2. What is MongoDB?
Open source, scalable, high-performance, document-oriented NoSQL Key-Value
ased database.
Features
•
JSON-style document –oriented storage with schema-less
•
B-tree index supported on any attribute
•
Log-based replication for Master/Slave and Replica Set
•
Auto-sharding architecture (via horizontal partition) scales to thousands of no
•
NoSQL-style query
•
Surprising updating behaviors
•
Map/Reduce support
•
GridFS specification for storing large files
•
Developed by 10gen with commercial support
4. Basic concepts in MongoDB
NoSQL MongoDB
Database
Collection
Document
Field
Index
Cursor
Relational DBMS
Database
Relation
Tuple
Column
Index
Cursor
MongoDB
Databases*
Collections*
Documents* Indexes*
Fields*
* means 0 or more objects
Relational DBMS
Databases*
Relations*
Columns* Indexes*
Each document has its own fields
and makes MongoDB schema-
less.
5. CRUD Demo time
Ø
show dbs view existing databases
Ø
use test use database “test”
Ø
db.t.insert({name:’bob’,age:’30’}) insert 30 years bob
Ø
db. t.insert({name:’alice’,gender:’female’}) insert lady alice
Ø
db. t.find() list all documents in
collection t
Ø
db. t.find({name:’bob’},{age:1}) find 1 year old bob
Ø
db. t.find().limit(1).skip(1) find the second document
Ø
db. t.find().sort({name:1}) sort the results with ascend
name
Ø
db. t.find({$or:[{name:’bob’},{name:’tom’}]}) find bob or tom’s documents
Ø
db. t.update({name:’ bob’},{$set:{age:31}}, update all bob’s age to 31
Ø
false,true})
Ø
db.stats() database statistic
Ø
db.getCollectionNames() collections under this db
Ø
db.t.ensureIndex({name:1}) create index on name
Ø
db.people.find({name:“bob"}).explain() explain plan step
8. MongoDB Sharding
ongoDB uses two key operations to facilitate sharding - split and migrate.
plit splits a chunk into two ranges; it is done to assure no one chunk is unusually la
igrate moves a chunk (the data associated with a key range) to another shard.
his is done as needed to rebalance.
plit is an inexpensive metadata operation, while migrate is expensive as large amo
data may be moving server to server.
oth splits and migrates are performed automatically.
ongoDB has a sub-system called Balancer, which monitors shards loads and move
hunks around if it finds an imbalance.
you add a new shard to the system, some chunks will eventually be moved to
at shard to spread out the load.
recently split chunk may be moved immediately to a new shard if the system
edicts that future insertions will benefit from that move.
10. MongoDB Sharding: Briefly
FROM:C TO:N
#Copy Index Definition from C
#Remove existing data in [min~max]
#Clone the data in[min~max] from C
#Ask C to replicate the changes
#Make sure my view is complete and lock
#Get the document’s DiskLoc for sharding
#Trigger the N to sharding in Pull mode
Sequence
#N commit
#Ask N to commit
11. MongoDB Sharding: In Details
FROM TO
Notice: The FROM can be updated/deleted during sharding and TO can catch up in
step 4.
