coverage.md

Quack protocol coverage

QuackDB is intentionally protocol-first, but it does not claim full DuckDB Quack protocol coverage yet. This matrix tracks the implemented surface, unsupported gaps, and the test style expected before a feature is treated as covered.

Message coverage

Quack message	Status	Coverage
Connection request	Supported	Codec tests and connection integration
Connection response	Supported	Codec tests and connection integration
Prepare request	Supported	Query, prepare, and stream integration
Prepare response	Supported	Query, prepare, and stream integration
Fetch request	Supported	Streaming/fetch continuation tests
Fetch response	Supported	Streaming/fetch continuation tests
Append request	Supported	Native append integration and quack-ts encode fixtures
Success response	Supported	Append and disconnect paths
Error response	Supported	Query, append, and transport error tests
Disconnect	Supported	DBConnection disconnect cleanup

Vector encoding coverage

Vector encoding	Decode	Encode	Notes
Flat	Supported	Supported	Primary query and append path
Constant	Supported	Not emitted	Decode expands constants to row values
Dictionary	Supported	Not emitted	Decode validates selection indexes
Sequence	Supported	Not emitted	Decode materializes generated values
FSST	Unsupported	Unsupported	Raises explicit :unsupported_vector_type; QuackDB has an internal optional :fsst bridge, but current real-server probes with repeated long strings still return flat VARCHAR chunks over Quack, so the compressed wire payload shape is not exposed by current DuckDB releases
Unknown vector ids	Unsupported	Unsupported	Raises explicit :unknown_vector_type

Logical type coverage

DuckDB logical type family	Decode	Append encode	Notes
Booleans	Supported	Supported
Signed/unsigned integers	Supported	Supported	Includes hugeint/uhugeint
Floating point	Supported	Supported
Decimal	Supported	Supported	Width-dependent physical storage
VARCHAR/CHAR	Supported	Supported	Invalid UTF-8 raises explicit errors
BLOB	Supported	Supported	Raw bytes
UUID	Supported	Partial	Decode supported; append can encode integer storage but public UUID append ergonomics are not finalized
ENUM	Supported	Partial	Decode supported; append requires encoded enum index today
BIT	Supported	Partial	Decode to bit string; append expects DuckDB bit payload bytes
BIGNUM	Supported	Supported	Elixir integers; fixture covers zero, positive, and negative large values
DATE/TIME/TIMESTAMP/TIMESTAMPTZ	Supported	Supported	Calendar-aware append encoding
TIME_NS	Supported	Supported	QuackDB.NanosecondTime
TIMESTAMP_NS	Supported	Supported	QuackDB.NanosecondTimestamp
TIME WITH TIME ZONE	Supported	Supported	QuackDB.TimeWithTimeZone
INTERVAL	Supported	Supported	QuackDB.Interval
LIST	Supported	Supported	Nested values covered by real integration
STRUCT	Supported	Supported	String-key maps on decode
ARRAY	Supported	Supported	Fixed-size metadata is encoded/decoded
MAP	Supported	Supported	Decodes to maps; duplicate keys follow Map.put/3 semantics
SQLNULL	Partial	Partial	Covered as ordinary null values, not all standalone logical-type edge cases
UNION	Unsupported	Unsupported	Should raise explicit unsupported errors
VARIANT	Unsupported	Unsupported	Should raise explicit unsupported errors
ANY/TEMPLATE/LAMBDA/POINTER	Unsupported	Unsupported	Protocol metadata reserved/unsupported
AGGREGATE_STATE	Unsupported	Unsupported	Metadata not implemented
Extension/custom types	Unsupported	Unsupported	Metadata not implemented
GEOMETRY	Partial	Partial	Decoded as WKB-compatible bytes from DuckDB spatial geometry values; semantic geometry structs are not implemented

DBConnection and client coverage

Feature	Status	Coverage
Query execution	Supported	Unit and integration
Prepare/execute	Supported	Unit and integration
Streaming/fetch continuation	Supported	Unit and integration
Transactions	Supported	Unit and integration
Native row append	Supported	Unit and integration
Native column append	Supported	Unit and integration
Ecto raw SQL	Supported	Unit and integration
Ecto analytical reads	Partial	Broad SQL-generation and integration coverage
Ecto insert/insert_all	Covered	Plain inserts, returning, insert-from-query, common upserts, on_conflict: :nothing, and explicit native append fast path covered
Ecto mutations and DDL	Partial	Schema update/delete, joined update_all, joined delete_all, rowid-filtered ordered/limited mutations, Repo.explain, transactions, and basic migrator-backed DDL covered where DuckDB SQL allows it

Conformance fixtures

Current cross-implementation fixtures compare QuackDB's append/data chunk encoding byte-for-byte with quack-ts for scalar and nested chunks. See fixtures.md for the fixture inventory, parity checklist, malformed fixtures, and fixture backlog.

Next coverage targets

Area	Next work
Real-server type matrix	Keep adding SQL-generated edge cases for standalone NULL, nested nullability, unsigned/huge values, temporal precision, and DuckDB extension types as they become stable over Quack.
Append roundtrips	Expand native append tests for null-heavy scalar/nested values, schema mismatch errors, and batch-boundary behavior.
Malformed vectors	Continue adding targeted fixtures for nested offset bounds, malformed map entries, and unsupported compressed vectors.
Unsupported logical types	Add fixtures or synthetic metadata tests for UNION, VARIANT, extension/custom types, and aggregate state once stable payloads are available.
FSST	Re-run repeated-long-string probes as DuckDB Quack evolves and capture a real compressed FSST payload if the server stops flattening string vectors before serialization.