[][src]Crate extremedb

extremedb is a wrapper for the McObject's eXtremeDB database management system.

This crate currently supports the eXtremeDB SQL APIs, as well as parts of the core functionality necessary for configuring the eXtremeDB runtime, creating and opening a database, and managing database connections. Core data manipulation APIs are planned for a future release.

For more information on the eXtremeDB database management system, refer to the documentation pages.


This crate depends on the extremedb_sys crate, which has some prerequisites, as well as a few environment variables to be set. Refer to the extremedb_sys crate reference for more information.

Optional Features

  • sql — SQL engine.
  • rsql — Remote SQL engine (SQL server and client).
  • sequences — Sequences (vertical storage).

SQL Example

The example below demonstrates creating an in-memory database and using the DDL and DML SQL statements to manipulate its schema and contents.

use extremedb::connection::Connection;
use extremedb::database::{Database, Params};
use extremedb::device::{Assignment, Device};
use extremedb::runtime::Runtime;
use extremedb::sql::engine::{Engine, LocalEngine};
use extremedb::Result;

fn main() -> Result<()> {
    // Size of the memory region to allocate for the database.
    const DB_SIZE: usize = 1024 * 1024;

    // eXtremeDB runtime must be started before any operations can be performed.
    let runtime = Runtime::start(vec![]);

    // This example creates a conventional memory device, and will not work with the
    // shared memory runtime.

    // Initialize database parameters. SQL databases require these three
    // parameters to be explicitly set.
    let mut db_params = Params::new();

    // Allocate one in-memory device for the database.
    let mut devs = vec![Device::new_mem_conv(Assignment::Database, DB_SIZE)?];

    // Open the database using the parameters and devices defined above.
    let db = Database::open(&runtime, "test_db", None, &mut devs, db_params)?;

    // Establish a connection to the database.
    let conn = Connection::new(&db)?;

    // Create a local SQL engine on top of the database connection.
    let engine = LocalEngine::new(&conn)?;

    // Use SQL DDL to create a new table.
    engine.execute_statement("CREATE TABLE TestTable(i integer, s string);", &[])?;

    // Insert two rows into the table.
    engine.execute_statement("INSERT INTO TestTable(i, s) VALUES(?, ?);", &[&1, &"Hello"])?;
    engine.execute_statement("INSERT INTO TestTable(i, s) VALUES(?, ?);", &[&2, &"World"])?;

    // Select the rows.
    let ds = engine.execute_query("SELECT i, s FROM TestTable ORDER BY i;", &[])?;

    // The returned data source is not expected to be empty in case of a
    // SELECT statement.
    let ds = ds.unwrap();

    // Create a cursor to iterate over the data source.
    let mut cur = ds.cursor()?;

    // Read the first row.
        // Advance the cursor to the first row. It is positioned
        // before-the-first row initially.
        assert_eq!(cur.advance()?, true);

        // Get reference to the record which the cursor points at.
        // Since cur.advance() above has returned true, the current record
        // must not be None.
        let rec = cur.current_record();
        let rec = rec.unwrap();

        // Get the references to the values in the columns at indexes 0 and 1.
        let i_val = rec.get_at(0)?;
        let s_val = rec.get_at(1)?;

        // SQL value references must be explicitly converted to target types.
        assert_eq!(i_val.to_i64()?, 1);
        assert_eq!(s_val.to_string()?, "Hello");

    // The second row must be available.
    assert_eq!(cur.advance()?, true);

    // No more rows are expected.
    assert_eq!(cur.advance()?, false);




Database connection management.


Core database types.


Logical database devices.


eXtremeDB dictionary wrapper types.


Core return codes (generated by bindgen from MCO_RET in mco.h).


eXtremeDB runtime management.





An Error-compatible wrapper for the eXtremeDB status codes.



An error type for the core database management functions.

Type Definitions


Type alias for the eXtremeDB status codes returned by most functions.


Type alias for std::result::Result used by the eXtremeDB APIs.