A NoSQL Alternative to Persisting Data in your Android Apps

A NoSQL Alternative
to Persisting Data in
your Android Apps
Priya Rajagopal
@rajagp

About Me
2
• Priya Rajagopal, Ann Arbor, Michigan
• Mobile Developer Advocate, Couchbase
• Organizer, Mobile Monday Ann Arbor
• 18+ years of professional software development
• Long Time iOS Developer *cough cough *
• Over a decade in R&D
• Twitter : @ rajagp

Modern Data
Issues
3
1
Confidential and Proprietary. Do not distribute without Couchbase consent. © Couchbase 2017. All rights reserved.

Security
4

Platform Support
5

Global Scale
6

Peer-to-Peer
7

Offline
8

Data Synchronization
9
1
2
or

Data Conflicts
10
Image Copyright:https://askfortheworld.files.wordpress.com/2013/02/conflict2.jpg

Data Persistence
in Android
11
2

Why should you care?
12
• Creating “offline first” apps
• Airplane mode
• Regions of poor or no network connectivity
• Improve Perceived User Experience / Start up Time
• Prebuilt bundled database
• Caching of semi-static /static data
• No backend to host data / Local only store
• Privacy

Options in Android
13
• SQLite
• Embedded Public Domain SQL Database Engine
• SQLiteOpenHelper class
• Room
• Shared Preferences
• Key-Value Store for small datasets
• Internal Storage
• File System. Persistent or Cached.
• External Storage
• SD cards

SQLite - Impedence Mismatch : Table -> Objects
14

Handling Database Structural Changes
15
• Option 1: Delete the app from Device

Handling Database Structural Changes
16
• Option 2: Silently drop the table
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + this.TABLE_NAME);
onCreate(sqLiteDatabase);
}

Data Migrations : Simple Case
17
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
if (oldVersion < 2) {
String alter_table_add_website = "ALTER TABLE " + this.TABLE_UNIVERSITY +
"ADD COLUMN " + "website" ;
sqLiteDatabase.execSQL(alter_table_add_website);
}
if (oldVersion < 3) {
String alter_table_rename = "ALTER TABLE " + this.TABLE_UNIVERSITY +
"RENAME TO " + "University" ;
sqLiteDatabase.execSQL(alter_table_rename);
}
// Migrate other versions ….
}

Data Migrations : Complicated
18
• Create new Table with desired format
• Transfer content over from old to new Table
• Drop old Table
• Rename new Table
• Recreate indexes

Progressive Migrations
19
Startup Time for Migrations
AppV1
V1
V1 -> V2
mapping
AppV2
V2
AppV3
V3
V2 -> V3
mapping
AppV4
V4
AppV5
V5
V4 -> V5
mapping
AppV6
V6
V5 -> V6
mapping

NoSQL
21
3

What is NoSQL ?
22
• Non Relational
• Unstructured/ Semi-structured
• Scalable
• SQL-type Queries

Four popular NoSQL data models
23
Key-value
Email
advocates@couchbase.c
om
Key Value
Profile {
"name": "A Person",
"location": "Someplace"
}
Logo

Author Column 1Row
Columnar
JK
Rowling
Column 2
Harry Potter and
the Philosopher's
Stone
1997
Title
Year of
release
Harry Potter and
the Chamber of
Secrets
1998
Harry Potter and
the NoSQL
database
2017

Graph
This is
Euler
Priya Shirly
Ann
Jackson
MITMassachusetts
RPI
Went to President
of
Went to
Is in
Lived in

Document
{
"name": "A Person",
"location": "Place",
"team": "Team A",
"interests": "music"
}
{
"name": "A Person",
"location": "Place",
"team": "Team A",
"interests": "music"
}

JSON Data Modeling
Normalized = Reference De-normalized = Embed

NoSQL: Example 1
US Umich.edu
University Of
Michigan US harvard.edu Harvard University -10516645301
{
"type":"university",
"name":"University of Michigan",
"domain":"umich.edu",
"country":"US”
}
{
"name":"Harvard University”,
"domain":"harvard.edu",
"country":"US",
"estDate":-10516645301
}

NoSQL : Example 2
US harvard.edu
Harvard
University
{
"name":"Harvard University",
"domain":"harvard.edu”,
"country":"US",
"estDate":-10516645301
}
-10516645301
(Double)
US harvard.edu Harvard University “1636”
(String)
{
"name":"Harvard University",
"domain":"harvard.edu”,
"country":"US",
"estYear": “1636”
}
String estYear = doc.getString("estYear");
if (estYear != null) {
// Handle case with estYear.
}
else {
Date estDate = doc.getDate("estDate");
if (estDate != null) {
// Handle case with estDate
}
}

