How to search and count paths values in MongoDb using java driver

Question

i want to see how many documents I have in a collection with the same base path: my mongoDb is structured like this:

        {
            {_id:1,
             tag1: a, 
             path: C:\Users\A\Downloads\1\qwerty
            }, 
            {
            _id: 2,
            tag1: b,
            path: C:\Users\A\Downloads\2\abcd
            },
            {
             _id: 3, 
            tag1: alfa,
            path: C:\Users\A\Documents\3\fsdf
            },
            {
            _id: 4,
            tag1: beta,
            path: C:\Users\A\Documents\4\aaa
            }
        }

I want to search, for example, how many elements there are in C:\\Users\\A\\Downloads and how many elements there are in C:\\Users\\A\\Documents. How can I do it?

Answer 1

i want to see how many documents I have in a collection with the same base path:

Assuming you are supplying the base path to find the number of documents with that base path - the following regex query will count all the documents with the path field value staring with "C:\\Users\\A\\Downloads\\".

db.paths.find( { path: /^C:\\Users\\A\\Downloads\\/ } ).count()

Code Using MongoDB Java Driver:

Pattern p = Pattern.compile("^C:\\\\Users\\\\A\\\\Documents\\\\");
Bson queryFilter = regex("path", p);
long count = collection.countDocuments(filter);

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The following is the data I am using; there are 4 documents. When I run the code I get a count of 2 (which is correct and expected as there are two paths which match the pattern "^C:\\\\Users\\\\A\\\\Documents\\\\").

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Using the same data as shown in the Compass screenshot, the following aggregation

db.paths.aggregate( [ { $group : { _id : "Counts", Documents: { $sum: { $cond: [ { $regexMatch: { input: "$path" , regex: /^C:\\\\Users\\\\A\\\\Documents\\\\/ } }, 1, 0 ] } }, Downloads: { $sum: { $cond: [ { $regexMatch: { input: "$path" , regex: /^C:\\\\Users\\\\A\\\\Downloads\\\\/ } }, 1, 0 ] } } } }, ] )

prints:

 { "_id" : "Counts", "Documents" : 2, "Downloads" : 1 }

The Java code for the above aggregation:

 Pattern docPattern = Pattern.compile("^C:\\\\\\\\Users\\\\\\\\A\\\\\\\\Documents\\\\\\\\"); Pattern downloadPattern = Pattern.compile("^C:\\\\\\\\Users\\\\\\\\A\\\\\\\\Downloads\\\\\\\\"); List<Bson> pipeline = Arrays.asList(new Document("$group", new Document("_id", "Counts") .append("document_counts", new Document("$sum", new Document("$cond", Arrays.asList( new Document("$regexMatch", new Document("input", "$path") .append("regex", docPattern)), 1L, 0L ) ) ) ) .append("download_counts", new Document("$sum", new Document("$cond", Arrays.asList( new Document("$regexMatch", new Document("input", "$path") .append("regex", downloadPattern)), 1L, 0L ) ) ) ) ), project(excludeId()) ); List<Document> results = new ArrayList<>(); collection.aggregate(pipeline).into(results); results.forEach(System.out::println);

The result document:

 Document{ { document_counts=2, download_counts=1 } }