mongodb aggregate: Convert Aggregate Result To Collection

carc.js

/*
 convertAggregateResultToCollection (alias: carc)
 Author: Ronald Stalder <[email protected]>
*/

var convertAggregateResultToCollection = function (aggResult, options) {
    
    // void function to supress output
    var _v = function() {};
    
    // SET DEFAULT OPTIONS UNLESS SPECIFIED
    // options = {
    //
    //     "out"  : name of the resulting collection, default: "out"
    //
    //     "mode" : "replace" eventually existing "out" or create new one
    //                        (default, will drop the collection first, 
    //                                  then same as "append") 
    //              "append"  to existing collection using insert (see "key")
    //              "merge"   into existing collection using update-upsert on key
    //
    //     "key"  : <field>   use this field as "_id" for the documents
    //                        in the "out" collection
    //                        If the option "removeKey" is true, the <field> will 
    //                        be "renamed" to _id, by default it will be copied
    //
    //              "objId"   an existing "_id" field in the result will be renamed 
    //                        to the value of the "renameKey" option,
    //                        or deleted if "removeKey" is true,
    //                        in order to force the generation of an objectId
    //
    //              "_id"     Default behavior is to take the "_id" from the result.
    //                        If it does not exist, an ObecjtId will automatically be 
    //                        generated (this will result in "merge" being an "append")       
    //
    //     "removeKey" : true or false, default=false. See above
    //
    //     "renameKey" : (string) existing "_id" in the result will be renamed to this
    //                            (see above). Default: "origId"
    //
    //     "constFields" :   array of {name:"name", value:"value"} pairs - default: empty array
    //                       In the resuling document, a "name": value field will be
    //                       inserted for each pair in this array
    //
    //     "debug": 0 - (default) quiet
    //              1 - print out some basic information
    //              2 - print out some stuff for debugging
    //              3 - print also the result of the aggregate
    // }    
    
    if ( typeof options == 'undefined' ) var options = {};
    if ( typeof options.out == 'undefined' ) options.out = "out";
    if ( typeof options.mode == 'undefined' ) options.mode = "replace";
    if ( typeof options.key == 'undefined' ) options.key = "_id";
    if ( typeof options.removeKey == 'undefined' ) options.removeKey = false;
    if ( typeof options.renameKey == 'undefined' ) options.renameKey = "origId";
    if ( typeof options.constFields == 'undefined' ) options.constFields = [];
    if ( typeof options.debug == 'undefined' ) options.debug = 0;
    var debug = options.debug;

    if ( debug ) print ( "\n*** convertAggregateResultToCollection (carc) -- start\n" );
    if ( debug > 2 ) printjson( aggResult );
    if ( debug > 1 ) printjson( options );
    
    // check for valid aggregate result in first parameter
    if ( typeof aggResult.result !== "object" ) {
        print( "ERROR: first parameter must be a valid output of aggregate() !\nexitting function" );
        return false;
    }
    try { _v(aggResult.result[0]) }
    catch(err) {
        print( "ERROR: output of aggregate() is empty\nexitting function" );
        return false;
    }
    
    // set the output collection
    var out = db.getCollection( options.out );
    if ( debug ) print( 'output collection: "' + out + '" output mode is: "'+options.mode+'"' );
    // drop it if in "replace" mode and switch to "append"
    if ( options.mode === "replace" ) {
        out.drop();
        options.mode = "append";
        if ( debug ) print( 'output collection dropped; switched to "append" mode' );
    }
    
    var r = aggResult.result;
    
    // DETERMINE _ID FOR OUT COLLECTION
    // asking for _id but there isn't any: switch to "objId"
    var txt = 'the "_id" of the resulting documents will be ';
    if ( options.key === "_id" && typeof r[0]._id === "undefined" ) {
        if ( debug > 1 ) print( 'no _id in result, using "objectId"' );
        options.key = "objId";
    }
    
    // as a generated objectId
    if ( options.key === "objId" ) {
        if ( debug ) print( txt+'a generated objectId' );
    
    // from a field in the result
    } else {
        eval( "var _idField = r[0]."+options.key );
        var _idType = typeof _idField;
        // check that given key field exists
        if ( options.key !== "_id" && _idType === "undefined" ) {
            print( "ERROR: given key field '"+options.key
                   +"' does not exist\nexitting function" );
            return false;
        }
        if ( debug ) {
            if ( _idType === "object" ) {
                print( txt+"the compound:");
                printjson( _idField );
            } else {
                print( txt+"the key: "+_idField );
            }
        }
    }
    
    // LOOP THE RESULTS AND CREATE THE DOCUMENTS
    if ( debug ) print( 'processing ' + r.length + ' result records' );
    for ( var i in aggResult.result ) {
        
        doc = aggResult.result[i];
        
        // set _id
        if ( !(options.key === "_id" || options.key === "objId") ) {
            // copy the key <field> to _id
            eval( "_idField = doc."+options.key );
            doc._id = _idField;
            // and eventually remove it
            if ( options.removeKey ) delete _idField;
        // if we want objectId and there is an existing _id
        } else if ( options.key === "objId" 
                    && typeof doc._id !== 'undefined' ) {
            // rename the _id, unless the removeKey option is set to true
            if ( !options.removeKey ) eval( "doc."+options.renameKey+" = doc._id" );
            // delete the _id, so an objectId will be generated
            delete doc._id;
        }
        
        // add constant Fields
        for ( var j in options.constFields ) {
            eval( "doc."+options.constFields[j].name+"='"+options.constFields[j].value+"'" );
        }
        
        // insert or update-upsert
        if ( options.mode === "append" ) {
            out.insert( doc );
        } else {
            // prepare update command for the "merge"
            var updCmd = 'out.update({"_id":doc._id},{$set:{';
            // update set all field from the result
            for ( var key in doc ) {
                if ( key == "_id" ) continue;
                updCmd += '"'+key+'": "'+doc[key]+'",' 
            }
            updCmd += '}},{"upsert":true})';
            // execute it
            eval( updCmd );
        }
        if ( debug > 1 ) printjson( doc );
    }
    
    if ( debug ) print ( "\n*** convertAggregateResultToCollection (carc) -- end\n" );
}

// set the alias
var carc = convertAggregateResultToCollection;