在dynamodb中获取关系数据

Question

I have studied many articles and blogs and finally conclude that I need only one base table for whole application and then many Global Secondary Indexes according to my access patterns. Now I have stuck in a problem.

My base table structure is:-

**PK** **SK** **data**

university uni_uuid name

course course_uuid uni_uuid

As you see when I will add a new course it will always have a university uuid which will save under university_uuid key with course record.

Now I want to list all the courses to Admin. So I query the dynamodb like:-

var params = {
      TableName: "BaseTable",
      FilterExpression:"PK = :type",
      ExpressionAttributeValues: {
          ":type": "Course"
      }
  };

  docClient.scan(params, onScan);
  var count = 0;

  function onScan(err, result) {
      if (err) {
          console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2));
      } else {        
          resolve(result);
      }
  }

This successfully returns me all the added courses. Like:-

Now my question is that how can I show University name in the column University. Currently university_uuid is displaying here. Do I need to run another query and find university name by its uuid, if so then for 100 courses I need to run 100 more queries for each course university name.

Any help will deeply appreciated!!

Answer 1

Approaches:

1. If university name will not be changed in Admin you can use denormalization and include it into courses table. Even if university name can be changed, on update you can get all corresponded courses by uni_uuid and update redundant data.
2. When you receive courses list, distinct uni_uuid and then request data from universities using IN clouse.