Rust 拡張の例

INSTALL EXTENSION vsql_rot13;

SELECT rot13('Hello, World!');
-- 'Uryyb, Jbeyq!'

SELECT rot13(rot13('Hello, World!'));
-- 'Hello, World!' (rot13 is its own inverse)

SELECT rot13(NULL);
-- NULL

vsql_rot13/
├── Cargo.toml          # cdylib crate, depends on villagesql
├── manifest.json       # Extension metadata
├── src/
│   └── lib.rs          # Implementation + extension! registration
└── mysql-test/
    └── t/*.test        # MTR test cases

use villagesql::{InValue, VdfReturn};

/// SQL: rot13(s STRING) -> STRING
fn rot13_impl(args: &[InValue]) -> VdfReturn {
    match args.first() {
        Some(InValue::String(s)) => VdfReturn::string(rot13(s)),
        Some(InValue::Null) | None => VdfReturn::null(),
        _ => VdfReturn::error("rot13: expected a STRING argument"),
    }
}

fn rot13(s: &str) -> String {
    s.chars()
        .map(|c| match c {
            'a'..='m' | 'A'..='M' => (c as u8 + 13) as char,
            'n'..='z' | 'N'..='Z' => (c as u8 - 13) as char,
            _ => c,
        })
        .collect()
}

villagesql::extension! {
    funcs: [
        villagesql::func!(rot13_impl, "rot13",
            [villagesql::Type::String] -> villagesql::Type::String),
    ]
}

{
  "name": "vsql_rot13",
  "version": "0.1.0",
  "description": "Example VillageSQL extension: provides rot13(STRING) -> STRING",
  "author": "VillageSQL Community",
  "license": "GPL-2.0"
}

INSTALL EXTENSION vsql_rational;

CREATE TABLE measurements (id INT, ratio rational);
INSERT INTO measurements VALUES
    (1, '1/2'),
    (2, '2/4'),   -- normalizes to '1/2' on storage
    (3, '-3/6'),  -- normalizes to '-1/2'
    (4, '0/1');

SELECT id, ratio FROM measurements ORDER BY ratio;

SELECT rational_add('1/2', '1/3');     -- '5/6'
SELECT rational_mul('2/3', '3/4');     -- '1/2'
SELECT rational_to_real('22/7');       -- 3.142857...

pub fn rational_encode(s: &str) -> Result<Vec<u8>, String> {
    let (num_s, den_s) = s
        .split_once('/')
        .ok_or_else(|| format!("rational: expected 'n/d', got {s:?}"))?;
    let num: i64 = num_s.trim().parse().map_err(|e| format!("numerator: {e}"))?;
    let den: i64 = den_s.trim().parse().map_err(|e| format!("denominator: {e}"))?;
    let (n, d) = normalize(i128::from(num), i128::from(den))
        .ok_or_else(|| "rational: zero or overflowing denominator".to_string())?;
    Ok(to_bytes(n, d))
}

pub fn rational_decode(b: &[u8]) -> Result<String, String> {
    if b.len() < BYTES {
        return Err(format!("rational: expected {} bytes, got {}", BYTES, b.len()));
    }
    let (n, d) = from_bytes(b);
    Ok(format!("{n}/{d}"))
}

pub fn rational_compare(a: &[u8], b: &[u8]) -> std::cmp::Ordering {
    let (n1, d1) = from_bytes(a);
    let (n2, d2) = from_bytes(b);
    // Cross-multiply; denominators are always positive after normalization
    let lhs = i128::from(n1) * i128::from(d2);
    let rhs = i128::from(n2) * i128::from(d1);
    lhs.cmp(&rhs)
}

fn rational_add_impl(args: &[InValue]) -> VdfReturn {
    match (arg(args, 0), arg(args, 1)) {
        (Ok(Some((n1, d1))), Ok(Some((n2, d2)))) => {
            match normalize(
                i128::from(n1) * i128::from(d2) + i128::from(n2) * i128::from(d1),
                i128::from(d1) * i128::from(d2),
            ) {
                Some((n, d)) => VdfReturn::Binary(to_bytes(n, d)),
                None => VdfReturn::error("rational_add: overflow"),
            }
        }
        (Err(e), _) | (_, Err(e)) => VdfReturn::error(format!("rational_add: {e}")),
        _ => VdfReturn::null(),
    }
}

