Crate quarb_firebase 

Firebase Realtime Database adapter for the Quarb query engine.

An RTDB is a JSON tree, so the mapping is quarb-json‘s — objects’ fields (and arrays’ elements) as named children, scalars carrying the value, traits and ;;;type naming the JSON kind — but the tree lives on the other end of a REST API and can be enormous (the public Hacker News database has tens of millions of nodes), so nothing is ever fetched whole.

Loading model: everything lazy, one node at a time. A node materializes on first touch with a ?shallow=true GET — a scalar arrives as its value, a container as its key set — and is cached for the adapter’s lifetime. Two consequences to respect: each newly-touched node is one HTTP request, and unanchored descent (//name) over a large database walks everything it touches — keep queries anchored the way you’d keep BigQuery queries off SELECT *.

Properties are direct fetches. ::field on a node GETs path/field.json — the cheapest possible request (one scalar, no shallow walk of siblings). This is a deliberate ergonomic divergence from quarb-json (where fields are only child hops): on a remote tree, /items/42::score should cost one tiny request, and does.

References resolve by hint. RTDB has no schema, so ~> always takes a hint naming a root-relative container: ::parent~>item reads the parent field and lands on <base>/item/<value> — the same convention as the relational adapters’ hint (the target “table”). Chains work.

Target syntax: firebase://HOST/BASE/PATH[?QUERY] — e.g. firebase://hacker-news.firebaseio.com/v0. HTTPS is assumed. Anything in the query string is appended to every request: ?auth=SECRET (legacy tokens) or ?access_token=TOKEN (OAuth2) authenticate private databases; public ones need nothing.

Declared references. The database holds no schema, so the reference schema can be supplied client-side: a refs document mapping field names to root-relative target containers — {"refs": {"parent": "item", "by": "user", "kids/*": "item"}} (the field/* form declares an array field whose elements reference the target). With refs supplied, bare ~> resolves (::parent~>), and -> crosslinks enumerate: every declared field with a value becomes a labeled, probed edge, including one edge per element for array fields. An inline hint always overrides. Reverse resolution (<~) stays empty: it would require scanning the referrer container, which is exactly what opaque containers refuse (a server-side .indexOn query is the recorded v2 path).

The adapter only ever GETs; the language stays read-only.

Structs

FirebaseAdapter

A Firebase Realtime Database (subtree), exposed as an arbor.

Enums

FirebaseError

An error connecting to or reading a database.

Functions

parse_refs

Parse a refs document: {"refs": {"parent": "item", ...}}.

Type Aliases

Refs

A declared reference schema: field name (or field/* for array elements) → root-relative target container.