NoSQL For
Android :
Couchbase Mobile
31
4

Couchbase Lite
32
Mobile App
Couchbase Lite
Native API
Native Platform
Bindings
JSON
Lite Core Engine
Fleece
SQLite Engine
• Embedded NoSQL Database
• Open Source
• JSON Document Store
• Android, iOS, .NET…
• Community and Enterprise
• Production Release 1.4
• Developer Preview 2.0

Couchbase Mobile Platform: Full Stack Database Platform
33
Couchbase Lite Sync Gateway Couchbase Server
EMBEDDED DATABASE SYNCHRONIZATION DATABASE SERVER
SECURITY
NoSQL Document Style

Getting Started
34
• https://developer.couchbase.com
• Developer Builds

Integrating with your Android Project
35

Creating / Opening a Database
36
// Set Database configuration
DatabaseConfiguration config = new DatabaseConfiguration(context);
File dir = context.getDir("MyData",Context.MODE_PRIVATE);
config.setDirectory(dir);
config.setEncryptionKey( /*encryption key object*/ );
config.setConflictResolver(/*Set custom resolver*/ );
// Create / Open a database with specified name and configuration
database = new Database(DATABASE_NAME, config);

Indexing
37
// Create value index of "type" property
List<Expression> valueProp = new ArrayList<Expression>();
valueProp.add(Expression.property("type"));
database.createIndex(valueProp);
// Create full text search index
List<Expression> ftsProp = new ArrayList<Expression>();
ftsProp.add(Expression.property("overview"));
database.createIndex(ftsProp, IndexType.FullText, new IndexOptions("en",true));

Inserting Document
38
// Create a new document with specified ”props” map
// If Id is not provided, system generates Id
Document document = new Document(id, props);
database.save(document);
Supported Data Types :
• List
• Date
• Map
• Number
• Null
• String
• Blob
Typed Accessors

Deleting Document
39
Document document = database.getDocument(id);
if (document != null) {
database.delete(document);
}

Deleting Document
40
Document document = database.getDocument(id);
if (document != null) {
database.delete(document);
}

Queries
41
Query query = Query.select(SelectResult.all())
.from(DataSource.database(dbMgr.database))
.where((Expression.property("skills").in("music","movies")).and(Expression.property("type").equalTo("
student")))
.groupBy(Expression.property("grade"))
.orderBy(Ordering.property("name").ascending());
try query.explain()
try query.run()

Full Text Search
42
let query = Query.select(SelectResult.expression(Expression.meta().id)))
.from(DataSource.database(database))
.where (Expression.property("overview").match("music”))
.orderBy(Ordering.property("name").ascending());
try query.explain()
try query.run()

Live Queries
43
// Create a liveQuery to fetch all documents from database
query = Query.
select(SelectResult.all()).
from(DataSource.database(dbMgr.database)).
toLive();
// Add a live query listener to continually monitor for changes
query.addChangeListener(new LiveQueryChangeListener() {
@Override
public void changed(LiveQueryChange change) {
ResultSet resultRows = change.getRows();
Result row;
// Iterate over changed rows, corresponding documents and map to University POJO
while ((row = resultRows.next()) != null) {
// Handle changed row
}
}
}) ;
query.run();

Batch Requests
44
db.inBatch(
new Runnable() {
@Override
public void run() {
// Database Operations
}
}
);

Conflict Resolution
45
• Default Conflict Resolver Provided by System
• Conflict Resolver Invoked on Document Save or during replication update
// Set custom conflict resolver
// In Database configuration
config.setConflictResolver(/*Set object that implements the resolver method*/ );
@Override
public ReadOnlyDocument resolve(Conflict conflict) {
// Get revisions in conflict. Select a winner or merge changes to base
ReadOnlyDocument mine = conflict.getMine();
ReadOnlyDocument theirs = conflict.getTheirs();
return mine;
}

Threading
46
• Thread Safe API
• Replicator updates on Background Thread
• Database change notifications on main thread

Replication / Sync
47
// Sync Gateway Endpoint
private final static String SYNC_GATEWAY_URL = "blip://10.0.2.2:4984/mydatabase/";
// Set Replicator Configuration
ReplicatorConfiguration config = new ReplicatorConfiguration(database, new URI(SYNC_GATEWAY_URL));
config.setContinuous(true);
config.setReplicatorType(ReplicatorConfiguration.ReplicatorType.PUSH_AND_PULL);
config.setAuthenticator(new BasicAuthenticator("user","Password"));
config.setChannels( Arrays.asList("userchannel"));
// Start Replicator Configuration with remote Sync Gateway
mPushPull = new Replicator(config);
mPushPull.addChangeListener(this);
mPushPull.start();

Resources
48
• Couchbase Developer Portal
• https://developer.couchbase.com
• Source Code
• https://github.com/couchbaselabs
• https://github.com/couchbase/

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