villagesql::extension! {
    funcs: [
        villagesql::func!(rational_add_impl, "rational_add",
            [villagesql::custom!("rational"), villagesql::custom!("rational")]
            -> villagesql::custom!("rational"),
            deterministic: true),
        villagesql::func!(rational_sub_impl, "rational_sub",
            [villagesql::custom!("rational"), villagesql::custom!("rational")]
            -> villagesql::custom!("rational"),
            deterministic: true),
        villagesql::func!(rational_mul_impl, "rational_mul",
            [villagesql::custom!("rational"), villagesql::custom!("rational")]
            -> villagesql::custom!("rational"),
            deterministic: true),
        villagesql::func!(rational_div_impl, "rational_div",
            [villagesql::custom!("rational"), villagesql::custom!("rational")]
            -> villagesql::custom!("rational"),
            deterministic: true),
        villagesql::func!(rational_numer_impl, "rational_numer",
            [villagesql::custom!("rational")] -> villagesql::Type::Int,
            deterministic: true),
        villagesql::func!(rational_denom_impl, "rational_denom",
            [villagesql::custom!("rational")] -> villagesql::Type::Int,
            deterministic: true),
        villagesql::func!(rational_to_real_impl, "rational_to_real",
            [villagesql::custom!("rational")] -> villagesql::Type::Real,
            deterministic: true),
    ],
    types: [
        villagesql::custom_type!(
            type_name: "rational",
            persisted_length: 16,
            max_decode_buffer_length: 42,
            encode: rational_encode,
            decode: rational_decode,
            compare: rational_compare,
            hash: rational_hash,
            default: "0/1",
        ),
    ]
}

INSTALL EXTENSION vsql_agg_sum;

CREATE TABLE t (grp INT, val INT);
INSERT INTO t VALUES (1, 10), (1, 20), (2, 100), (2, 200), (2, 300);

SELECT grp, vsql_agg_sum.agg_sum(val) AS mine, SUM(val) AS builtin FROM t GROUP BY grp ORDER BY grp;

grp	mine	builtin
1	30	30
2	600	600

INSERT INTO t VALUES (3, NULL), (3, NULL);
SELECT grp, vsql_agg_sum.agg_sum(val) AS mine, SUM(val) AS builtin FROM t GROUP BY grp ORDER BY grp;

grp	mine	builtin
1	30	30
2	600	600
3	NULL	NULL

use villagesql::{InValue, VdfReturn};

/// Accumulator for `agg_sum`: the running total for the current group.
#[derive(Default)]
struct SumState {
    total: i64,
    seen: bool,
}

/// clear: reset the total at the start of each group.
fn agg_sum_clear(state: &mut SumState) {
    state.total = 0;
    state.seen = false;
}

/// accumulate: fold one row's int into the running total.
fn agg_sum_acc(state: &mut SumState, args: &[InValue]) {
    if let Some(InValue::Int(n)) = args.first() {
        state.total += *n;
        state.seen = true;
    }
}

/// result: emit the group's total once every row has been folded in.
fn agg_sum_result(state: &SumState) -> VdfReturn {
    if state.seen {
        VdfReturn::int(state.total)
    } else {
        VdfReturn::Null
    }
}

villagesql::extension! {
    funcs: [
        villagesql::agg_func!(agg_sum_result, "agg_sum",
            [villagesql::Type::Int] -> villagesql::Type::Int,
            state: SumState, clear: agg_sum_clear, accumulate: agg_sum_acc),
    ]
}

INSTALL EXTENSION vsql_varargs;

SELECT vsql_varargs.str_join('alpha', 'beta');
SELECT vsql_varargs.str_join('a', 'b', 'c', 'd');

vsql_varargs.str_join('alpha', 'beta')
#1: alpha, beta
vsql_varargs.str_join('a', 'b', 'c', 'd')
#1: a, b, c, d

CREATE TABLE t (x VARCHAR(16), y VARCHAR(16));
INSERT INTO t VALUES ('1a', '1b'), ('2a', '2b'), ('3a', '3b');
SELECT vsql_varargs.str_join(x, y) AS joined FROM t ORDER BY x;

joined
#1: 1a, 1b
#2: 2a, 2b
#3: 3a, 3b

SELECT vsql_varargs.str_join();

ERROR 1123 (HY000): Can't initialize function 'str_join'; str_join requires at least one argument

SELECT vsql_varargs.str_join('ok', 123);

ERROR 1123 (HY000): Can't initialize function 'str_join'; str_join: every argument must be a string

SELECT vsql_varargs.arg_count();
SELECT vsql_varargs.arg_count(1, 2.5, 'mix');

vsql_varargs.arg_count()
0
vsql_varargs.arg_count(1, 2.5, 'mix')
3

use villagesql::{InValue, PrerunArgs, PrerunResult, VdfReturn};

/// Per-statement state: how many times the row handler has run this statement.
#[derive(Default)]
struct JoinState {
    calls: i64,
}

/// Validate the call and set up the statement. The server does no validation for
/// varargs, so this is the only gate.
fn str_join_prerun(args: PrerunArgs, mut out: PrerunResult<JoinState>) {
    // Reject a zero-argument call.
    if args.is_empty() {
        out.error("str_join requires at least one argument");
        return;
    }

