又在 Coursera 里面选了门课坑自己

最近又学了很多东西,其中记不住的做笔记记下来,这篇文章是为 Ruby on Rails 运用 MongoDB 做准备。

基础命令

Mac 下安装 MongoDB 可以参考 Mac下使用brew安装mongodb

启动数据库

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% mongod

进入命令行模式

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% mongo

导入 MongoDB 提供的示例数据

示例数据下载

在 json 文件所在的文件夹下导入数据库。

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% mongoimport --db test --collection zips --drop --file zips.json

irb Shell 中的一些基础操作

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irb
2.3.3 :001 > require 'mongo'
=> true
2.3.3 :002 > db = Mongo::Client.new('mongodb://localhost:27017')
D, [2017-02-16T00:06:03.651134 #39047] DEBUG -- : MONGODB | Topology type 'unknown' initializing.
D, [2017-02-16T00:06:03.651314 #39047] DEBUG -- : MONGODB | Server localhost:27017 initializing.
D, [2017-02-16T00:06:03.654477 #39047] DEBUG -- : MONGODB | Topology type 'unknown' changed to type 'single'.
D, [2017-02-16T00:06:03.654581 #39047] DEBUG -- : MONGODB | Server description for localhost:27017 changed from 'unknown' to 'standalone'.
D, [2017-02-16T00:06:03.654674 #39047] DEBUG -- : MONGODB | There was a change in the members of the 'single' topology.
=> #<Mongo::Client:0x70333621287660 cluster=localhost:27017>
2.3.3 :003 > db = db.use('test')
=> #<Mongo::Client:0x70333622110940 cluster=localhost:27017>
2.3.3 :004 > db.database.name
=> "test"
2.3.3 :005 > db.database.collection_names
D, [2017-02-16T11:11:07.299786 #39047] DEBUG -- : MONGODB | localhost:27017 | test.listCollections | STARTED | {"listCollections"=>1, "cursor"=>{}, "filter"=>{:name=>{"$not"=>/system\.|\$/}}}
D, [2017-02-16T11:11:07.326259 #39047] DEBUG -- : MONGODB | localhost:27017 | test.listCollections | SUCCEEDED | 0.025663000000000002s
=> ["zips"]
2.3.3 :006 > db[:zips].find.first
D, [2017-02-16T11:12:51.044213 #39047] DEBUG -- : MONGODB | localhost:27017 | test.find | STARTED | {"find"=>"zips", "filter"=>{}}
D, [2017-02-16T11:12:51.059517 #39047] DEBUG -- : MONGODB | localhost:27017 | test.find | SUCCEEDED | 0.015213s
=> {"_id"=>"01001", "city"=>"AGAWAM", "loc"=>[-72.622739, 42.070206], "pop"=>15338, "state"=>"MA"}

Win 系统下可以用 system('cls') 命令来清空 irb shell
Mac OS X 和 Linux 系统可以用 Ctrl + L 来清空屏幕

精简输出

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2.3.3 :008 > Mongo::Logger.logger.level = ::Logger::INFO
=> 1
2.3.3 :009 > db[:zips].find.first
=> {"_id"=>"01001", "city"=>"AGAWAM", "loc"=>[-72.622739, 42.070206], "pop"=>15338, "state"=>"MA"}

Create and Read

介绍 CRUD 增查改删操作的前两步操作

“C”reate

  • Select a collection on the client and call insert_one or insert_many
  • insert_one: insert one document to collection
  • insert_many: insert multiple documents to the collection

insert_one

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db[:zips].insert_one(:_id => "100",:city => "city01", :loc => [ -76.05922700000001, 39.564894], :pop => 4678,:state => "MD")

用 find 和 count 来搜索数据

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db[:zips].find(:city => "city01").count

