Read data saved by spark redis using Java

I using spark-redis to save Dataset to Redis. Then I read this data by using Spring data redis:

This object I save to redis:

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Builder
@RedisHash("collaborative_filtering")
public class RatingResult implements Serializable {
    private static final long serialVersionUID = 8755574422193819444L;

    @Id
    private String id;

    @Indexed
    private int user;

    @Indexed
    private String product;

    private double productN;
    private double rating;
    private float prediction;

    public static RatingResult convert(Row row) {
        int user = row.getAs("user");
        String product = row.getAs("product");
        double productN = row.getAs("productN");
        double rating = row.getAs("rating");
        float prediction = row.getAs("prediction");
        String id = user + product;

        return RatingResult.builder().id(id).user(user).product(product).productN(productN).rating(rating)
                .prediction(prediction).build();
    }

}

Save object by using spark-redis:

JavaRDD<RatingResult> result = ...
...
sparkSession.createDataFrame(result, RatingResult.class).write().format("org.apache.spark.sql.redis")
            .option("table", "collaborative_filtering").mode(SaveMode.Overwrite).save();

Repository:

@Repository
public interface RatingResultRepository extends JpaRepository<RatingResult, String> {

}

I can’t read this data have been saved in Redis by using Spring data redis because structure data saved by spark-redis and spring data redis not same (I checked value of keys created by spark-redis and spring data redis are different by using command: redis-cli -p 6379 keys * and redis-cli hgetall $key)

So how to read this data have been saved using Java or by any library in Java?

Answer

The following works for me.

Writing data from spark-redis.

I use Scala here, but it’s essentially the same as you do in Java. The only thing I changed is I added a .option("key.column", "id") to specify the hash id.

    val ratingResult = new RatingResult("1", 1, "product1", 2.0, 3.0, 4)

    val result: JavaRDD[RatingResult] = spark.sparkContext.parallelize(Seq(ratingResult)).toJavaRDD()
    spark
      .createDataFrame(result, classOf[RatingResult])
      .write
      .format("org.apache.spark.sql.redis")
      .option("key.column", "id")
      .option("table", "collaborative_filtering")
      .mode(SaveMode.Overwrite)
      .save()

In spring-data-redis I have the following:

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Builder
@RedisHash("collaborative_filtering")
public class RatingResult implements Serializable {
    private static final long serialVersionUID = 8755574422193819444L;

    @Id
    private String id;

    @Indexed
    private int user;

    @Indexed
    private String product;

    private double productN;
    private double rating;
    private float prediction;

    @Override
    public String toString() {
        return "RatingResult{" +
                "id='" + id + ''' +
                ", user=" + user +
                ", product='" + product + ''' +
                ", productN=" + productN +
                ", rating=" + rating +
                ", prediction=" + prediction +
                '}';
    }
}

I use CrudRepository instead of JPA:

@Repository
public interface RatingResultRepository extends CrudRepository<RatingResult, String> {

}

Querying:

     RatingResult found = ratingResultRepository.findById("1").get();
     System.out.println("found = " + found);

The output:

found = RatingResult{id='null', user=1, product='product1', productN=2.0, rating=3.0, prediction=4.0}

You may notice that the id field was not populated because the spark-redis stored has a hash id and not as a hash attribute.