    // Every argument must be a string.
    for i in 0..args.len() {
        if !args.type_at(i).is_some_and(|t| t.is_str()) {
            out.error("str_join: every argument must be a string");
            return;
        }
    }

    // Size the result buffer from the arg count.
    out.request_buffer_size(32 + args.len() * 64);

    // Hand the fresh counter to the server.
    out.set_state(JoinState::default());
}

/// Join a variable number of string arguments, prefixed with the per-statement
/// call count. `args` length varies with how many arguments the SQL call passed.
fn str_join(state: &mut JoinState, args: &[InValue]) -> VdfReturn {
    state.calls += 1;

    let mut joined = String::new();
    for (i, arg) in args.iter().enumerate() {
        match arg {
            InValue::String(s) => {
                if i > 0 {
                    joined.push_str(", ");
                }
                joined.push_str(s);
            }
            // A string column can carry NULL. SQL-style: NULL in -> NULL out.
            InValue::Null => return VdfReturn::Null,
            _ => return VdfReturn::error("str_join: non-string argument at runtime"),
        }
    }
    VdfReturn::string(format!("#{}: {joined}", state.calls))
}

/// Bare varargs: no prerun, no state, no validation. Returns how many arguments
/// it was called with, including zero.
fn arg_count(args: &[InValue]) -> VdfReturn {
    VdfReturn::int(i64::try_from(args.len()).unwrap_or(i64::MAX))
}

fn describe_prerun(args: PrerunArgs, mut out: PrerunResult<()>) {
    if args.is_empty() {
        out.error("describe requires at least one argument");
        return;
    }
    for i in 0..args.len() {
        let ok = args
            .type_at(i)
            .is_some_and(|t| t.is_int() || t.is_real() || t.is_str());
        if !ok {
            out.error("describe: arguments must be INT, REAL, or STRING");
            return;
        }
    }
    out.request_buffer_size(32 + args.len() * 48);
}

SELECT vsql_varargs.describe(42, 3.14e0, 'hello');

vsql_varargs.describe(42, 3.14e0, 'hello')
int:42, real:3.14, str:hello

fn point_path_prerun(args: PrerunArgs, mut out: PrerunResult<()>) {
    if args.is_empty() {
        out.error("point_path requires at least one point");
        return;
    }
    for i in 0..args.len() {
        let ok = args
            .type_at(i)
            .is_some_and(|t| t.is_custom() && t.custom_name() == Some("point2d"));
        if !ok {
            out.error("point_path: every argument must be a point2d");
            return;
        }
    }
    out.request_buffer_size(16 + args.len() * 32);
}

SELECT vsql_varargs.point_path(point2d::from_string('0,0'), point2d::from_string('1,2'), point2d::from_string('3,5'));

vsql_varargs.point_path(point2d::from_string('0,0'), point2d::from_string('1,2'), point2d::from_string('3,5'))
(0,0) -> (1,2) -> (3,5)

SELECT vsql_varargs.point_path('1,2');

ERROR 1123 (HY000): Can't initialize function 'point_path'; point_path: every argument must be a point2d

villagesql::extension! {
    funcs: [
        villagesql::varargs_func!(str_join, "str_join", [..] -> villagesql::Type::String,
            state: JoinState, prerun: str_join_prerun),
        villagesql::varargs_func!(arg_count, "arg_count", [..] -> villagesql::Type::Int),
        villagesql::varargs_func!(describe, "describe", [..] -> villagesql::Type::String,
            prerun: describe_prerun),
        villagesql::varargs_func!(point_path, "point_path", [..] -> villagesql::Type::String,
            prerun: point_path_prerun),
    ],
    types: [
        villagesql::custom_type!(
            type_name: "point2d",
            persisted_length: 8,
            max_decode_buffer_length: 32,
            encode: point_encode,
            decode: point_decode,
            compare: point_compare,
            default: "0,0",
        ),
    ]
}

# From inside the example directory -- cargo-vsql passes the suite's full path:
cargo vsql test

# Or point mysql-test-run.pl at the suite directly. A bare --suite=vsql_rot13
# fails: that form only finds suites staged inside the server's own
# mysql-test/suite/ tree, and these live in the SDK repo.
cd /path/to/villagesql/build/mysql-test
./mysql-test-run.pl --suite=/path/to/vsql-rust-sdk/examples/vsql_rot13/mysql-test
./mysql-test-run.pl --suite=/path/to/vsql-rust-sdk/examples/vsql_rational/mysql-test
./mysql-test-run.pl --suite=/path/to/vsql-rust-sdk/examples/vsql_agg_sum/mysql-test
./mysql-test-run.pl --suite=/path/to/vsql-rust-sdk/examples/vsql_varargs/mysql-test