DynamoDB 查询二级索引，如何定义索引

Question

我一直在纠结这个问题，只是不清楚该怎么做。

我有一个简单的 table，我想在其中对多个列进行查询。据我了解，这意味着为每个要查询的列创建一个二级索引。我已经定义了 table——使用无服务器框架 serverless.yml——并且收到了各种奇怪的错误消息。

当前的serverless.yml定义是：

resources:
  Resources:
    MessagesDynamoDBTable:
      Type: 'AWS::DynamoDB::Table'
      Properties:
        AttributeDefinitions:
          - AttributeName: messageId
            AttributeType: S
          - AttributeName: room
            AttributeType: S
          - AttributeName: userId
            AttributeType: S
        KeySchema:
          - AttributeName: messageId
            KeyType: HASH
          - AttributeName: userId
            KeyType: RANGE
        LocalSecondaryIndexes:
          - IndexName: roomIndex
            KeySchema: 
              - AttributeName: room
                KeyType: HASH
            Projection: 
              ProjectionType: "KEYS_ONLY"
          - IndexName: userId
            KeySchema: 
              - AttributeName: userId
                KeyType: HASH
            Projection: 
              ProjectionType: "KEYS_ONLY"
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:custom.tableName}

它应该类似于 Slack 服务 - 因此我想查询来自房间、用户等的条目。

根据我能找到的文档，这个定义很有意义。应该为索引中使用的列声明属性，我已经这样做了。 KeySchema - 我真的只需要 messageId 字段，但一条错误消息表明它需要一个 RANGE 索引，所以我将 userId 字段添加到 KeySchema 只是为了关闭它。根据我能够找到的文档，二级索引字段看起来是正确的。

使用此定义，我在尝试使用 serverless deploy

进行部署时遇到此错误

An error occurred: MessagesDynamoDBTable - Property AttributeDefinitions is inconsistent 
with the KeySchema of the table and the secondary indexes.

我尝试了几种变体，也遇到了其他奇怪的错误。下面是一些，但我不记得相应的定义有什么变化。

An error occurred: MessagesDynamoDBTable - One or more parameter values were invalid: 
Index KeySchema does not have a range key for index: userId (Service: AmazonDynamoDBv2; Status Code: 400;
Error Code: ValidationException; Request ID: 1KFA2IMASC12HRLLDPG753CU63VV4KQNSO5AEMVJF66Q9ASUAAJG).

An error occurred: MessagesDynamoDBTable - 1 validation error detected: Value '[com.amazonaws.dynamodb.v20120810.KeySchemaElement@aa4cdc91, 
com.amazonaws.dynamodb.v20120810.KeySchemaElement@d2cd6f64, com.amazonaws.dynamodb.v20120810.KeySchemaElement@4d7c1f9, 
com.amazonaws.dynamodb.v20120810.KeySchemaElement@d2cd6f64]' at 'keySchema' failed to satisfy constraint: Member must have length less
 than or equal to 2 (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException; Request ID: BOVVBQ1F35VA18CCF3L5MSKS1FVV4KQNSO5AEMVJF66Q9ASUAAJG).

An error occurred: MessagesDynamoDBTable - Property AttributeDefinitions is inconsistent with the KeySchema 
of the table and the secondary indexes.

An error occurred: MessagesDynamoDBTable - One or more parameter values were invalid: Index KeySchema does not have a range key for index:
 userIdIndex (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException; Request ID: KFS63VSPKDUC60DV6U2V47UP27VV4KQNSO5AEMVJF66Q9ASUAAJG).

An error occurred: MessagesDynamoDBTable - One or more parameter values were invalid: Table KeySchema does not have a range key,
 which is required when specifying a LocalSecondaryIndex (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException; Request ID: 86Q2JSPM6Q9UPNIEOVHALLIIQJVV4KQNSO5AEMVJF66Q9ASUAAJG).

Answer 1

它不起作用的原因是本地二级索引中的键必须与 table 具有相同的分区键。因此，在您的情况下，您的本地二级索引必须将 messageId 作为其 HASH 键，并且将 room 和 userId 作为其各自索引上的 RANGE 键。由于您的 table 已经由 (messageId, userId) 键入，因此您不需要 userId Local Secondary Index。

此设置在技术上可行：

MessagesDynamoDBTable:
  Type: AWS::DynamoDB::Table
  Properties:
    AttributeDefinitions:
      - AttributeName: messageId
        AttributeType: S
      - AttributeName: room
        AttributeType: S
      - AttributeName: userId
        AttributeType: S
    KeySchema:
      - AttributeName: messageId
        KeyType: HASH
      - AttributeName: userId
        KeyType: RANGE
    LocalSecondaryIndexes:
      - IndexName: roomIndex
        KeySchema:
          - AttributeName: messageId
            KeyType: HASH
          - AttributeName: room
            KeyType: RANGE
        Projection:
          ProjectionType: KEYS_ONLY
    ProvisionedThroughput:
      ReadCapacityUnits: 1
      WriteCapacityUnits: 1
    TableName: ${self:custom.tableName}

但是，如果您想按房间和用户进行查询，那么您可能希望采用不同的 table 设计。您尝试执行的操作最终会要求您始终使用 messageId 查询 table 作为查询的一部分，因为它是分区键。因此，您将无法仅通过 room 和 userId 进行查询。您可能想要的是 Global Secondary Indexes。在那种情况下，这将起作用：

MessagesDynamoDBTable:
  Type: AWS::DynamoDB::Table
  Properties:
    AttributeDefinitions:
      - AttributeName: messageId
        AttributeType: S
      - AttributeName: room
        AttributeType: S
      - AttributeName: userId
        AttributeType: S
    KeySchema:
      - AttributeName: messageId
        KeyType: HASH
    GlobalSecondaryIndexes:
      - IndexName: roomIndex
        KeySchema:
          - AttributeName: room
            KeyType: HASH
        Projection:
          ProjectionType: KEYS_ONLY
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
      - IndexName: userIndex
        KeySchema:
          - AttributeName: userId
            KeyType: HASH
        Projection:
          ProjectionType: KEYS_ONLY
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
    ProvisionedThroughput:
      ReadCapacityUnits: 1
      WriteCapacityUnits: 1
    TableName: ${self:custom.tableName}

请注意，使 ProjectionType: KEYS_ONLY 意味着当您查询 roomIndex 或 userIndex 时，您将得到的只是 messageIds - 然后您将不得不重新查询 table 与 messageIds 以获得其他属性。根据您的使用模式，您可能希望使用不同的 ProjectionType。

DynamoDB 查询二级索引，如何定义索引

DynamoDB queries on secondary index, how to define the indexes

amazon-dynamodb

serverless-framework

dynamodb-queries

amazon-dynamodb-index