Code Engine - Powered by Wasm

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Basic: This is the bare-bones Wasm ABI. It supports only 32-bit and 64-bit integers and floating point numbers.

Canonical: This ABI type is defined by the Canonical ABI specification (a part of the Interface Types proposal). It is a superset of Basic ABI, and it allows usage of structured and complex interface types.

Compile the Wasm function in "release" mode and not in debug mode. To compile in release mode,

If your program can benefit by building data structures in advance, you may improve performance by maintaining a cache in your Wasm program. For example, you can cache reusable data between function calls.

The following example caches compiled regular expressions so it does not have to compile the regular expression argument again for every row passed to the function:

wit_bindgen_rust::export!("s2regex.wit");
use regex::Regex;
use std::cell::RefCell;
use std::collections::HashMap;

struct S2regex;

thread_local! {
    static COMPILED_RGXS: RefCell<HashMap<String, Regex>> = RefCell::new(HashMap::new());
}

impl s2regex::S2regex for S2regex {
    fn capture(input: String, pattern: String) -> String {
        COMPILED_RGXS.with(|c| {
            let mut map = c.borrow_mut();
            let re = map
                .entry(pattern)
                .or_insert_with_key(|pattern| Regex::new(pattern).unwrap());
            re.captures(&input)
                .and_then(|c| c.get(1))
                .map(|c| c.as_str())
                .unwrap_or_default()
                .to_string()
        })
    }
}

The following query has to compile the regular expression only for the first row:

SELECT * FROM tbl WHERE s2regex(tbl.col, '<reg_exp_string>') = "val";

Can I use a Wasm binary outside of the SingleStoreDB database once it is imported into the database?

No. Once a Wasm binary is imported into a SingleStoreDB database, you cannot use it for applications outside the database. However, you can make a copy of the binary and use it instead.

What happens if there is a mismatch between the WIT file and the generated code?

A mismatch may cause a Wasm trap or unexpected results. The exact behavior depends on how the Wasm program interprets the arguments.

Can I reverse engineer a Wasm binary once it is imported into the database?

No. Once a Wasm binary is imported into the database, it's not possible to see the binary data, it can only be executed. Hence, you can only reverse engineer the Wasm binary behaviorally and not by disassembling the binary.

What happens when a Wasm function crashes or runs out of memory?

If a Wasm function crashes or runs out of memory, it causes the query to fail and returns an error. If possible, the error message may include a stack into the Wasm function.