Melakukan transaksi dengan PartiQL untuk DynamoDB

Bagian ini menjelaskan cara menggunakan transaksi dengan PartiQL untuk DynamoDB. Transaksi PartiQL dibatasi hingga 100 total pernyataan (tindakan).

Untuk informasi lebih lanjut tentang transaksi DynamoDB, lihat Mengelola alur kerja kompleks dengan transaksi DynamoDB.

catatan

Seluruh transaksi harus terdiri dari pernyataan baca atau pernyataan tulis. Anda tidak dapat menggabungkan keduanya dalam satu transaksi. Fungsi EXISTS merupakan pengecualian. Anda dapat menggunakannya untuk memeriksa kondisi atribut tertentu dari item dengan cara yang mirip ConditionCheck dengan operasi TransactWriteItemsAPI.

Sintaks

[
   {
      "Statement":" statement ",
      "Parameters":[
         {
            " parametertype " : " parametervalue "
         }, ...]
   } , ...
]

Parameter

statement

(Diperlukan) Pernyataan yang didukung PartiQL untuk DynamoDB.

catatan

Seluruh transaksi harus terdiri dari pernyataan baca atau pernyataan tulis. Anda tidak dapat menggabungkan keduanya dalam satu transaksi.

parametertype

(Opsional) Jenis DynamoDB, jika parameter digunakan saat menentukan pernyataan PartiQL.

parametervalue

(Opsional) Nilai parameter jika parameter digunakan saat menentukan pernyataan PartiQL.

Nilai yang dikembalikan

Pernyataan ini tidak mengembalikan nilai apa pun untuk operasi Tulis (INSERT, UPDATE, atau DELETE). Namun, ia mengembalikan nilai yang berbeda untuk operasi Baca (SELECT) berdasarkan kondisi yang ditentukan dalam klausul WHERE.

catatan

Jika salah satu operasi INSERT, UPDATE, atau DELETE singleton mengembalikan kesalahan, transaksi dibatalkan dengan pengecualian TransactionCanceledException, dan kode alasan pembatalan termasuk kesalahan dari operasi singleton individual.

Contoh

Contoh berikut menjalankan beberapa pernyataan sebagai sebuah transaksi.

AWS CLI

1. Simpan kode JSON berikut ke file bernama partiql.json.

   [
       {
           "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'"
       }
   ]

2. Jalankan perintah berikut di prompt perintah.

   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<ParameterizedStatement> statements = getPartiQLTransactionStatements();

        request.setTransactStatements(statements);
        return request;
    }

    private static List<ParameterizedStatement> getPartiQLTransactionStatements() {
        List<ParameterizedStatement> statements = new ArrayList<ParameterizedStatement>();

        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());
        }
    }

}

Contoh berikut menunjukkan nilai pengembalian yang berbeda ketika DynamoDB membaca item dengan kondisi berbeda yang ditentukan dalam klausul WHERE.

AWS CLI

1. Simpan kode JSON berikut ke file bernama partiql.json.

   [
       // 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'"
       }
   ]

2. perintah berikut di prompt perintah.

   aws dynamodb execute-transaction --transact-statements  file://partiql.json

3. Respons berikut dikembalikan:

   {
       "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
           {}
       ]
   }