Embedded Databases

1
Embedded Databases

• Ben Bixby - Seevast.com, Inc.

2
Embedded Databases -Intro

• What is an embedded database?
• Runs in the same process
• How do they work?
• Usually can talk binary format directly
• What are the advantages?
• Speed
• No longer have to communicate with external
  process (IPC/Network)
• Context switching
• Local database means app server has to switch
  back and forth
• Can move load from central RDBMs to frontend app
  servers

3
Embedded Databases -Intro

• What are the disadvantages
• Concurrency
• There are consequences of running an in-process
  DB in multiple processes
• Synchronization
• Need a mechanism to synchronize processes when
  data changes
• RDBMs have this built in
• Locking
• Locking in high performance apps not an option

4
Embedded Databases -Intro

• Why/When would you want to use one
• If your application has/needs a database server
  running locally
• Many reads, few writes
• Zero writes if possible

5
Embedded Databases -Avaliable

• Some available embedded databases
• BerkeleyDB
• CacheFastMmap
• Embedded MySQL
• File System
• GDBM_File
• SQLite

6
Embedded Databases -Using

• Using embedded databases
• Code should be abstract
• Might want to swap database type
• Some are better than others for certain purposes
• Some considerations
• Performance
• Correctness
• Concurrency

7
Embedded Databases - Abstract

• Abstract embedded database code
• Data Access Layer (DAL)
• Essentially a tied hash interface
• As long as it has these basic functions
• Init
• Get
• Set
• List
• Remove
• Truncate

8
Embedded Databases Correct

• Correctness
• Does the database do what you need how you need
• Does it have the features you need
• LRU
• SQL
• Synchronization
• Automatic resizing
• Corruption recovery
• Does it work as expected

9
Embedded Databases - Concur.

• Concurrency
• Special considerations for a multi-process
  environment
• Readers
• Writers
• Locking
• Synchronization

10
Embedded Databases - Perf.

• Performance comparison
• Is it fast enough for your application
• Benchmarking

11
Embedded Databases -Concl.

• Conclusion
• Get requirements straight
• Reduce pain
• Some additional info
• MJD - "Lightweight Database Techniques" -
  http//perlmonks.org/?node_id629253
• Michael Owens - "Programming with SQLite" -
  http//conferences.oreillynet.com/cs/os2007/view/e
  _sess/12585
• Rob Mueller - "Comparison of Different Perl
  Caching Modules" - http//cpan.robm.fastmail.fm/ca
  che_perf.html
• Thank you