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SQL-on-FHIR Viewing Room

The Viewing Room is a browser-native playground for SQL-on-FHIR v2 ViewDefinitions — the radiology reading room where you examine what a view really produces. Load or edit FHIR resources, author or edit a ViewDefinition, and the flattened SQL output recalculates live as you type. No Run button, no server: the FHIR4DS viewdef engine runs in Pyodide, the generated SQL executes on DuckDB-WASM, and nothing leaves the browser.

info

First boot takes ~30–60 seconds (Pyodide + DuckDB-WASM download); warm boots are cached. The Viewing Room needs no server.

Walkthrough​

1. Browse what's loaded​

The data pane opens on Browse — your resources grouped by type, with the ViewDefinition's target type highlighted. Switch to the Editor tab to edit the raw NDJSON (one resource per line, or a JSON array).

2. Edit and watch it recalc​

Every edit to the ViewDefinition or the resources triggers a debounced auto-recalc (~0.8 s) — the output table, SQL, and diagnostics update without pressing anything. Rapid typing collapses to the latest state.

3. Inspect the exact SQL​

The SQL tab shows the verbatim SQL the FHIR4DS generator emitted — the exact-SQL doctrine made visible: what you see is exactly what ran on DuckDB, never rewritten or prettified.

4. Read typed diagnostics​

An invalid ViewDefinition (missing select, unknown column type, malformed JSON) surfaces a typed diagnostics list — code, severity, and the engine's message — never a blank screen. Wrong-resourceType input yields a 0-rows hint that names both the view's target and what you actually loaded.

5. Load a sample​

The gallery ships six engine-verified samples: the sql-on-fhir.org reference demographics set (the default — same patients and VD as the reference playground), patient addresses (forEach), a patient + contact address union (unionAll), US Core blood pressures (deep forEach + where on component coding), questionnaire responses (repeat), and observation values (collection: true typed columns rendered as JSON arrays).

Capabilities​

  • Auto-recalc — debounced live recalculation on every edit; manual Run removed (retry-boot is the only explicit affordance).
  • Browse + Edit — grouped resource tree (vendored from the CQL Clinic data viewer) with the VD target highlighted, plus the raw NDJSON editor.
  • Exact-SQL doctrine — the SQL tab shows the generated SQL verbatim.
  • Typed diagnostics — parse/validation/evaluation errors as coded diagnostics, not stack traces.
  • Collection columns — collection: true columns render as JSON arrays with NULL chips for empty cells.
  • Web component — the same app ships as <sqlonfhir-viewing-room> with a stable bundle filename for embedding (this page embeds it).

Running locally​

cd web/viewing-room
npm install
npm run build          # bundles the wheel + fhirpath WASM extension into dist/
npx vite preview --port 5177   # COOP/COEP headers required for DuckDB-WASM

The app requires exactly one fhir4ds_v2-*.whl in public/ (built from the working tree) plus fhirpath.duckdb_extension.wasm — the build copies them into dist/assets/. The e2e journey suite runs against the preview server: npm run e2e.