插入一项数据,并且测试该项数据的存在

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2.3.3 :010 > db[:zips].insert_one(:_id => "100",:city => "city01", :loc => [ -76.05922700000001, 39.564894], :pop => 4678,:state => "MD")
=> #<Mongo::Operation::Result:70333617635280 documents=[{"n"=>1, "ok"=>1.0}]>
2.3.3 :011 > db[:zips].find(:city => "city01").count
=> 1
2.3.3 :012 > db[:zips].find(:city => "city01").to_a
=> [{"_id"=>"100", "city"=>"city01", "loc"=>[-76.059227, 39.564894], "pop"=>4678, "state"=>"MD"}]

insert_many

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db[:zips].insert_many([
{ :_id => "200", :city => "city02",
:loc => [ -74.05922700000001, 37.564894 ],
:pop => 2000, :state => "CA" },
{ :_id => "201", :city => "city03",
:loc => [ -75.05922700000001, 35.564894 ],
:pop => 3000, :state => "CA" }
])

同时插入多项数据

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2.3.3 :013 > db[:zips].insert_many([
2.3.3 :014 > { :_id => "200", :city => "city02",
2.3.3 :015 > :loc => [ -74.05922700000001, 37.564894 ],
2.3.3 :016 > :pop => 2000, :state => "CA" },
2.3.3 :017 > { :_id => "201", :city => "city03",
2.3.3 :018 > :loc => [ -75.05922700000001, 35.564894 ],
2.3.3 :019 > :pop => 3000, :state => "CA" }
2.3.3 :020?> ])
=> #<Mongo::BulkWrite::Result:0x007fefa58136d8 @results={"n_inserted"=>2, "n"=>2, "inserted_ids"=>["200", "201"]}>
2.3.3 :021 > db[:zips].find("city" => "city02").to_a
=> [{"_id"=>"200", "city"=>"city02", "loc"=>[-74.059227, 37.564894], "pop"=>2000, "state"=>"CA"}]
2.3.3 :022 > db[:zips].find("city" => "city03").to_a
=> [{"_id"=>"201", "city"=>"city03", "loc"=>[-75.059227, 35.564894], "pop"=>3000, "state"=>"CA"}]

“R”ead

  • find command
  • find – returns a cursor object – allows us to iterate over the selected document(s)
  • Can be used with query criteria
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# basic find
db[:zips].find(:city => "BALTIMORE")
# find first
db[:zips].find.first
db[:zips].find(:state => "MD").first
# find with double conditions and count them
db[:zips].find(:state => "NY", :city => "GERMANTOWN").count
# find distinct
db[:zips].find.distinct(:state)

使用 pp (pretty-printing) 来美化命令行的输出,并且找到符合条件的第一项

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2.3.3 :035 > require 'pp'
=> true
2.3.3 :036 > pp db[:zips].find(:state => "NY", :city => "GERMANTOWN").first
{"_id"=>"12526",
"city"=>"GERMANTOWN",
"loc"=>[-73.862451, 42.1219],
"pop"=>4061,
"state"=>"NY"}
=> {"_id"=>"12526", "city"=>"GERMANTOWN", "loc"=>[-73.862451, 42.1219], "pop"=>4061, "state"=>"NY"}

Cursor Iterations

print all

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db[:zips].find().each { |r| puts r }

pretty printing

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require 'pp'
db[:zips].find().each { |r| pp r }

Projection

  • Limits the fields to return from all matching documents
  • We can specify inclusion or exclusion.
  • _id is automatically included by default.
  • true or 1: inclusive
  • false or 0: exclusive

限制返回项的输出,例如只输出 state 属性,_id 是默认输出的,我们也可以取消输出 _id 项。

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2.3.3 :040 > db[:zips].find({:state => "MD"}).projection(state:true).first
=> {"_id"=>"20331", "state"=>"MD"}
2.3.3 :041 > db[:zips].find({:state => "MD"}).projection(state:true, _id:false).first
=> {"state"=>"MD"}

