mongodb-schema

mongodb-schema

Infer a probabilistic schema for a MongoDB collection.

A high-level view of the class interactions is as follows:

Example

mongodb-schema doesn't do anything directly with mongodb so to try the examples we'll install the node.js driver.
As well, we'll need some data in a collection to derive the schema of.

Make sure you have a mongod running on localhost on port 27017 (or change the example accordingly). Then, do:

• npm install mongodb mongodb-schema
• mongo --eval "db.test.insert([{_id: 1, a: true}, {_id: 2, a: 'true'}, {_id: 3, a: 1}, {_id: 4}])" localhost:27017/test
• Create a new file parse-schema.js and paste in the following code:

var parseSchema = require('mongodb-schema');
var connect = require('mongodb');

connect('mongodb://localhost:27017/test', function(err, db){
  if(err) return console.error(err);

  parseSchema('test.test', db.collection('test').find(), function(err, schema){
    if(err) return console.error(err);

    console.log(JSON.stringify(schema, null, 2));
    db.close();
  });
});

• When we run the above with node parse-schema.js, we'll see something like the following (some fields not present here for clarity):

{
  "count": 4,                   // parsed 4 documents
  "ns": "test.test",            // namespace
  "fields": [                   // an array of Field objects, @see `./lib/field.js`
    {
      "name": "_id",
      "count": 4,               // 4 documents counted with _id
      "type": "Number",         // the type of _id is `Number`
      "probability": 1,         // all documents had an _id field
      "unique": 4,              // 4 unique values found
      "has_duplicates": false,  // therefore no duplicates
      "types": [                // an array of Type objects, @see `./lib/types/`
        {
          "name": "Number",     // name of the type
          "count": 4,           // 4 numbers counted
          "probability": 1,
          "unique": 4,
          "values": [           // array of encountered values
            1,
            2,
            3,
            4
          ]
        }
      ]
    },
    {
      "name": "a",
      "count": 3,               // only 3 documents with field `a` counted
      "probability": 0.75,      // hence probability 0.75
      "type": [                 // found these types
        "Boolean",
        "String",
        "Number",
        "Undefined"             // for convenience, we treat Undefined as its own type
      ],
      "unique": 3,
      "has_duplicates": false,   // there were no duplicate values
      "types": [
        {
          "name": "Boolean",
          "count": 1,
          "probability": 0.25,  // probabilities for types are calculated factoring in Undefined
          "unique": 1,
          "values": [
            true
          ]
        },
        {
          "name": "String",
          "count": 1,
          "probability": 0.25,
          "unique": 1,
          "values": [
            "true"
          ]
        },
        {
          "name": "Number",
          "count": 1,
          "probability": 0.25,
          "unique": 1,
          "values": [
            1
          ]
        },
        {
          "name": "Undefined",
          "count": 1,
          "probability": 0.25,
          "unique": 0
        }
      ]
    }
  ]
}

More Examples

mongodb-schema supports all BSON types. Checkout the tests for more usage examples.

Installation

npm install --save mongodb-schema

Testing

npm test

License

Apache 2.0

Contributing

Under the hood, mongodb-schema uses ampersand-state and ampersand-collection for modeling Schema, Field's, and Type's.