Feature support¶

The emulator is a preview (v0.x) project. Support is tracked across several complementary artifacts rather than a single markdown matrix.

Quick reference¶

Area	Where to look	What it covers
REST API endpoints	REST API	Per-method status: `done`, `wired`, `todo`
SQL execution routes	Engine policy	DuckDB fast path, semantic executor, stubs
Capability roadmap	ROADMAP	Milestone narrative and design rationale
Executable SQL truth	Conformance	~170 YAML fixtures pinning query behavior
Client library parity	Third-party harnesses	Go, Python, Java, Node, DataFrames, dbt

REST API coverage¶

The gateway implements the BigQuery v2 REST surface end-to-end for the core resources (projects, datasets, tables, tabledata, jobs, queries, routines). Many ancillary surfaces (models, migration, data transfer, IAM custom methods) are wired stubs that return structurally-valid empty pages or 501 so client libraries probe successfully at startup.

See the full endpoint → handler mapping in REST API.

SQL & engine routes¶

Query execution dispatches through a route classifier. Each resolved AST shape lands on one of:

Route	Role
`duckdb_native`	Fast analytical path via DuckDB SQL
`duckdb_udf` / `duckdb_rewrite`	BigQuery functions polyfilled in DuckDB
`semantic_executor`	Exact BigQuery evaluation (NUMERIC, etc.)
`control_op`	DDL / DML / catalog operations
`local_stub`	Returns a documented stub response
`unsupported`	Surfaces `UNIMPLEMENTED` to the client

Per-function and per-AST-node dispositions live in the engine source:

Benchmark support matrix¶

The bench harness compares query latency and correctness outcomes across three backends:

vantaboard — this emulator
goccy — goccy/bigquery-emulator Docker 0.8.1
BigQuery — committed golden baselines

Per-case outcomes (ok, error, wrong_result, timeout, skipped) are recorded in bench/results.json. Latency and phase charts are embedded in the root README. Regenerate locally with task bench:run then task bench:charts.

Conformance fixtures¶

YAML fixtures under conformance/fixtures/ are the executable source of truth for SQL semantics. Each fixture can assert an expected engine route:

expected:
  route: duckdb_native
  match: ordered
  rows:
    - {n: 1}

Run the full suite:

task conformance:run

Generate a routing matrix artifact:

task conformance:routing-matrix

What is intentionally unsupported¶

Authentication / IAM — tokens accepted, never validated
BQML / trained models — list returns empty; mutations return 501
Row-level access policies — list returns empty; IAM methods return 501
Migration workflows — list returns empty; create/start return 501
Data Transfer Service — list returns empty; create returns 501
Legacy SQL dialect — only GoogleSQL (narrow bracket-ref translation for samples)

See Engine policy for the full route catalog and specialized feature families (ML, GIS, HLL, scripting, wildcards).