Question

我一直在四处走动，而且还不清楚该怎么做。

我有一个简单的表格，我想对多个列进行查询。据我了解，这意味着要为每个列创建一个二级索引来进行查询。我已经使用无服务器框架serverless.yml定义了表格，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}

它意味着像Slack服务 - 因此我想查询来自房间，用户等的条目。

这个定义通过我能够找到的文档来理解。一个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，但是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正确。

根据此定义，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。以下是一些，但我不记得相应的变化对定义的影响。

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

它无法工作的原因是本地二级索引中的键必须与表具有相同的分区键。因此，在您的情况下，您的本地辅助索引必须messageId作为其HASH密钥，room和userId作为RANGE密钥在其各自的索引上。由于您的表格已由(messageId, userId)键入，因此您不需要userId Local Secondary Index。

此设置在技术上有效：

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，如果你想要做的是按房间和用户查询，那么你可能想要使用不同的表格设计。您要做的事情最终会要求您始终使用messageId作为查询的一部分查询表，因为它是分区键。因此，您无法仅通过room和userId进行查询。你可能想要的是Global Secondary Indexes。在这种情况下，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，当您查询ProjectionType: KEYS_ONLY或roomIndex时，userIndex表示您将获得的内容仅为messageIds - 您必须重新查询表格messageIds获取其他属性。您可能希望使用不同的ProjectionType，具体取决于您的使用模式。

DynamoDB查询二级索引，如何定义索引

1 个答案: