Database Management Systems For Mobile

Devices

Robert L. Foster Jr.November 18, 2008

Light Weight DBMS?

•Definition

•Purpose

•Examples

•Tradeoffs

Formal Definition

•There isn’t one...

•Major DBMS’s can run on most operating systems providing full functionality: MySQl Oracle etc...

•What about embedded systems?

•Why do we need one?

DBMS For Mobile Devices

• DBMS’s for mobile device should be dedicated to optimizing at least one of the following, preferably both:

• power optimization

• memory management

• commonality: small footprints

Power Optimization

• Mobile devices such as laptops, cell phones, PDA’s, and radios have a limited power supply.

• How can we optimize our DBMS to use as few resources as possible while providing the necessary functionality?

• What is the necessary functionality for a mobile device?

Power Optimization Continued...

•Query

•Add

•Delete

•Atomicity?

Memory Management

•How much memory is available on the device at any given time?

•How much of the devices internal memory should be dedicated to the DB?

•How frequently can disk accesses be made before latency issues arise?

Examples

•There are numerous “light weight” DBMS’s dedicated to addressing these specific issues.

•How do we choose which system is the best for a given device?

Examples•What’s good for the goose is not

necessarily what’s good for the gander...

•Mobile phones have increasingly larger amounts of memory, and faster internet connections.

•Multi-Touch technology and GPS capabilities are a drain on batteries, and memory.

Metrics• What should we consider when choosing a

light weight DBMS for a device?

• Operating System

• Acidity

• Contents (Blobs, Clobs, etc...)

• Max Sizes:

• Database

• Tables

• Row Size

• Columns Per Row

• Views (caching)

Metrics Continued...Capabilities?•Union

•Intersect

•Inner Joins

•Outer Joins

•Merge

•Language?

•Cost

Options

•SQLite

•SmallSQL

•Pyrrho DBMS

•ScimoreDB

•HSQLDB

•Embedded MySQL

HSQLDB•Hyperthreaded Structured Query

Language

•Written in Java

•Offers JDBC Driver

•100-600k

•Cross Platform

•OpenOffice & Mathematica

ScimoreDB Embedded

• Distributed Query Language (DQL)

• Text based query language

• Windows Only

• C++

• ACID

• Independent process or part of your application

• Free

• 4MB (A relatively small footprint in comparison)

SmallSQL

•Java

•JDBC Driver

•200k

•No Installation Required

•Provides no network interface or user management...so what’s it good for?

SQLite• ACID

• C

• Cross Platform

• 500K

• Uses a Single Database File

• FREE!

SQLite Continued...•Not a stand alone process

•A library?

•Linked Function Calls

•Dynamically Typed (Read Weakly)

•C, C++, Java, C#, and LISP bindings available

•SQLite3

More on SQLite

• SQLite3 - Stand alone application provides:

• create database

• define tables

• insert and change rows

• run queries

• manage database

• Single application (Resides on the host machine)

SQLite Code Samples• Because of weak typing and the use of a single database file several

layers may be necessary.

• SQLiteDatabaseCalls

#include "sqlite3.h"

/*Minimal SQLite3 Interface this provides the only access to SQLite3 library functions*/

sqlite3* createDatabase(char *pFilename);int getDataFromDB(sqlite3* db, const char* sqlCommand, char** & data, int & rows, int & cols);int clearOldData(sqlite3* db, const char* sqlCommand);int insertResults(sqlite3* db, int currentTime, const char* sqlCommand);int clearEntries(sqlite3* db, const char* sqlCommand);

Code Samples Continued...

•DatabaseManager

#include "SQLDatabaseCalls.h"

//Basic Interface Provided to Client Code

void* DbHandleCreate();int DbHandleClose(void* pHandle);bool addDatatoTable(const char* sqlCommand);bool clearTable(const char* sqlCommand);bool clearTableEntry(const char* sqlCommand);char** queryEntry(const char* sqlCommand, int & rows, int & cols);void freeTable(char** table);

Code Samples Continued...

• Client Code

# include "DbManager.h"

//Uses The DatabaseManager and handles all type issues and structuresbool addPolicy(SPolicy* policy, SMode* oldMode, char* content);bool deletePolicy(const char * modeID, const char * policyID);bool queryPolicy(int argc, char** argv, int & messagelen, char*& xmlBuf);bool deleteComplaint(int argc, char** argv);bool deleteConflict(int argc, char** argv); bool deleteMode(int argc, char** argv);bool findComplaint(int argc, char** argv, int & messagelen, char*& xmlBuf);bool findConflict(int argc, char** argv, int & messagelen, char*& xmlBuf);bool findDecision(int argc, char** argv, int & messagelen, char*& xmlBuf);

SQLite IRL• 125 million copies in Mozilla Firefox.

• 20 million Mac OS X computers, each of which contains multiple copies of SQLite. (In Mac OS X v10.4 Apple introduced SQLite as a persistence layer of the Core Data API.)

• 300 million downloads of Skype. (The Skype service has 100 million registered users.)

• Nokia phones with Symbian OS version 9.4 or later. (The first one is Nokia 5800)

• Every iPhone and iPod touch.

• Google Android phones like the T-Mobile G1

Tradeoffs

•Incomplete Functionality

•Support

•ACID compliance

•Boundary Limitations (Max Sizes)

•Access Control

•Coding/Implementation overhead

References• “Comparison of relational database management systems.” Wikipedia:

The Free Encyclopedia. 15 November 2008 <http://en.wikipedia.org/wiki/Comparison_of_relational_database_management_systems>

• “SQLite.” Wikipedia: The Free Encyclopedia. 15 November 2008 <http://en.wikipedia.org/wiki/SQLite>

• “HSQLDB.” 15 November 2008 <http://hsqldb.org/>

• “SmalSQL Database - the Java Desktop Database with JDBC interface.” 15 November 2008 <http://www.smallsql.de/>

• “Scimore - High performance distributed, client/server and fully feature embeded SQL database.” 15 November 2008 <http://www.scimore.com/>

• “SQLite Documentation.” 15 November 2008 <http://www.sqlite.org/docs.html>