Fetching applications, clients, and departments related to a ticket

Question

I have a CouchDB view with the following view/reduce function. After working over 2 hours on it, I have a result I am happy with, but I believe there is a lot of room for improvement. Basically, I would like the code a bit more slim.

map: function (doc) {
    if (doc.type == 'ticket') {
        emit([doc._id, doc.applications, doc.clients, doc.release, doc.departments], doc)
    } else if (doc.type == 'application') {
        emit([doc._id, 0], doc)
    } else if (doc.type == 'client') {
        emit([doc._id, 1], doc)
    } else if (doc.type == 'release') {
        emit([doc._id, 2], doc)
    } else if (doc.type == 'department') {
        emit([doc._id, 3], doc)
    }
}, 
reduce: function (keys, values, rereduce) {
    var result = null
    var applications = []
    var clients = []
    var release
    var departments = []
    for (var i = 0; i < values.length; i++) {
        if (values[i]) {
            if (values[i].type == 'ticket') {
                result = values[i]
            } else if (values[i].type == 'application') {
                applications.push(values[i])
            } else if (values[i].type == 'client') {
                clients.push(values[i])
            } else if (values[i].type == 'release') {
                release = values[i]
            } else if (values[i].type == 'department') {
                departments.push(values[i])
            }
        }
    }
    if (result != null) {
        var apps = []
        var cls = []
        var deps = []
        if (result.applications) {
            for (var i = 0; i < applications.length; i++) {
                if (result.applications.indexOf(applications[i]._id) > -1) {
                    apps.push(applications[i])
                }
            }
        }
        if (result.clients) {
            for (var i = 0; i < clients.length; i++) {
                if (result.clients.indexOf(clients[i]._id) > -1) {
                    cls.push(clients[i])
                }
            }
        }
        if (result.departments) {
            for (var i = 0; i < departments.length; i++) {
                if (result.departments.indexOf(departments[i]._id) > -1) {
                    deps.push(departments[i])
                }
            }
        }
        result.applications = apps
        result.clients = cls
        result.departments = deps
        result.release = release
        return result
    }
}
}

To answer the question, what my code is doing, I have documents in my database, which contain ticket data. These look like this:

{
   "_id": "12345",
   "_rev": "33-bb1ad1ec8429b638f1cb8ec2c592c8f6",
   "priority": "200",
   "description": "Ja, ist was",
   "deadline": "",
   "minutesperweek": "125",
   "ordervolume": "125",
   "impactdescription": "Irgendwas geht nicht mehr",
   "applications": [
       "6817eeda32184183e792011df10013e6"
   ],
   "departments": [
       "966f9e33d4d0233d967e0e3d3a000a90"
   ],
   "type": "ticket",
   "assignee": {
       "_id": "theo",
       "firstname": "Theo",
       "lastname": "Test",
       "emailaddress": "[email protected]",
       "phonenumber": "123456"
   },
   "assigneehistory": [
       {
           "_id": "theo",
           "firstname": "Theo",
           "lastname": "Test",
           "emailaddress": "[email protected]",
           "phonenumber": "123456"
       }
   ],
   "comments": [
       {
           "commentvalue": "asd",
           "creator": {
               "_id": "theo",
               "firstname": "Theo",
               "lastname": "Test",
               "emailaddress": "[email protected]",
               "phonenumber": "123456"
           },
           "created": "2014-11-27T15:03:00.342Z"
       }
   ],
   "clients": [
       "1152b87a2c7650ba9f8a7992b10009a1",
       "1152b87a2c7650ba9f8a7992b1000c4e"
   ],
   "reviewcomment": [
       {
           "commentvalue": "fdg",
           "creator": {
               "firstname": "Theo",
               "_id": "test",
               "lastname": "Test",
               "emailaddress": "[email protected]",
               "phonenumber": "123456"
           },
           "created": "2014-12-02T13:50:47.218Z"
       }
   ],
   "reviewed": true
}

With the posted reduce function I would like to replace the arrays of clients, applications and departments with the items from the database. I think that the reduce is not very efficient.

Answer 1

The mapping function can be a lot simpler, i.e.:

map: function (doc) {
    if (doc.type == 'ticket') {
        emit([doc._id, doc.applications, doc.clients, doc.release, doc.departments], doc);
        return;
    }

    var types = ['application', 'client', 'release', 'department'];
    var index = types.indexOf(doc.type);
    if (index != -1)
        emit([doc._id, index], doc);
},

The return isn't strictly necessary, but it's better to exit early anyway.

Now for the reducing function you can again make use of a bit of indirection to reduce the number of lines. I'd also recommend lodash or any other functional library to get rid of the loops, but I guess that is a matter of taste.

I've also always remove as many layers of nesting as possible to keep the code readable, so by using return, continue, or break at the earliest convenience.

So kind of like the following:

reduce: function (keys, values, rereduce) {
    var result = null;
    var release;

    var sequences = {
        application: [],
        client: [],
        department: []
    };

    for (var i = 0; i < values.length; i++) {
        var value = values[i];

        if (!value)
            continue;

        var type = value.type;

        if (type == 'ticket')
            result = value;
        else if (type == 'release')
            release = value;
        else {
            var types = ['application', 'client', 'department'];
            var index = types.indexOf(doc.type);
            if (index != -1)
                sequences[type].push(values[i]);
        }
    }

    if (!result)
        return;

    var apps = [];
    var cls = [];
    var deps = [];

    ...
}

Answer 2

Interesting question,

first off, you have a few jshint problems:

• Finish your lines with semicolons
• Declare i only once in your function
• Avoid null, count on undefined
• You are not using keys
• You are not using rereduce

Beyond this,

• You could generalize the pushing off applications, clients, releases, and departments.
• Instead of using an array with objects with an _id, why not collect the _id values instead in a lookup object, this would be much faster (reduced lookup time) and use less memory.
• You could generalize the lookups off applications, clients, releases, and departments in the 2nd part of the code.

My counter proposal looks like this:

function replaceKeysWithValues(keys, values) {
    for(var i = 0; i < keys.length; i++) {
        keys[i] = values[keys[i]];
    }
}

function reduce(keys, values, rereduce) {
    var lookups = {
            application: {},
            client: {},
            department: {},
            release: {},
        },
        lookupKeys = Object.keys(lookups),
        result, i;
    for(i = 0; i < values.length; i++) {
        values[i] = values[i] || {};
        if(values[i].type == 'ticket') {
            result = values[i];
        } else if(lookupKeys.indexOf(values[i].type) != -1) {
            lookups[values[i].type][values[i]._id] = values[i];
        }
    }
    if(!result) {
        return;
    }
    if(result.applications) {
        replaceKeysWithValues(result.applications, lookups.application);
    }
    if(result.clients) {
        replaceKeysWithValues(result.clients, lookups.client);
    }
    if(result.departments) {
        replaceKeysWithValues(result.departments, lookups.department);
    }
    if(result.releases) {
        replaceKeysWithValues(result.releases, lookups.release);
    }
    return result;
}