Paging

  • Paging is accomplished with skip and limit
  • skip(n) - tells mongodb that it should skip ‘n’ results
  • limit(n) - instructs mongodb that it should limit the result length to ‘n’ results

limit

限制搜索只有三项输出

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2.3.3 :044 > db[:zips].find.limit(3).each{ |r| pp r}
{"_id"=>"01001",
"city"=>"AGAWAM",
"loc"=>[-72.622739, 42.070206],
"pop"=>15338,
"state"=>"MA"}
{"_id"=>"01002",
"city"=>"CUSHMAN",
"loc"=>[-72.51565, 42.377017],
"pop"=>36963,
"state"=>"MA"}
{"_id"=>"01005",
"city"=>"BARRE",
"loc"=>[-72.108354, 42.409698],
"pop"=>4546,
"state"=>"MA"}
=> #<Enumerator: #<Mongo::Cursor:0x70333637935980 @view=#<Mongo::Collection::View:0x70333616708020 namespace='test.zips' @filter={} @options={"limit"=>3}>>:each>

skip

跳过前三项,显示后三项

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2.3.3 :045 > db[:zips].find.skip(3).limit(3).each { |r| pp r}
{"_id"=>"01007",
"city"=>"BELCHERTOWN",
"loc"=>[-72.410953, 42.275103],
"pop"=>10579,
"state"=>"MA"}
{"_id"=>"01008",
"city"=>"BLANDFORD",
"loc"=>[-72.936114, 42.182949],
"pop"=>1240,
"state"=>"MA"}
{"_id"=>"01010",
"city"=>"BRIMFIELD",
"loc"=>[-72.188455, 42.116543],
"pop"=>3706,
"state"=>"MA"}
=> #<Enumerator: #<Mongo::Cursor:0x70333639364960 @view=#<Mongo::Collection::View:0x70333639398700 namespace='test.zips' @filter={} @options={"skip"=>3, "limit"=>3}>>:each>

Sort

sort - Specifies the order in which the query returns matching documents.

{ field: value }

1 for Ascending, -1 for Descending.

搜索后以城市名升序输出,若改为{:city => -1 }则为逆序输出。

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2.3.3 :046 > db[:zips].find.limit(3).sort({:city => 1 }).each { |r| pp r}
{"_id"=>"42601",
"city"=>"AARON",
"loc"=>[-85.199114, 36.812827],
"pop"=>270,
"state"=>"KY"}
{"_id"=>"16820",
"city"=>"AARONSBURG",
"loc"=>[-77.387977, 40.876944],
"pop"=>100,
"state"=>"PA"}
{"_id"=>"31794",
"city"=>"ABAC",
"loc"=>[-83.498867, 31.451722],
"pop"=>27906,
"state"=>"GA"}
=> #<Enumerator: #<Mongo::Cursor:0x70333639793460 @view=#<Mongo::Collection::View:0x70333626982300 namespace='test.zips' @filter={} @options={"limit"=>3, "sort"=>{"city"=>1}}>>:each>

Advanced Find

Find By Criteria

  • ‘lt’ & ‘gt’
  • Evaluations
  • Regex
  • Exists
  • Not
  • Type

lt and gt

lt -> less than
gt -> great than

找到城市名比「P」小的,且比「B」大的三项

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2.3.3 :049 > db[:zips].find(:city => {:$lt => 'P', :$gt => 'B'}).limit(3).to_a.each { |r| pp r};nil
{"_id"=>"01002",
"city"=>"CUSHMAN",
"loc"=>[-72.51565, 42.377017],
"pop"=>36963,
"state"=>"MA"}
{"_id"=>"01005",
"city"=>"BARRE",
"loc"=>[-72.108354, 42.409698],
"pop"=>4546,
"state"=>"MA"}
{"_id"=>"01007",
"city"=>"BELCHERTOWN",
"loc"=>[-72.410953, 42.275103],
"pop"=>10579,
"state"=>"MA"}
=> nil

小 Tips:
我们已经用 pp 来格式化输出了,可以在语句结尾加;nil来精简额外的输出,如上所示。

Regex

Regex – supports regular expression capabilities for pattern matching strings in queries.

