Differences from PostgREST

FirebirdREST borrows PostgREST's URL grammar, Prefer headers, error shape and security model, so PostgREST client libraries and habits mostly carry over. Firebird is not PostgreSQL, though.

firebirdrest-js wraps supabase-js's query builder (@supabase/postgrest-js) for FirebirdREST; its test suite is the compatibility check for the list below.

Same

• select with aliases, casts, embedding, !hint, !inner, spread (...) and aggregates.
• Filters eq, neq, gt, gte, lt, lte, like, ilike, in, is, isdistinct, not., and or/and trees.
• order (including order=embed(column) on to-one embeds), limit, offset, Range, Prefer: count=exact, count=planned and count=estimated.
• POST/PATCH/PUT/DELETE (PATCH/DELETE with order and limit), Prefer: return=…, resolution=…, missing=default, tx=rollback, on_conflict, columns.
• /rpc/<name> with GET (read-only) and POST, Prefer: params=multiple-objects and params=single-object.
• JWT role switching, an anonymous role, a pre-request hook, and claims available to SQL.
• jwt-secret as an HMAC secret (also base64 encoded), a PEM key, a JWK or a JWKS, or @file; a JWT validation cache.
• server-timing-enabled and the Server-Timing header (jwt, parse, transaction, response).
• application/vnd.pgrst.object+json, CSV, OpenAPI at /, {code, message, details, hint} errors.
• Prefer: handling=strict, max-affected and timezone; query plans with Accept: application/vnd.pgrst.plan (behind db-plan-enabled).

Different

Topic	PostgREST	FirebirdREST
Namespaces	exposed schemas, Accept-Profile	the same on Firebird 6 (db-schemas, Accept-Profile, Content-Profile); Firebird 3–5 have no schemas: one namespace. Packaged routines are /rpc/package.name
Relationships across schemas	foreign keys into other exposed schemas	the same on Firebird 6: foreign keys between exposed schemas embed both ways
Identifier case	as stored	unquoted (upper case) names shown in lower case
Claims in SQL	current_setting('request.jwt.claims')::json	RDB$GET_CONTEXT('USER_TRANSACTION', 'request.jwt.claim.<name>'), one variable per claim (Firebird has no JSON functions)
Computed fields / relationships	functions taking a table row	routines whose parameters are TYPE OF COLUMN <table>.<col>
To-one computed relationship	function returning one row	executable procedure
Extra operators	fts, cs, cd, ov, JSON ->/->>, ranges, arrays	Firebird's containing, starting, similar; no JSON, array or range types in Firebird
Aggregates	off by default	on by default (db-aggregates-enabled)
Embedding	one SQL statement with lateral joins	one batched query per embed level
Roles	SET ROLE per transaction	a connection pool per role (Firebird sets the role at connect time)
Metrics	pgrst_* metrics on the admin server	firebirdrest_* metrics with their own names, at /metrics on the admin port (list)
Tracing	OpenTelemetry through a separate setup	otel-traces-endpoint: a span per request, transaction and SQL statement, joining the caller's traceparent
JWT keys from a URL	not built in	jwt-jwks-url fetches a provider's JWKS and follows key rotation
JWT cache size	jwt-cache-max-entries	the same; entries also expire after 5 minutes and when the JWKS changes
Schema reload	NOTIFY pgrst	POST_EVENT 'fbrest_reload'
Realtime	not built in (Supabase Realtime is a separate service)	GET /events/<name> streams POST_EVENTs as Server-Sent Events (events)
Unfiltered PATCH/DELETE	allowed (unless pg-safeupdate)	refused unless db-safe-updates = false
Request context cost	always set	only when the database reads it (db-request-context)
params=single-object	the body goes to a single json parameter	the body goes to a single text parameter, as JSON text
params=multiple-objects on set-returning routines	no limit	at most 1024 objects per request, their arguments within 48 KB
count=planned	the planner's estimate of the query	the table's row count from index statistics; exact for filtered requests, views and procedures
Query plans	EXPLAIN output (text or JSON), also for writes	Firebird's explained plan per statement, as text or as a JSON tree, also for writes (rolled back)
Prefer: timezone	changes how timestamptz is displayed	WITH TIME ZONE values carry a zone in Firebird, so they are converted to the requested zone; ignored on Firebird 3

| Custom media types | handler functions per media type | any concrete Accept type returns a single value as is (details); a raw request body goes to a routine's only parameter | | application/geo+json | built in | request it from a function that returns GeoJSON text |

Open an issue if you miss something.