使用包含运算符的Dynamo数据库查询

Question

My table items are of the form of

function addDoc(movie,cb){
    var params = {
        TableName: "Movies",
        Item: {
            "year":  movie.year,
            "title": movie.title,
            "info":  movie.info,
            "genres" : movie.info.genres || []
        }
    };
    docClient.put(params, function(err, data) {
        bar.tick(1)
        i++;
        cb(err);
    });
}

async.eachLimit(allMovies,50,addDoc,function (err) {
    console.log(err)
    console.log("done inserting " + i + " movies");
});

I'm running this code :

var params = {
    TableName : "Movies",
    //ProjectionExpression:"#yr, title, genres, info.actors[0]",
    KeyConditionExpression: "#yr = :yyyy and contains(genres, :g1)",
    ExpressionAttributeNames:{
        "#yr": "year"
    },
    ExpressionAttributeValues: {
        ":yyyy":1992,
        ":g1" : "Drama"
    },
    //Select : "COUNT"
};
var start = Date.now()
docClient.query(params, function(err, data) {
    if (err) {
        console.error("Unable to query. Error:", JSON.stringify(err, null, 2));
    } else {
        console.log("time elapsed :",Date.now()-start);
        console.log("Query succeeded.");

        console.log(data)

    }
});

and I'm getting this error

"Invalid operator used in KeyConditionExpression: contains"

any idea?

Answer 1

There are few things that need to be clarified here.

1) The Key attributes of DynamoDB has to be scalar data type. So, I believe the attribute genres can't be defined as SET or LIST data type

2) KeyConditionExpression - can refer to Hash and Sort key only. So, I presume the attribute genres is defined as SORT key of the table

3) contains can be used on FilterExpression on data types STRING, SET or LIST. It can't be used on KeyConditionExpression

Conclusion - Refer point 3 for straight forward answer