database 1.1.19

database

A lightweight native MySQL/MariaDB & PostgreSQL driver written in D

The goal is a native driver that re-uses the same buffers and the stack as much as possible, avoiding unnecessary allocations and work for the garbage collector

example

import std.stdio;

import mysql;


void usedb() {

    auto conn = new Connection("host=127.0.0.1;user=root;pwd=pwd;db=test");
    // auto conn = new Connection("127.0.0.1", "root", "pwd", "test", 3306);

    // change database
    conn.use("mewmew");

    // simple insert statement
    execute(conn, "insert into users (name, email) values (?, ?)", "frank", "thetank@cowabanga.com");
    auto id = conn.lastInsertId;

    struct User {
        string name;
        string email;
    }

    // simple select statement
    User[] users;
    execute(conn, "select name, email from users where id > ?", 13, (MySQLRow row) {
        users ~= row.toStruct!User;
    });


    // simple select statement
    string[string] rows;
    execute(conn, "select name, email from users where id > ?", 13, (MySQLRow row) {
        rows ~= row.toAA();
    });

    foreach(row; rows) {
        writeln(row["name"], row["email"]);
    }


    // batch inserter - inserts in packets of 128k bytes
    auto insert = inserter(conn, "users_copy", "name", "email");
    foreach(user; users)
        insert.row(user.name, user.email);
    insert.flush;


    // re-usable prepared statements
    auto upd = conn.prepare("update users set sequence = ?, login_at = ?, secret = ? where id = ?");
    ubyte[] bytes = [0x4D, 0x49, 0x4C, 0x4B];
    foreach(i; 0..100)
        execute(conn, upd, i, Clock.currTime, MySQLBinary(bytes), i);


    // passing variable or large number of arguments
    string[] names;
    string[] emails;
    int[] ids = [1, 1, 3, 5, 8, 13];
    execute(conn, "select name from users where id in " ~ ids.placeholders, ids, (MySQLRow row) {
        writeln(row.name.peek!(char[])); // peek() avoids allocation - cannot use result outside delegate
        names ~= row.name.get!string;    // get() duplicates - safe to use result outside delegate
        emails ~= row.email.get!string;
    });


    // another query example
    execute(conn, "select id, name, email from users where id > ?", 13, (size_t index /*optional*/, MySQLHeader header /*optional*/, MySQLRow row) {
        writeln(header[0].name, ": ", row.id.get!int);
        return (index < 5); // optionally return false to discard remaining results
    });


    // structured row
    execute(conn, "select name, email from users where length(name) > ?", 5, (MySQLRow row) {
        auto user = row.toStruct!User; // default is strict.yesIgnoreNull - a missing field in the row will throw
        // auto user = row.toStruct!(User, Strict.yes); // missing or null will throw
        // auto user = row.toStruct!(User, Strict.no);  // missing or null will just be ignored
        writeln(user);
    });


    // structured row with nested structs
    struct GeoRef {
        double lat;
        double lng;
    }

    struct Place {
        string name;
        GeoRef location;
    }

    execute(conn, "select name, lat as `location.lat`, lng as `location.lng` from places", (MySQLRow row) {
        auto place = row.toStruct!Place;
        writeln(place.location);
    });


    // structured row annotations
    struct PlaceFull {
        uint id;
        string name;
        @optional string thumbnail;    // ok to be null or missing
        @optional GeoRef location;     // nested fields ok to be null or missing
        @optional @as("contact_person") string contact; // optional, and sourced from field contact_person instead

        @ignore File tumbnail;    // completely ignored
    }

    execute(conn, "select id, name, thumbnail, lat as `location.lat`, lng as `location.lng`, contact_person from places", (MySQLRow row) {
        auto place = row.toStruct!PlaceFull;
        writeln(place.location);
    });


    // automated struct member uncamelcase
    @uncamel struct PlaceOwner {
        uint placeID;            // matches placeID and place_id
        uint locationId;         // matches locationId and location_id
        string ownerFirstName;   // matches ownerFirstName and owner_first_name
        string ownerLastName;    // matches ownerLastName and owner_last_name
        string feedURL;          // matches feedURL and feed_url
    }

    conn.close();
}