# DynamoDB용 PartiQL에서 트랜잭션 수행 이 단원에서는 DynamoDB용 PartiQL에서 트랜잭션을 사용하는 방법을 설명합니다. PartiQL 트랜잭션은 총 100개의 명령문(작업)으로 제한됩니다. DynamoDB 트랜잭션에 대한 자세한 내용은 [DynamoDB Transactions를 사용하여 복잡한 워크플로 관리](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/transactions.html)를 참조하세요. **참고** 전체 트랜잭션은 읽기 또는 쓰기 문으로 구성해야 합니다. 하나의 트랜잭션에서 두 가지를 모두 혼용할 수는 없습니다. EXISTS 함수는 예외입니다. [TransactWriteItems](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/transaction-apis.html#transaction-apis-txwriteitems) API 작업의 `ConditionCheck`와 유사한 방식으로 특정 항목 속성의 조건을 확인하는 데 사용할 수 있습니다. **Topics** + [구문](#ql-reference.multiplestatements.transactions.syntax) + [파라미터](#ql-reference.multiplestatements.transactions.parameters) + [반환 값](#ql-reference.multiplestatements.transactions.return) + [예제](#ql-reference.multiplestatements.transactions.examples) ## 구문 ``` [ { "Statement":" statement ", "Parameters":[ { " parametertype " : " parametervalue " }, ...] } , ... ] ``` ## 파라미터 *** 명령문*** (필수) DynamoDB용 PartiQL에서 지원되는 문입니다. 전체 트랜잭션은 읽기 또는 쓰기 문으로 구성해야 합니다. 하나의 트랜잭션에서 두 가지를 모두 혼용할 수는 없습니다. ***parametertype*** (선택 사항) ParitPartiQL 문을 지정할 때 파라미터가 사용된 경우 DynamoDB 형식입니다. ***parametervalue*** (선택 사항) PartiQL 문을 지정할 때 파라미터가 사용된 경우 파라미터 값입니다. ## 반환 값 이 문은 쓰기 작업(INSERT, UPDATE 또는 DELETE)에 대한 값을 반환하지 않습니다. 그러나 WHERE 절에 지정된 조건에 따라 읽기 작업 (SELECT) 에 대해 서로 다른 값을 반환합니다. **참고** Singleton INSERT, UPDATE 또는 DELETE 작업 중 하나에서 오류를 반환하는 경우 트랜잭션이 `TransactionCanceledException` 예외로 취소되고 취소 이유 코드에 개별 singleton 작업의 오류가 포함됩니다. ## 예제 다음 예는 여러 문을 트랜잭션으로 실행합니다. ------ #### [ AWS CLI ] 1. 다음 JSON 코드를 partiql.json이라는 파일에 저장합니다. ``` [ { "Statement": "EXISTS(SELECT * FROM \"Music\" where Artist='No One You Know' and SongTitle='Call Me Today' and Awards is MISSING)" }, { "Statement": "INSERT INTO Music value {'Artist':?,'SongTitle':'?'}", "Parameters": [{\"S\": \"Acme Band\"}, {\"S\": \"Best Song\"}] }, { "Statement": "UPDATE \"Music\" SET AwardsWon=1 SET AwardDetail={'Grammys':[2020, 2018]} where Artist='Acme Band' and SongTitle='PartiQL Rocks'" } ] ``` 1. 명령 프롬프트에서 다음 명령을 실행합니다. ``` aws dynamodb execute-transaction --transact-statements file://partiql.json ``` ------ #### [ Java ] ``` public class DynamoDBPartiqlTransaction { public static void main(String[] args) { // Create the DynamoDB Client with the region you want AmazonDynamoDB dynamoDB = createDynamoDbClient("us-west-2"); try { // Create ExecuteTransactionRequest ExecuteTransactionRequest executeTransactionRequest = createExecuteTransactionRequest(); ExecuteTransactionResult executeTransactionResult = dynamoDB.executeTransaction(executeTransactionRequest); System.out.println("ExecuteTransaction successful."); // Handle executeTransactionResult } catch (Exception e) { handleExecuteTransactionErrors(e); } } private static AmazonDynamoDB createDynamoDbClient(String region) { return AmazonDynamoDBClientBuilder.standard().withRegion(region).build(); } private static ExecuteTransactionRequest createExecuteTransactionRequest() { ExecuteTransactionRequest request = new ExecuteTransactionRequest(); // Create statements List statements = getPartiQLTransactionStatements(); request.setTransactStatements(statements); return request; } private static List getPartiQLTransactionStatements() { List statements = new ArrayList(); statements.add(new ParameterizedStatement() .withStatement("EXISTS(SELECT * FROM "Music" where Artist='No One You Know' and SongTitle='Call Me Today' and Awards is MISSING)")); statements.add(new ParameterizedStatement() .withStatement("INSERT INTO "Music" value {'Artist':'?','SongTitle':'?'