用正则表达式匹配城市名含有 X 的项

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2.3.3 :052 > db[:zips].find(:city => {:$regex => 'X'}).limit(3).each {|r| pp r};nil
{"_id"=>"01240",
"city"=>"LENOX",
"loc"=>[-73.271322, 42.364241],
"pop"=>5001,
"state"=>"MA"}
{"_id"=>"01537",
"city"=>"NORTH OXFORD",
"loc"=>[-71.885953, 42.16549],
"pop"=>3031,
"state"=>"MA"}
{"_id"=>"01540",
"city"=>"OXFORD",
"loc"=>[-71.868677, 42.11285],
"pop"=>9557,
"state"=>"MA"}
=> nil

X& :Displays cities ending with X
^X :Displays cities starting with X
^[A- E] :Displays cities that match the regex (A to E)

$exist

Will check to see of the document exists when the boolean is true

mongo 中的 documents 可能会没有一些 values,我们可以用$exist来找出存在相关 values 的项。

找出 :city 属性不为空的三项

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2.3.3 :053 > db[:zips].find(:city => {:$exists => true}).projection({:_id => false}).limit(3).to_a.each {|r| pp r}
{"city"=>"AGAWAM", "loc"=>[-72.622739, 42.070206], "pop"=>15338, "state"=>"MA"}
{"city"=>"CUSHMAN", "loc"=>[-72.51565, 42.377017], "pop"=>36963, "state"=>"MA"}
{"city"=>"BARRE", "loc"=>[-72.108354, 42.409698], "pop"=>4546, "state"=>"MA"}
=> [{"city"=>"AGAWAM", "loc"=>[-72.622739, 42.070206], "pop"=>15338, "state"=>"MA"}, {"city"=>"CUSHMAN", "loc"=>[-72.51565, 42.377017], "pop"=>36963, "state"=>"MA"}, {"city"=>"BARRE", "loc"=>[-72.108354, 42.409698], "pop"=>4546, "state"=>"MA"}]

$not

$not performs a logical NOT operation
Selects the documents that do not match the

找到 :pop 属性不大于9500的项

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2.3.3 :012 > db[:zips].find(:pop =>{'$not' => {'$gt' => 9500}}).projection({_id:false}).limit(3).to_a.each {|r| pp r};nil
{"city"=>"BARRE", "loc"=>[-72.108354, 42.409698], "pop"=>4546, "state"=>"MA"}
{"city"=>"BLANDFORD",
"loc"=>[-72.936114, 42.182949],
"pop"=>1240,
"state"=>"MA"}
{"city"=>"BRIMFIELD",
"loc"=>[-72.188455, 42.116543],
"pop"=>3706,
"state"=>"MA"}
=> nil

$type

$type - selects the documents where the value of the field is an instance of the specified numeric BSON type.

简而言之,$type的作用就是验证相关属性的类型。这在我们不知道数据类型的时候很好用,我们可以在 BSON Types 页面中查看各数字代表着什么,例如 1 代表 Double 类型,2 代表 String 类型。

在下面示例中,:state 属性应是 String 类型,所以 :&type => 2 会有结果。:&type => 1没有结果,是因为 :state 不是 Double 类型。

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2.3.3 :014 > db[:zips].find({:state=> {:$type => 2}}).first
=> {"_id"=>"01001", "city"=>"AGAWAM", "loc"=>[-72.622739, 42.070206], "pop"=>15338, "state"=>"MA"}
2.3.3 :015 > db[:zips].find({:state=> {:$type => 1}}).first
=> nil

Replace, Update and Delete

介绍 Replace 和 CRUD 的后两项操作

  • replace_one
  • update_one
  • update_many
  • delete_one
  • delete_many
  • upsert

Replace

replace_one

replace_one – Replace a document in the collection according to the specified parameters.

替换:_id => "101"项的所有信息

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2.3.3 :017 > db[:zips].insert_one(:_id => "101", :city => "citytemp", :loc => [ -76.05922700000001, 39.564894 ], :pop => 4678, :state => "MD" )
=> #<Mongo::Operation::Result:70126374694180 documents=[{"n"=>1, "ok"=>1.0}]>
2.3.3 :018 > db[:zips].find(:_id =>"101").replace_one(:_id => "101", :city => "city02", :loc => [ -78.22, 36.22 ], :pop => 2000, :state => "MD" )
=> #<Mongo::Operation::Result:70126384942080 documents=[{"n"=>1, "nModified"=>1, "ok"=>1.0}]>
2.3.3 :019 > db[:zips].find(:_id => "101").to_a
=> [{"_id"=>"101", "city"=>"city02", "loc"=>[-78.22, 36.22], "pop"=>2000, "state"=>"MD"}]

“U”pdate

update_one

update_one – Update a single document in the collection according to the specified arguments.

