reddb-io-wire 1.34.1

//! Conservative client classification. Unknown SQL stays on the writer.

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SqlRoute {
    Replica,
    Primary,
    Begin,
    End,
    Session,
}

pub fn sql_route(sql: &str) -> SqlRoute {
    let Some(mut tokens) = sql_tokens(sql) else {
        return SqlRoute::Primary;
    };
    if tokens.last().is_some_and(|token| token == ";") {
        tokens.pop();
    }
    let Some(first) = tokens.first().map(String::as_str) else {
        return SqlRoute::Primary;
    };
    if first == "BEGIN"
        || first == "START" && tokens.get(1).is_some_and(|token| token == "TRANSACTION")
    {
        return SqlRoute::Begin;
    }
    if matches!(first, "SET" | "USE" | "PREPARE" | "DECLARE" | "LISTEN") {
        return SqlRoute::Session;
    }
    if tokens.iter().any(|token| token == ";") {
        return SqlRoute::Session;
    }
    if matches!(first, "COMMIT" | "ROLLBACK") && tokens.iter().any(|token| token == "CHAIN") {
        return SqlRoute::Begin;
    }
    if first == "COMMIT" || first == "ROLLBACK" && !tokens.iter().any(|token| token == "TO") {
        return SqlRoute::End;
    }
    if first != "SELECT" {
        return SqlRoute::Primary;
    }
    for (index, token) in tokens.iter().enumerate() {
        if matches!(
            token.as_str(),
            "INSERT"
                | "UPDATE"
                | "DELETE"
                | "CREATE"
                | "ALTER"
                | "DROP"
                | "INTO"
                | "FOR"
                | "LOCK"
                | "CALL"
                | "EXECUTE"
                | "SET"
                | "QUEUE"
                | "COPY"
                | "["
                | "]"
        ) {
            return SqlRoute::Primary;
        }
        if tokens.get(index + 1).is_some_and(|next| next == "(")
            && token
                .as_bytes()
                .first()
                .is_some_and(|byte| byte.is_ascii_alphabetic() || *byte == b'_' || *byte == b'#')
            && !matches!(
                token.as_str(),
                "COUNT"
                    | "SUM"
                    | "MIN"
                    | "MAX"
                    | "AVG"
                    | "LOWER"
                    | "UPPER"
                    | "LENGTH"
                    | "COALESCE"
                    | "ABS"
                    | "ROUND"
                    | "CAST"
                    | "IN"
                    | "EXISTS"
                    | "SELECT"
                    | "WHERE"
                    | "AND"
                    | "OR"
                    | "NOT"
                    | "FROM"
                    | "#value"
            )
        {
            return SqlRoute::Primary;
        }
    }
    SqlRoute::Replica
}

fn sql_tokens(sql: &str) -> Option<Vec<String>> {
    if sql.len() > 1_048_576 {
        return None;
    }
    let bytes = sql.as_bytes();
    let mut index = 0;
    let mut tokens = Vec::new();
    while index < bytes.len() {
        let byte = bytes[index];
        if byte.is_ascii_whitespace() {
            index += 1;
            continue;
        }
        if bytes[index..].starts_with(b"--") {
            index += 2;
            while index < bytes.len() && bytes[index] != b'\n' {
                index += 1;
            }
            continue;
        }
        if bytes[index..].starts_with(b"/*") {
            let mut depth = 1;
            index += 2;
            while index < bytes.len() && depth > 0 {
                if bytes[index..].starts_with(b"/*") {
                    depth += 1;
                    index += 2;
                } else if bytes[index..].starts_with(b"*/") {
                    depth -= 1;
                    index += 2;
                } else {
                    index += 1;
                }
                if depth > 64 {
                    return None;
                }
            }
            if depth != 0 {
                return None;
            }
            continue;
        }
        if matches!(byte, b'\'' | b'"' | b'`') {
            index += 1;
            let mut closed = false;
            while index < bytes.len() {
                if bytes[index] == b'\\' {
                    return None;
                }
                let current = bytes[index];
                index += 1;
                if current == byte {
                    if bytes.get(index) == Some(&byte) {
                        index += 1;
                        continue;
                    }
                    closed = true;
                    break;
                }
            }
            if !closed {
                return None;
            }
            tokens.push(
                if byte == b'\'' {
                    "#value"
                } else {
                    "#identifier"
                }
                .to_string(),
            );
            continue;
        }
        if byte.is_ascii_alphabetic() || byte == b'_' {
            let start = index;
            index += 1;
            while index < bytes.len()
                && (bytes[index].is_ascii_alphanumeric() || bytes[index] == b'_')
            {
                index += 1;
            }
            tokens.push(sql[start..index].to_ascii_uppercase());
        } else if byte.is_ascii() {
            tokens.push(char::from(byte).to_string());
            index += 1;
        } else {
            return None;
        }
    }
    Some(tokens)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn shared_replica_sql_policy() {
        let cases: serde_json::Value = serde_json::from_str(include_str!(
            "../../../testdata/conformance/topology/sql-policy.json"
        ))
        .unwrap();
        for case in cases.as_array().unwrap() {
            let sql = case["sql"].as_str().unwrap();
            assert_eq!(
                sql_route(sql) == SqlRoute::Replica,
                case["replica_read"].as_bool().unwrap(),
                "{sql}"
            );
        }
    }

    #[test]
    fn mutations_locks_and_unknown_functions_stay_on_writer() {
        for sql in [
            "UPDATE users SET name = $1",
            "SELECT * FROM users FOR UPDATE",
            "SELECT nextval('counter')",
            "WITH x AS (DELETE FROM users) SELECT * FROM x",
        ] {
            assert_eq!(sql_route(sql), SqlRoute::Primary, "{sql}");
        }
        assert_eq!(
            sql_route("/* read */ SELECT COUNT(*) FROM users;"),
            SqlRoute::Replica
        );
        assert_eq!(
            sql_route("SELECT 'UPDATE; DELETE' AS text"),
            SqlRoute::Replica
        );
        assert_eq!(sql_route("/* transaction */ BEGIN"), SqlRoute::Begin);
        assert_eq!(sql_route("ROLLBACK TO SAVEPOINT nested"), SqlRoute::Primary);
        assert_eq!(sql_route("COMMIT"), SqlRoute::End);
        assert_eq!(sql_route("SELECT 1; BEGIN"), SqlRoute::Session);
    }
}