}") .withParameters(new AttributeValue("Acme Band"),new AttributeValue("Best Song"))); statements.add(new ParameterizedStatement() .withStatement("UPDATE "Music" SET AwardsWon=1 SET AwardDetail={'Grammys':[2020, 2018]} where Artist='Acme Band' and SongTitle='PartiQL Rocks'")); return statements; } // Handles errors during ExecuteTransaction execution. Use recommendations in error messages below to add error handling specific to // your application use-case. private static void handleExecuteTransactionErrors(Exception exception) { try { throw exception; } catch (TransactionCanceledException tce) { System.out.println("Transaction Cancelled, implies a client issue, fix before retrying. Error: " + tce.getErrorMessage()); } catch (TransactionInProgressException tipe) { System.out.println("The transaction with the given request token is already in progress, consider changing " + "retry strategy for this type of error. Error: " + tipe.getErrorMessage()); } catch (IdempotentParameterMismatchException ipme) { System.out.println("Request rejected because it was retried with a different payload but with a request token that was already used, " + "change request token for this payload to be accepted. Error: " + ipme.getErrorMessage()); } catch (Exception e) { handleCommonErrors(e); } } private static void handleCommonErrors(Exception exception) { try { throw exception; } catch (InternalServerErrorException isee) { System.out.println("Internal Server Error, generally safe to retry with exponential back-off. Error: " + isee.getErrorMessage()); } catch (RequestLimitExceededException rlee) { System.out.println("Throughput exceeds the current throughput limit for your account, increase account level throughput before " + "retrying. Error: " + rlee.getErrorMessage()); } catch (ProvisionedThroughputExceededException ptee) { System.out.println("Request rate is too high. If you're using a custom retry strategy make sure to retry with exponential back-off. " + "Otherwise consider reducing frequency of requests or increasing provisioned capacity for your table or secondary index. Error: " + ptee.getErrorMessage()); } catch (ResourceNotFoundException rnfe) { System.out.println("One of the tables was not found, verify table exists before retrying. Error: " + rnfe.getErrorMessage()); } catch (AmazonServiceException ase) { System.out.println("An AmazonServiceException occurred, indicates that the request was correctly transmitted to the DynamoDB " + "service, but for some reason, the service was not able to process it, and returned an error response instead. Investigate and " + "configure retry strategy. Error type: " + ase.getErrorType() + ". Error message: " + ase.getErrorMessage()); } catch (AmazonClientException ace) { System.out.println("An AmazonClientException occurred, indicates that the client was unable to get a response from DynamoDB " + "service, or the client was unable to parse the response from the service. Investigate and configure retry strategy. "+ "Error: " + ace.getMessage()); } catch (Exception e) { System.out.println("An exception occurred, investigate and configure retry strategy. Error: " + e.getMessage()); } } } ``` ------ 다음 예제에서는 DynamoDB가 WHERE 절에 지정된 조건이 다른 항목을 읽을 때 서로 다른 반환 값을 보여줍니다. ------ #### [ AWS CLI ] 1. 다음 JSON 코드를 partiql.json이라는 파일에 저장합니다. ``` [ // Item exists and projected attribute exists { "Statement": "SELECT * FROM "Music" WHERE Artist='No One You Know' and SongTitle='Call Me Today'" }, // Item exists but projected attributes do not exist { "Statement": "SELECT non_existent_projected_attribute FROM "Music" WHERE Artist='No One You Know' and SongTitle='Call Me Today'" }, // Item does not exist { "Statement": "SELECT * FROM "Music" WHERE Artist='No One I Know' and SongTitle='Call You Today'" } ] ``` 1. 명령 프롬프트에서 다음 명령. ``` aws dynamodb execute-transaction --transact-statements file://partiql.json ``` 1. 다음 응답이 반환됩니다. ``` { "Responses": [ // Item exists and projected attribute exists { "Item": { "Artist":{ "S": "No One You Know" }, "SongTitle":{ "S": "Call Me Today" } } }, // Item exists but projected attributes do not exist { "Item": {} }, // Item does not exist {} ] } ``` ------