RegularIndexesVsMultiKey.js

// compares MongoDB regular Indexes vs using MultiKey & Elematch

/* // regular index: 
{ "field0": 0,
  "field1": 1,
  "field2": 2 ... etc }
  
MultiKey index: 
{ "props": [
    { "field": "field0", "value": 0 },
    { "field": "field1", "value": 1 },
    { "field": "field2", "value": 2 },
    .. etc ] }   */

function compareIndexes(numFields,numDocuments) {
    db=db.getSiblingDB("testIndexes");
    db.dropDatabase()
    var counter = 0;

    //create regular indexes
    for(i=0;i<numFields;i++){
        indexdoc = {}
        indexdoc["field"+i]=1
        db.regular.ensureIndex(indexdoc);
    }

    //create multikey index
    db.fancy.ensureIndex({"props.field":1,"props.value":1});

    //create regular document
    var start = new Date().getTime();
    for(j=0;j<numDocuments;j++){ 
        var doc = { }
        for(i=0;i<numFields;i++){
            doc["field"+i]=counter++
        }
        db.regular.insert(doc);
    }
    var regularInsertTime=new Date().getTime()-start;

    //query regular document 
    counter = 0
    var start = new Date().getTime();
    for(j=0;j<numDocuments;j++){ 
        var resultf = db.regular.findOne({field0:counter});
        counter = counter + numFields; 
    }
    var regularFindTime=new Date().getTime()-start;

    //create fancy array thingamajigs whatchamacallit
    counter = 0;
    var start = new Date().getTime();
    for(j=0;j<numDocuments;j++){
        var doc = [ ]
        for(i=0;i<numFields;i++){
            doc.push({field: "field"+i, value: counter++})
        }
        db.fancy.insert({"props":doc});
    }
    var fancyInsertTime=new Date().getTime()-start;

    //query fancy document  
    counter = 0
    var start = new Date().getTime();
    for(j=0;j<numDocuments;j++){ 
        var resultf = db.fancy.findOne({props:{$elemMatch:{"field":"field0","value":counter}}})
        counter = counter + numFields; 
    }
    var fancyFindTime=new Date().getTime()-start;

    //compile results
    result={numFields:numFields,numDocuments:numDocuments, 
            regular: {insertTime: regularInsertTime,
                       indexSize: db.regular.stats().totalIndexSize,
                       findTime: regularFindTime},
            fancy: { insertTime: fancyInsertTime,
                      indexSize: db.fancy.stats().totalIndexSize,
                      findTime: fancyFindTime }
            } 
    return result;
}

//run tests various index and doc size combinations
for(docs=1000;docs<1000001;docs=docs*10){
    for(indexes=1;indexes<64;indexes=indexes+3){
        print("Testing with: \tIndexes: " + indexes + "\tDocs: " + docs ) 
        result = compareIndexes(indexes,docs)
        db.getSiblingDB("indexTest").results.insert(result);
    }
}


//print results, insert
for(indexes=1;indexes<64;indexes=indexes+3){
    var string = "Indexes, " + indexes + ",";
    for(docs=1000;docs<1000001;docs=docs*10){
        res = db.getSiblingDB("indexTest").results.findOne({numFields:indexes,numDocuments:docs});
        if(res != null){ 
            var regular = res.regular.findTime;
            var fancy = res.fancy.findTime;
            var slowdown = (fancy+regular)/(regular)
            string = string + slowdown + ","
        } else {
            string = string + 0 + ","
        }
    }
    print(string)
}

//print results, query 
for(indexes=1;indexes<64;indexes=indexes+3){
    var string = "Indexes, " + indexes + ",";
    for(docs=1000;docs<1000001;docs=docs*10){
        res = db.getSiblingDB("indexTest").results.findOne({numFields:indexes,numDocuments:docs});
        if(res != null){ 
            var regular = res.regular.insertTime;
            var fancy = res.fancy.insertTime;
            var slowdown = (fancy+regular)/(regular)
            string = string + slowdown + ","
        } else {
            string = string + 0 + ","
        }
    }
    print(string)
}


//print results, query 
for(indexes=1;indexes<64;indexes=indexes+3){
    var string = "Indexes, " + indexes + ",";
    for(docs=1000;docs<1000001;docs=docs*10){
        res = db.getSiblingDB("indexTest").results.findOne({numFields:indexes,numDocuments:docs});
        if(res != null){ 
            var regular = res.regular.indexSize;
            var fancy = res.fancy.indexSize;
            var slowdown = (fancy+regular)/(regular)
            string = string + slowdown + ","
        } else {
            string = string + 0 + ","
        }
    }
    print(string)
}