MongoDB Live Hacking Preparations

01_mongodb_live_hacking.md

Download & Run MongoDB

• Grab the latest stable release from the download page
• Unzip the archive to a folder called ${MONGO_HOME} on your disk
• Create a folder /data/db on the same drive/partition
• Go to ${MONGO_HOME}/bin
• Execute the binary mongod (or mongod.exe on Windows)

For a more detailed explanation, see the MongoDB installation guide.

Import Test Data

Before we start, we need some test data.

• Start the MongoDB shell by exectuing mongo
• Paste the code from 02_geospatial.js into the shell
• Paste the code from 03_map_reduce.js into the shell

01b_crud_queries.js

// dbs
show dbs
use oops
show collections

// insert data
db.foo.insert({a: 1, b: "zwei"})
// show mongod console -> oop.ns oop.0 oop.1

db.foo.find()
db.foo.insert({a: 2, b: "drei"})
db.foo.find()
db.foo.insert({a: -1, b: "fünf"})

// queries
db.foo.find({a: {$gt: 1}})
db.foo.find({a: {$gt: 1}}, {_id:0}) // restrict fields

// index
db.foo.find({a:2}).explain()
db.foo.ensureIndex({a:1})
db.foo.find({a:2}).explain()
db.system.indexes.find()
db.system.namespaces.find()

// limit + sort
db.foo.find().limit(2)
db.foo.find().sort({a:-1})
db.foo.find().sort({a:-1}).limit(2)
db.foo.find().sort({a:-1}).limit(2).explain()

// update
db.foo.find()
db.foo.update( {a:1}, {b:"vier"}) // ersetzt Dokument komplett
db.foo.find()
db.foo.update({a:2}, {$set: {b: "sechs"}})
db.foo.find()

// upsert
db.foo.update({a:5}, {$inc: {a:1}}, true)
db.foo.find()

// remove
db.foo.remove({a: {$lt: 0}})
db.foo.find()

// drop
db.foo.drop()

02_geospatial.js

db.location.remove()
db.location.insert({ "_id" : "A", "position" : [ 0.001, -0.002 ] })
db.location.insert({ "_id" : "B", "position" : [ 0.75, 0.75 ] })
db.location.insert({ "_id" : "C", "position" : [ 0.5, 0.5 ] })
db.location.insert({ "_id" : "D", "position" : [ -0.5, -0.5 ] })
db.location.ensureIndex( {position: "2d"} )

02b_geospatial.js

// blue circle
db.location.find( {position: { $near: [0,0], $maxDistance: 0.75 }  } )

// smaller circle
db.location.find( {position: { $near: [0,0], $maxDistance: 0.5 }  } )

// red box
db.location.find( {position: { $within: { $box: [ [0.25, 0.25], [1.0,1.0] ]  } } } )

03_map_reduce.js

db.docs.remove()
db.docs.insert({ "name" : "Doc 1", "tags" : [ "cc", "mongodb", "nosql" ] } )
db.docs.insert({ "name" : "Doc 2", "tags" : [ "cc", "agile" ] } )
db.docs.insert({ "name" : "Doc 3", "tags" : [ "cc", "nosql" ] } )

map = function () {
    this.tags.forEach(function (tag) {emit(tag, 1);});
};
reduce = function (key, values) {
    return values.length;
};

db.result.remove()
db.docs.mapReduce(map, reduce, {out: "result"})

db.result.find()
db.result.find().sort({value:-1})

04_aggregation.js

// since 2.2 -> aggregation framework
db.docs.aggregate( 
   {$project:{_id:0,tags:1}}, 
   {$unwind: "$tags"}, 
   {$group:{_id:"$tags", n:{$sum:1}}} 
)

db.docs.aggregate( 
   {$project:{_id:0,tags:1}}, 
   {$unwind: "$tags"}, 
   {$group:{_id:"$tags", n:{$sum:1}}}, 
   {$sort:{n:-1}} 
)

05_text_search.js

// enable text search
use admin
db.runCommand( {setParameter:1, textSearchEnabled: true} )
use txt

// create text index
db.txt.drop()
db.txt.ensureIndex( {txt: "text"} )
db.txt.getIndices()

// insert data
db.txt.insert( {txt: "I am your father, Luke"} )
db.txt.validate()

// search
db.txt.runCommand( "text", { search : "father" } )

50_replica_set.sh

start mongod --port 8000 --dbpath /var/rs/master --replSet cluster0
start mongod --port 8001 --dbpath /var/rs/slave1 --replSet cluster0
start mongod --port 8002 --dbpath /var/rs/slave2 --replSet cluster0

51_master.js

// connect to master on port 8000 + setup replica set
rs.initiate()
rs.add("localhost:8001")
rs.add("localhost:8002")

// use primary: mongo --port 8000
rs.isMaster()
rs.status()
use test
db.foo.insert({hello: "mongo"})

// use secondary: mongo --port 8001
rs.isMaster()
use test
db.foo.insert({hello: "mongo"})
db.foo.find()

60_sharding.sh

start mongod --shardsvr --port 9000 --dbpath /var/sh/shard1
start mongod --shardsvr --port 9001 --dbpath /var/sh/shard2
start mongod --configsvr --port 9002 --dbpath /var/sh/conf1
pause
start mongos --port 9003 --configdb localhost:9002 --chunkSize 2

61_init_sharding.js

use admin
sh.addShard("localhost:9000")
sh.addShard("localhost:9001")
sh.status()

use data
db.createCollection("foo")

use admin
sh.enableSharding("data")
sh.shardCollection("data.foo", {age:1})
sh.status()

// insert some data
use data
for (i=0; i<1000000;i++) { db.foo.insert( {name:"Person_"+i, age: 50 + i%20} ); }

62_search_shards.js

// connect to mongos instance

use data
sh.status()

// hits all shards -> bad
db.foo.find().limit(100).explain()

// using sharding hits only one shard -> good
db.foo.find({age:51}).limit(100).explain()