How to search within a JSON document stored in DynamoDB

Question

There is a DynamoDB table called 'Field', which has 'pageId' and 'config' fields. The 'config' field contains a list of JSON objects.

Field entity

@Data
@DynamoDBTable(tableName = "field")
public class Field{

  @DynamoDBHashKey(attributeName = "pageId")
  private String pageId;
  @DynamoDBAttribute(attributeName = "config")
  private List<Config> config;
}

Config entity

@Data
@DynamoDBDocument
public class Config{
  @DynamoDBAttribute(attributeName = "fieldName")
  private String fieldName;
  @DynamoDBAttribute(attributeName = "fieldType")
  private String fieldType;
}

The JSON representation of the data in DynamoDB.

  {
  "pageId": {
    "S": "page_1"
  },
   "config": {
    "L": [
      {
        "M": {
          "fieldName": {
            "S": "field_name_1"
          },
          "fieldType": {
            "S": "type_2"
          }
        }
      },
      {
        "M": {
          "fieldName": {
            "S": "field_name-2"
          },
          "fieldType": {
            "S": "type_1"
          }
        }
      }
    ]
  }
}

How can I write code to directly filter the records in the 'field' table based on the 'fieldName' property of the 'config' field without fetching all the records and filtering them afterwards?

• javaVersion = 8
• springVersion = '5.1.18.RELEASE'
• springBootVersion = '2.1.6.RELEASE'
• AwsDynamoDBSdk = com.amazonaws:aws-java-sdk-dynamodb:1.11.548

Answer 1

You cannot. This is a limitation of DynamoDB. A common recipe is to combine this with Opensearch which you would populate using DynamoDB streams and a lambda. Here's a blog post on this.

DynamoDB has a limited ability to search data using queries - you can for example use begins_with to filter on the sort key but that's about it.