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This article will explain in detail how to embed Javascript in MongoDBRuby. The content of the article is of high quality, so the editor shares it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

How to embed Javascript in MongoDBRuby

Class Publication

Include Mongoid::Document

Field: name,: type = > String

Field: section,: type = > String

Field: body,: type = > String

Field: is_published,: type = > Boolean

End

Class LongerPublication

Field: extra_body,: type = > String

End

At this point, a Publication class and a LongerPublication class already exist in the system. Now we need to do some work on information collection, and we want to get statistics on the number of Publication class objects by their type and state. In addition, it is best to carry out targeted statistical analysis according to the current state.

One way is to use Mongo's built-in map-reduce. Mongoid extends this functionality, allowing programmers to use Ruby programs to implement the inline Javascript functions (mapper and reducer) they need. Readers may think this method is not good, but it seems to be the best way so far. There are many more complex functions that write these Javascript functions into separate files, which may be easier to test, but readers who test the input / output of this work themselves will find that their performance is not good.

How to embed Javascript in MongoDBRuby

KLASS = "this._type"

SECTION = "this.section"

Def self.count_by (type)

Map =

< 　　function() { 　　function truthy(value) { 　　return (value ==true) ?1 :0; 　　} 　　emit(#{type}, {type: #{type}, count:1, published: truthy(this.is_published)}) 　　} 　　EOF 　　reduce = < 　　function(key, values) { 　　var count =0; published =0; 　　values.forEach(function(doc) { 　　count += parseInt(doc.count); 　　published += parseInt(doc.published); 　　type = doc.type 　　}; 　　return {type: type, count: count, published: published} 　　} 　　EOF 　　collection.mapreduce(map, reduce).find() 　　end 　　在进行实验测试时会返回类似如下代码所示的数据;不过有些读者在实验时也有可能返回Mongo::Cursor，通过Mongo::Cursor可以获取到以下数据。 　　[{"_id"=>

"Publication", "value" = > {"type" = > "Publication", "count" = > 42.0, "published" = > 29.0}}

{"_ id" = > "LongerPublication", "value" = > {"type" = > "LongerPublication", "count" = > 12.0, "published" = > 10.0}}]

Mongo and Mongoid make me like the mapreduce work of this kind of information collection very much, especially the mixing of Ruby and Javascript programming languages without affecting the readability of the code. Given a relational database, users are likely to write all kinds of strange SQL statements-- because the syntax differences between Javascript and SQL are much smaller than those between any other language and Ruby.

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