java - MongoDB Java 驱动程序聚合框架使用 $match 和 $text $search 但首先需要 $project

Question

docs注意:

要在 $match 阶段使用 $text，$match 阶段必须是管道的第一个阶段。

一些 JSON 示例:

{"pid":"b00l16vp", "title": "in our time","categories":{"category1":["factual", "arts culture and the media", "history"]}}
{"pid":"b0079mpp", "title": "doctor who", "categories":{"category2":["childrens", "entertainment and comedy", "animation"],"category1":["signed"]}}
{“pid":"b00htbn3"}
{“pid":"b00gdhqw","categories":{"category2":["factual"],"category3":["scotland"],"category4":["lifestyle and leisure", "food and drink"],"category1":["entertainment", "games and quizzes"]}}

我有以下查询:

    List<BasicDBObject> pipeline = new ArrayList<>()
            BasicDBObject criteria = new BasicDBObject()
            BasicDBObject theProjections = new BasicDBObject()
            AggregateIterable iterable

    //value is coming from a parameter
        if (value != null) {
    //a text index has been created on the title field
            criteria.put('$text', new BasicDBObject('$search', value))

        }
//cats is coming from a parameter but it will be an array of Strings
if (cats.length != 0) {

            ArrayList<BasicDBObject> orList = new ArrayList<>()
            ArrayList<BasicDBObject> andList = new ArrayList<>()
            BasicDBList theMegaArray = new BasicDBList()


            for (int i = 1; i <= 5; i++) {

                String identifier = "categories.category" + i
                String cleanIdentifier = '$' + identifier
                //If the category does not exist, put in a blank category
                theMegaArray.add(new BasicDBObject('$ifNull', Arrays.asList(cleanIdentifier, Collections.EMPTY_LIST)))
            }
//merges all of the category arrays into 1
            theProjections.put("allCategories", new BasicDBObject('$setUnion', theMegaArray))
            orList.add(new BasicDBObject("allCategories", new BasicDBObject('$all', cats)))

            andList.add(new BasicDBObject('$or', orList))
            criteria.put('$and', andList)
        }
    pipeline.add(new BasicDBObject('$project', theProjections))
    pipeline.add(new BasicDBObject('$match', criteria))


    //and by default
    iterable = collection.aggregate(pipeline)

问题是，如果我想搜索猫，我需要首先将投影放在管道中，但如果我想要文本，那么我需要先将匹配放在管道中。有什么办法可以两者兼得吗？

Answer 1

这毕竟是一个非常简单的解决方案。

我创建了一个新的条件对象

BasicDBObject criteriaCat = new BasicDBObject()

添加了类别，而不是原来的标准。

criteriaCat.put('$and', andList)

将 $match 首先放入管道中，然后放入 $project，如果有猫，则再次对结果运行 $match。

 pipeline.add(new BasicDBObject('$match', criteria))
        pipeline.add(new BasicDBObject('$project', theProjections))

        if (cats.length != 0) {
            pipeline.add(new BasicDBObject('$match', criteriaCat))
        }
        pipeline.add(new BasicDBObject('$sort', sorting))

        //and by default
        iterable = collection.aggregate(pipeline)