ernanhughes

+++ date = “2016-05-19T23:45:48+01:00” title = “Project 8: acdb a super fast database for Android” +++

An android implementation of [CDB] (https://cr.yp.to/cdb.html) database. With some simple testing I am seeing a five to ten times increase in speed over Sqlite

acdb

======

An android implementation of CDB database

This is an implementation of [CDB] (https://cr.yp.to/cdb.html)

CDB is useful if you have a static or relatively static database.

The key concepts of CDB

1. Fast lookups
2. Low overhead
3. No size limits
4. Fast replacement

I used the source code from strangeGizmo.com

For me the testing went very well. I am seeing five to ten times improvement in speed over sqlite.

The sample application loads 500 objects into a cdb database and aan SQLList database form comparison.

Speed Comparison

This test is very simple so I would advise downloading the code and testing the performance for yourself. All these were run on and android studio vm.

Action	Sqlite	Cdb
Insert 500 objects	5490 ms	139 ms
Select 500 objects	1498 ms	116 ms
Optimised Select		52 ms

Initialization

To create a new database we select a file and use CDBMake to create the database

Create a database

CdbMake make = new CdbMake();
try {
    make.start(filepath);
    for (int i = 0; i < itemCount; ++i) {
        Product product = new Product(i, "Product " + i, i);
        make.add(ByteArrayUtil.toByteArray(product.getID()), ByteArrayUtil.toByteArray(product));
    }
    make.finish();
} catch (IOException e) {
    e.printStackTrace();
}

Inserting objects

The database is simply a key value store with bye arrays for keys and values. So no matter what you are storing in it you will be creating the keys as arrays and the values as arrays.

There is a util class included for handeling some of the conversions.

For android you may store Parcel objects here is an example

convert the parcel to and from a byte array

public static byte[] toByteArray(Parcelable parceable) {
    Parcel parcel = Parcel.obtain();
    parceable.writeToParcel(parcel, 0);
    byte[] bytes = parcel.marshall();
    parcel.recycle();
    return bytes;
}

public static Parcel unmarshall(byte[] bytes) {
    Parcel parcel = Parcel.obtain();
    parcel.unmarshall(bytes, 0, bytes.length);
    parcel.setDataPosition(0);
    return parcel;
}

public static <T> T unmarshall(byte[] bytes, Parcelable.Creator<T> creator) {
    Parcel parcel = unmarshall(bytes);
    return creator.createFromParcel(parcel);
}

public static final byte[] toByteArray(int value) {
    return new byte[]{
            (byte) (value >>> 24),
            (byte) (value >>> 16),
            (byte) (value >>> 8),
            (byte) value};
}

insert the parcel

Product product = new Product(i, "Product " + i, i);
make.add(ByteArrayUtil.toByteArray(product.getID()), ByteArrayUtil.toByteArray(product));

Unmarshal the parcel

Product product = ByteArrayUtil.unmarshall(db.find(ByteArrayUtil.toByteArray(i)), Product.CREATOR);