A user-defined function (UDF) is custom logic that extends a database engine. With WebAssembly, the function runs inside the database, keeping computation close to the data while providing a sandboxed execution environment. section 5.3
Wasm-based UDFs provide several practical advantages:
- Reduce client-server data transfer by processing values where they reside. section 5.3
- Run bespoke database operations without moving data into an external application. section 5.3
- Implement functions in any language that compiles to Wasm rather than only traditional UDF languages such as C or SQL. section 5.3
- Use a sandboxed runtime to extend database behavior while retaining secure and efficient execution. section 5.5
Registering encryption functions in libSQL
A libSQL workflow builds a Wasm module, converts its binary to a hexadecimal blob, and registers encryption and decryption functions in SQL. The SQL setup initializes the Wasm function table, drops existing definitions, and creates new functions with CREATE FUNCTION ... LANGUAGE wasm. section 5.3.2
cargo build --release --target wasm32-unknown-unknown
Build the database function as a release Wasm module targeting wasm32-unknown-unknown. section 5.3.2
wasm_hex_dump -i wasm_udf_example.wasm
Convert the compiled Wasm binary into hexadecimal text suitable for embedding in SQL. section 5.3.2
Listing 5.5 data/create_wasm_udfs.sql file
.init_wasm_func_table DROP FUNCTION IF EXISTS encrypt; DROP FUNCTION IF EXISTS decrypt; CREATE FUNCTION encrypt LANGUAGE wasm AS X'0061736d01...'; CREATE FUNCTION decrypt LANGUAGE wasm AS X'0061736d01...';
Initialize libSQL's Wasm function table, remove conflicting definitions, and embed the function binaries as literal blobs. section 5.3.2