只更新单项中的属性,例如改城市名或同时更改多个属性

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2.3.3 :022 > db[:zips].find(:_id => "101").update_one(:$set => {:city => "name2"})
=> #<Mongo::Operation::Result:70126374531300 documents=[{"n"=>1, "nModified"=>1, "ok"=>1.0}]>
2.3.3 :023 > db[:zips].find(:_id => "101").to_a
=> [{"_id"=>"101", "city"=>"name2", "loc"=>[-78.22, 36.22], "pop"=>2000, "state"=>"MD"}]
2.3.3 :024 > db[:zips].find(:_id => "101").update_one(:$set => {:city => "name3", :loc => [ 11.11, 11.11 ]})
=> #<Mongo::Operation::Result:70126373842240 documents=[{"n"=>1, "nModified"=>1, "ok"=>1.0}]>
2.3.3 :025 > db[:zips].find(:_id => "101").to_a
=> [{"_id"=>"101", "city"=>"name3", "loc"=>[11.11, 11.11], "pop"=>2000, "state"=>"XX"}]

update_many

update_many – Updates single or multiple documents in the collection according to the specified arguments.

更新多项属性,例如把所有州名为MD的项中的州名更改为XX

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2.3.3 :026 > db[:zips].find(:state => 'MD').count
=> 422
2.3.3 :027 > db[:zips].find(:state => 'MD').update_many(:$set => {:state => 'XX'})
=> #<Mongo::Operation::Result:70126374300980 documents=[{"n"=>422, "nModified"=>422, "ok"=>1.0}]>
2.3.3 :028 > db[:zips].find(:state => 'MD').count
=> 0
2.3.3 :029 > db[:zips].find(:state => 'XX').count
=> 422

“D”elete

delete_one

delete_one – will delete a single document in the collection according to the specified arguments.

删除之前添加的城市名为 name3 的项

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2.3.3 :005 > db[:zips].find(:city => 'name3').count
=> 1
2.3.3 :006 > db[:zips].find(:city => 'name3').delete_one()
=> #<Mongo::Operation::Result:70293222869840 documents=[{"n"=>1, "ok"=>1.0}]>
2.3.3 :007 > db[:zips].find(:city => 'name3').count
=> 0

delete_many

delete_many – deletes single or multiple documents in the collection according to the specified arguments.

删除所有州名为XX的项

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2.3.3 :009 > db[:zips].find(:state => 'XX' ).count
=> 421
2.3.3 :010 > db[:zips].find(:state => 'XX' ).delete_many()
=> #<Mongo::Operation::Result:70293222986380 documents=[{"n"=>421, "ok"=>1.0}]>
2.3.3 :011 > db[:zips].find(:state => 'XX' ).count
=> 0

upsert

If upsert is true and no document matches the query criteria, update() inserts a single document.

如果把 upsert (更新插入)设为 true,即使没有找到相关的项(条件不满足),也会执行 update_one来创建一个项

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2.3.3 :014 > db[:zips].find(:city => "ODENVILLE1").count
=> 0
2.3.3 :015 > db[:zips].find(:city => "ODENVILLE2").count
=> 0
2.3.3 :016 > db[:zips].find(:city =>"ODENVILLE1").update_one({:$set => {:city => "ODENVILLE2"}}, :upsert => true)
=> #<Mongo::Operation::Result:70293217700720 documents=[{"n"=>1, "nModified"=>0, "upserted"=>[{"index"=>0, "_id"=>BSON::ObjectId('58a5746b62b11bdc607226a8')}], "ok"=>1.0}]>
2.3.3 :017 > db[:zips].find(:city => "ODENVILLE1").count
=> 0
2.3.3 :018 > db[:zips].find(:city => "ODENVILLE2").count
=> 1
2.3.3 :019 > db[:zips].find(:city => "ODENVILLE2").to_a
=> [{"_id"=>BSON::ObjectId('58a5746b62b11bdc607226a8'), "city"=>"ODENVILLE2"}]