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’s
for For
mobile
DBMS
Mobile Devices
device should be
dedicated to
optimizing at least
one of the
following,
preferably both:
• power
optimization
• memory
management
• commonality: small
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?
•
•
•
•
•
•
ACID
SQLite
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*
int
bool
bool
bool
char**
cols);
void
DbHandleCreate();
DbHandleClose(void* pHandle);
addDatatoTable(const char* sqlCommand);
clearTable(const char* sqlCommand);
clearTableEntry(const char* sqlCommand);
queryEntry(const char* sqlCommand, int & rows, int &
freeTable(char** table);
Code Samples Continued...
•
Client Code
# include "DbManager.h"
//Uses The DatabaseManager and handles all type issues and
structures
bool 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
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“Comparison of relational database management systems.”
Wikipedia: The Free Encyclopedia. 15 November 2008
<http://en.wikipedia.org/wiki/Comparison_of_relational_database_ma
nagement_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>