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What's in a Mobile Database?
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Samuel E. Giddins
March 03, 2015
Technology
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What's in a Mobile Database?
Samuel E. Giddins
March 03, 2015
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Transcript
WHAT’S IN A MOBILE DATABASE?
SAMUEL GIDDINS REALM.IO
Show of hands: WHO’S USED A DATABASE?
LET’S NAME SOME
MOST OF THOSE ARE SERVER DATABASES
None
SQLITE THE STATUS QUO
▸ Single-threaded ▸ Dynamically-typed ▸ Weakly-typed ▸ Designed in 2000
WHAT ARE OUR CONSTRAINTS?
▸ Running on a device ▸ Can’t update database code
on a whim ▸ Little RAM ▸ Relatively few CPU cores ▸ Multiple processes ▸ Long-running use of data
WHAT DO WE WANT TO OPTIMIZE FOR?
▸ Querying ▸ Reading values ▸ Maintainable API ▸ Safe
Migrations ▸ Static + Dynamic Schemas
THE GOALS
▸ Cross-platform ▸ Memory-mapped ▸ Thread-safe ▸ Object-oriented ▸ Blazing
fast ▸ Sane interface
CROSS PLATFORM
People build services that need to run on multiple platforms.
Their database should reflect this.
MEMORY MAPPING
void *mmap( void *addr, size_t length, int prot, int flags,
int fd, off_t offset ); This function is magical.
Blur the line between in-memory and on-disk to get the
best of both worlds. Take advantage of optimizations in the kernel and let it do the hard work for you.
THREAD SAFETY
THREAD SAFETY PERHAPS THE MOST LOADED WORD IN CS
WELL-DEFINED THREADING MODEL ▸ What can be passed between threads?
▸ How easily can I isolate things that can’t be?
Built with speed & safety in mind: ▸ No reader
lock ▸ Allow concurrent reading & writing ▸ Let the user know when they violate the threading contract
OBJECT-ORIENTED API
▸ First-class model objects ▸ Support for persisted + in
memory objects ▸ No invisible web of classes
BLAZING FAST
WHY SHOULD OBJECTS AND THE DATABASE EVER GROW APART?
WHY SHOULD OBJECTS AND THE DATABASE EVER GROW APART? OR
WHERE ORMS WENT WRONG
▸ Lazily create objects in memory ▸ Access & set
values directly in the DB ▸ Optimized query engine
SANE API
▸ What do I need a reference to? ▸ Platform
coherence ▸ Isolate DB interaction ▸ Make it impossible to mess up
LET’S RECAP
▸ Cross-platform ▸ Memory-mapped ▸ Thread-safe ▸ Object-oriented ▸ Blazing
fast ▸ Sane interface
SOUNDS A LOT LIKE THE DREAM, RIGHT?
Make persistence just another aspect of your data, instead of
a whole convoluted system.
⾠ This might not be the approach for everyone. Take
a look at the goals, and see if they align with your own.
My company, Realm, is working towards building a database that
hits these bullet points. I’m not here to sell you on Realm. But building something that mirrors those goals is why we exist.
EXAMPLES?
Available now on Speaker Deck. https://speakerdeck.com/segiddins/whats-in-a-mobile-database
db.objects(Question).map { $0.ask }
SAMUEL GIDDINS REALM.IO @SEGIDDINS