DynamoDB获取范围键或全局辅助列的单列列表

2 回答

• 0

  Is the only way of doing it scanning the whole table?
  

  -NO，你可以实现GSI来避免它

  Is there a way to do to find the items in Category by querying just the range key?
  

  • 是的，如果你不想扫描整个表，那么你需要创建GSI，它将Category作为Hash . 此GSI本身将充当表，您可以通过传递类别值来查询它 .

  If change Category to a GSI can I find the items that way?
  

  • 是的，您可以使用类别值查询GSI

  I was reading that if you modified change the attribute "Category" to a global secondary index you can return the items for that GSI. But I have not been able to find how to do that.
  

  • 您需要在创建表时创建GSI，示例在您指定的链接中给出，完成后您可以查询该GSI

  参考文献：http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GSI.html

  回复于 2024-04-19T03:46:08+08:00
• 0

  以下是使用GSI创建 Videos 表的示例代码 .

  Create "Videos" table with GSI:-

  @Autowired
      private AmazonDynamoDBClient dynamoDBClient;
  
      public Boolean createTableWithGlobalSecondaryIndex(String tableName) {
  
          CreateTableRequest createTableRequest = null;
  
          DynamoDB dynamoDB = new DynamoDB(dynamoDBClient);
  
          try {
  
              ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<AttributeDefinition>();
              attributeDefinitions.add(new AttributeDefinition().withAttributeName("videoid").withAttributeType("S"));
              attributeDefinitions.add(new AttributeDefinition().withAttributeName("category").withAttributeType("S"));
  
              ArrayList<KeySchemaElement> keySchema = new ArrayList<KeySchemaElement>();
              keySchema.add(new KeySchemaElement().withAttributeName("videoid").withKeyType(KeyType.HASH));
              keySchema.add(new KeySchemaElement().withAttributeName("category").withKeyType(KeyType.RANGE));
  
              // Initial provisioned throughput settings for the indexes
              ProvisionedThroughput ptIndex = new ProvisionedThroughput().withReadCapacityUnits(150L)
                      .withWriteCapacityUnits(150L);
  
              GlobalSecondaryIndex videoCategoryGsi = new GlobalSecondaryIndex().withIndexName("VideoCategoryGsi")
                      .withProvisionedThroughput(ptIndex)
                      .withKeySchema(new KeySchemaElement().withAttributeName("category").withKeyType(KeyType.HASH),
                              new KeySchemaElement().withAttributeName("videoid").withKeyType(KeyType.RANGE))
                      .withProjection(new Projection().withProjectionType(ProjectionType.ALL));
  
              createTableRequest = new CreateTableRequest().withTableName(tableName).withKeySchema(keySchema)
                      .withAttributeDefinitions(attributeDefinitions)
                      .withProvisionedThroughput(
                              new ProvisionedThroughput().withReadCapacityUnits(100L).withWriteCapacityUnits(100L))
                      .withGlobalSecondaryIndexes(videoCategoryGsi);
  
              Table table = dynamoDB.createTable(createTableRequest);
  
              table.waitForActive();
  
          } catch (ResourceInUseException re) {
  
              if (re.getErrorMessage().equalsIgnoreCase("Cannot create preexisting table")) {
                  LOGGER.info("Table already exists =============>" + tableName);
              } else if (re.getErrorMessage().contains("Table already exists")) {
                  LOGGER.info("Table already exists =============>" + tableName);
                  LOGGER.info("Message =============>" + re.getErrorCode() + ";" + re.getErrorMessage());
              } else {
  
                  throw new RuntimeException("DynamoDB table cannot be created ...", re);
              }
  
          } catch (Exception db) {
  
              throw new RuntimeException("DynamoDB table cannot be created ...", db);
  
          }
  
          return true;
  
      }
  

  Query GSI by category:-

  这里输入只是类别，它是使用GSI查询 . 换句话说，它也不是扫描整个表格 .

  public List<String> findVideosByCategoryUsingGlobalSecondaryIndex(String category) {
  
          List<String> videoAsJson = new ArrayList<>();
  
          DynamoDB dynamoDB = new DynamoDB(dynamoDBClient);
  
          Table table = dynamoDB.getTable("Videos");
  
          Index index = table.getIndex("VideoCategoryGsi");
  
          ItemCollection<QueryOutcome> items = null;
  
          QuerySpec querySpec = new QuerySpec();
  
          querySpec.withKeyConditionExpression("category = :val1")
                  .withValueMap(new ValueMap()
                          .withString(":val1", category));
          items = index.query(querySpec);
  
          Iterator<Item> pageIterator = items.iterator();
  
  
          while (pageIterator.hasNext()) {
              String videoJson = pageIterator.next().toJSON();
              System.out.println("Video json ==================>" + videoJson);
              videoAsJson.add(videoJson);
          }
  
          return videoAsJson;
  
      }
  

  回复于 2024-04-19T03:46:08+08:00