node.js + async series execution

Question

In my node app i am using async.series for executing 3 queries its executed very well.. But in my 3rd query execution i have to execute another query based on result of 3rd query its also working fine. But t i executing some logic in the third query so after all gets completed only i have to call callback....

My code:

async.series({
    levels: function(cb) {
        sequelize.query("select country_id, country_name, level0, level1, level2, level3, level4 from levels").success(function(levelsResults) {
            levelsResult = levelsResults;
            cb(null, levelsResult);
        })
    },
    level1: function(cb) {
        sequelize.query("select id_0, name_0, name_1 from xxxxx group by id_0, name_0, name_1").success(function(level1Result) {
            level1result = level1Result;
            cb(null, level1result);
        })
    },
    keys: function(cb) {
        sequelize.query("select id_0 from xxxx group by id_0").success(function(id_0Result) {
            var obj = {};
            for (var i = 0; i < id_0Result.length; i++) {
                sequelize.query("select id_0, value->>'yyyy' as value from xxxx where id_0 = " + id_0Result[i].id_0 + " limit 1").success(function(keyResult) {
                    var keyArray = [];
                    var keysObjectArray = [];
                    id_0 = keyResult[0].id_0;
                    keyResult = keyResult[0].value;
                    keyResult = JSON.parse(keyResult);

                    for (var prop in keyResult) {
                        keyArray.push(prop)
                    }
                    obj["" + id_0 + ""] = keyArray;
                    keysObjectArray.push(obj);
                    cb(null, keysObjectArray);
                    ---.my problem is here cb is called in the 1st iteration of
                    for loop.It should be called after loop finishes

                })
            }
        })
    }
}, function seriesFinal(seriesErr, seriesResults) {
    if (seriesErr) throw new Error("Something bad!");
    onSuccess(JSON.stringify(seriesResults), callback);

});

My result is:

{"levels":[{levsls}],"level1":[{level1}],"keys":[{}]};

but what i am expecting is:

{"levels":[{levsls}],"level1":[{level1}],"keys":[{},{}]};

EDIT:

Simply how can i make the sequlize query to execute for loop and finally have to call the callback

Help me to solve this..Thanks in advance.....

Yooz · Accepted Answer · 2014-04-09 05:05:00Z

The "for" loop runs "n" queries which callbacks randomly the "success" function.

You can use a counter to make sure that all your queries called back

sequelize.query("select id_0 from xxxx group by id_0").success(function(id_0Result){
                var obj = {};
                var counter = 0;
                for(var i=0; i<id_0Result.length; i++){
                    sequelize.query("select id_0, value->>'yyyy' as value from xxxx where id_0 = "+id_0Result[i].id_0+" limit 1").success(function(keyResult){
                            var keyArray=[];
                            var keysObjectArray =[];
                            id_0 = keyResult[0].id_0;                                
                            keyResult = keyResult[0].value;
                            keyResult = JSON.parse(keyResult);

                            for (var prop in keyResult){
                                keyArray.push(prop)
                            }                                
                            obj[""+id_0+""] = keyArray;                                
                            keysObjectArray.push(obj);   
                            counter  +=1;
                            if(counter === id_0Result.length )
                            {                             
                               cb(null, keysObjectArray);
                            }

                    })
                }

Note that the order in keysObjectArray is random as are the callbacks.

Hope it helps.

Yoann

sgress454 · Accepted Answer · 2014-04-09 05:17:43Z

1

There's more to async than just async.series! You can use async.forEach to do loops, and for your keys function, async.map will do nicely:

keys: function(cb) {                   
    sequelize.query("select id_0 from xxxx group by id_0").success(function(id_0Result){
        var obj = {};
        // Loop over each object in id_0Result, 
        // and transform it into a new array
        async.map(
            id_0Result, 
            function(result, cb) {
                sequelize.query("select id_0, value->>'yyyy' as value from xxxx where id_0 = "+result.id_0+" limit 1").success(function(keyResult){
                    var keyArray=[];
                    id_0 = keyResult[0].id_0;                                
                    keyResult = keyResult[0].value;
                    keyResult = JSON.parse(keyResult);

                    for (var prop in keyResult){
                        keyArray.push(prop)
                    }                                
                    obj[""+id_0+""] = keyArray;
                    // Add this object to the array result for async.map
                    return cb(null, obj);
                })
            }, 
            // Call the callback for async.series with the result of
            // the mapping; effectively cb(null, transformedArray)
            cb
        );
    });
}

answered Apr 9, 2014 at 5:17

sgress454

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1 Comment

Subburaj Over a year ago

Thanks @Scott Gress ..i have 1 more doubt.. i have an object array is it possible to make key value pair by taking id_0 from my object,i think async.map will help me..

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