Module vec_ext 

sqlite-vec extension registration.

sqlite-vec provides a vec0 virtual table for approximate nearest-neighbor search. The crate (sqlite-vec) ships a static C library that must be registered with SQLite on each connection that wants vec0 tables.

Per-connection registration

We call sqlite3_vec_init(db, NULL, NULL) directly on the connection’s underlying raw *mut sqlite3 handle. This avoids sqlite3_auto_extension, which internally calls sqlite3_initialize() and conflicts with libsql’s own initialization (libsql asserts that sqlite3_config(SERIALIZED) returns SQLITE_OK, which fails if sqlite was already initialized).

Because libsql::Connection does not expose the raw handle through its public API, we obtain it by opening a lightweight raw FFI connection to the same database file. A VecConnection wraps this raw handle and provides helper methods for vec-specific operations.

Safety

sqlite3_vec_init is declared by the sqlite-vec crate as fn() (zero arguments) but the actual C function has the standard SQLite extension entry point signature (sqlite3*, char**, const sqlite3_api_routines*) -> int. We re-declare it with the correct signature and call it directly. Because the library is compiled with SQLITE_CORE, the pApi parameter is ignored (the extension calls SQLite functions directly rather than through the API struct).

Structs

VecConnection

A raw SQLite connection with sqlite-vec registered.

VecStmt

A prepared statement on a VecConnection.

Functions

open_vec_connection

Register the sqlite-vec extension on a libsql::Connection by opening a raw FFI handle to the same database and registering there.

vec_available

Check whether the sqlite-vec extension is available on a connection by trying to call vec_version(). Returns true if the extension is loaded.