This document discusses Realm, a mobile database solution that provides an alternative to SQLite. Realm aims to be faster than SQLite by using techniques like memory mapping, column orientation, and bit packing. It offers both an object-oriented query interface and a SQL-like query interface. Realm addresses common issues with SQLite like slow queries, changing schemas, and complex relationships.

1. 1
X y
- Queries too slow
- Schemas change
- Complex relationships
- 3NF, BCNF…
- Nest SELECT, JOIN
- 1-n, 1-1, n-n
- Migration
- Synchonize
- Huge records
- …
SQLite problems

2. REALM
khacpv@gmail.com
15/05/2016
no-sqlite for mobile

3. Who am I?
3

4. Realm is
SQL
SELECT user.name, user.email
FROM user
INNER JOIN shop ON user.id = shop.userid
INNER JOIN city ON user.cityid = city.id
WHERE user.name = 'the flash'
No-SQL
Realm.getA().getC().getF();
A
B C
D E F
G
X
Z
y
4

5. Realm is
SQLite
SELECT user.name, user.email
FROM user
INNER JOIN shop ON user.id = shop.userid
INNER JOIN city ON user.cityid = city.id
WHERE user.name = 'khac'
No-SQLite
Realm.getA().getC().getF();
A
B C
D E F
G
X
Z
y
5

6. YOUR
logo?
6

7. How: fastest?
7

8. Galaxy S4
8

9. Zenfone 5
9

10. Why: fastest?
10

11. Speed force
• Memory-mapped files
• C++ core
• B+ trees
• Column-oriented
• Bit-packing
Minimize I/O overhead
Cross-platform
Faster reads and writes
Queries > writes (no-sql)
Smaller file size
11

12. benchmark vs SQLite
http://static.realm.io/downloads/java/android-benchmark.zip 12

13. Architecture
Realm Object Store API
Realm Internal API
JNI
Realm Core
13

14. Method count
• Realm: ~1750
• Model class: +2x no. of fields
• Proxy class: + 2x no. of fields + 11
• Total: "it depends" (~2000)
Picasso: ~600
GSON: ~950
RxJava: ~3500
Retrofit: ~494
Support Lib: ~12300
OrmLite: ~2400
14

15. How: code?
15

16. get Realm
16
web:
version:
support:
contributors:
last release:
https://realm.io
0.90.1
xamarin, java, obj-c, swift, react-native
52+ (java)
7 days ago (13/05/2016)
classpath "io.realm:realm-gradle-plugin:0.90.1"
apply plugin: 'realm-android'
ProGuard!

17. Realtime
17
update realtime

18. Types fields
18
@Required
@Ignore
@RealmClass
@Index
@PrimaryKey
boolean
byte, short,int,long -> long
float
double
String
Date
byte[]
final
transient
volatile

19. Relationships
19
n…1
n…n

20. Queries
20
• equalTo
• greaterThan
• between
• contains
• beginWith
• beginGroup
• or
• not
• isEmpty
• distinct
• sum/ count
• min/ max/ average
• findAll/ findFirst
• sort
• …

21. Insert / Update
21

22. Delete
22

23. Configuration
23
1. Encrypt with key (AES-256)
2. Migration strategy
3. In memory mode
4. Default instance
5. isAutoRefresh() & waitForChange()
6. Create from JSON
https://nelenkov.blogspot.dk/2012/05/storing-application-secrets-in-androids.html
https://developer.android.com/training/articles/keystore.html

24. Thread
Realm
Realm
object
Realm
Results
Threads
24
RealmObject
A B C
Not yet Polymorphism

25. Debug
25
Crashlytics

26. Limitations
26
1. Class names: <= 57 letters*
2. Field names: <= 63 letters
3. Nest transactions -> not supported!
4. String & byte[] < 16Mb
*Realm auto append class_ at begin of class name

27. References
• https://realm.io/news/introducing-realm
• https://realm.io/users/chatwork
• https://github.com/realm
• http://www.slideshare.net/ChristianMelchior/realm-building-a-
mobile-database
• http://www.slideshare.net/dalinaum/realm-java
• https://en.wikipedia.org/wiki/Zero-copy
• https://en.wikipedia.org/wiki/Data_structure_alignment
27

28. Q & A
28

29. • Why do you choose Realm?
• Faster 5~10 times, especialy in write data
• Combine with ActiveAndroid
• Which data should be stored in Realm?
• The data need to be writen many times, ex: total
chats.
• Should remove ActiveAndroid to only play with Realm.
• Yes, it’s doesn’t complicated but ActiveAndroid has
value too.
• Easy to synchronize with data from server
• Yes, no problem
• Use for both Android & Ios?
• Yes
29
ChatWork
Ryutaro Miyashita
https://realm.io/users/chatwork/

30. 30
Appendix

31. B+ Tree
31https://en.wikipedia.org/wiki/B%2B_tree
The primary value of a B+ tree is in storing data for
efficient retrieval in a block-oriented storage context in
particular, filesystems. (NTFS, EXT4, SQLite, Oracle …

32. Column Oriented
32http://arxiv.org/pdf/1105.4252.pdf

33. Memory-mapped
33
Memory-mapped I/O uses the same address bus to
address both memory and I/O devices
CPU
RAM
Hard Disk
I/O
https://en.wikipedia.org/wiki/Memory-mapped_file

34. http://www.slideshare.net/jpountz/how-does-lucene-store-your-data
http://lemire.me/blog/2012/03/06/how-fast-is-bit-packing/
Bit-packing
34
• Efficient technique to store blocks of small ints
• Supports random access
• Special case: bits per value = 1 is a bit set
• Say you want to store
• 5 30 1 1 10 12
• Raw data: 6 * 32 = 192 bits
• Packed : 6 * 5 = 30 bits (84% size reduction!)
0000 0000 0000 0000 0000 0000 0000 0101 = 5
0000 0000 0000 0000 0000 0000 0001 1110 = 30
0000 0000 0000 0000 0000 0000 0000 0001 = 1
0000 0000 0000 0000 0000 0000 0000 0001 = 1
0000 0000 0000 0000 0000 0000 0000 1010 = 10
0000 0000 0000 0000 0000 0000 0000 1100 = 12