U8, which HNSW also accepts.

The engine echoes a DISKANN index with DIST / TYPE / DEGREE / L_BUILD / ALPHA always spelled, defaults filled in even when the definition never stated them, and a float ALPHA carrying a trailing f suffix. The emitter spells the defaults, canonicalAlpha renders a whole number bare, and the parser excludes the f from its capture, so a definition compares equal to its own echo instead of re-applying on every reconcile.

mtreeIndex and diskannIndex throw on an element type the engine refuses for that kind.

Fixed

Vector search emitted SQL SurrealDB v3 refuses. The query builder rendered the bare <|k|> KNN form, which belongs to the KTree era and is a parse error on v3, so vector search in this toolkit did not work against a v3 server at all. It also accepted a distance argument and then dropped it. The operator now always carries a second argument: the exploration factor when vectorSearchIndexed set one, otherwise the metric, which defaults to COSINE. The new vectorSearchIndexed(field, vector, k, ef) renders the integer form the engine plans as a KnnScan over the field's index.

The migration diff silently dropped HNSW clauses. buildIndexSql kept its own copy of the clause order that knew only UNIQUE, full-text, and MTREE, so an HNSW index in a migration rendered as a plain DEFINE INDEX ... FIELDS ... with its dimension, metric, and EFC/M tuning gone. The diff now delegates to the schema emitter (generateIndexSql, newly exported), so the two cannot drift again.

The schema parser dropped unrecognised vector element types. extractVectorType matched a fixed set of five, so an index carrying any newer element type parsed back with no type and the next reconcile saw a difference that was not there.

Two existing tests asserted the old bare <|k|> rendering and are updated to the corrected form.

Note

This toolkit emits FIELDS where the Rust, Python, and Go ports emit COLUMNS. That is the existing convention here for every index kind and SurrealDB accepts both, so it is left alone; the rendered DISKANN statement is otherwise byte-identical across all four.

Verification

232 passed (1907 steps), up from a 226-passed baseline. deno lint and deno check mod.ts clean. The 5 remaining failures are the pre-existing live-database tests (CLI ping and the four integration suites); they fail identically on a clean checkout of main, verified by stashing.