amazon-dynamodb - 使用值列表查询 DynamoDB GSI

Question

我有一个“团队成员”表，主分区键为“team_id”，主排序键为“email”，GSI 的分区键为“email”。

给定一个电子邮件列表，我想以最有效的方式找到列表中所有电子邮件的所有成员资格。

我知道对于一封电子邮件，我可以执行以下操作:

 Membership membership = new Membership();
 membership.setEmail(email.toLowerCase());

 DynamoDBQueryExpression<Membership> expression = new DynamoDBQueryExpression<Membership>()
                .withHashKeyValues(membership)
                .withIndexName(EMAIL_INDEX)
                .withConsistentRead(false);

 return mapper.query(Membership.class, expression);

它返回给定电子邮件的成员资格列表。

(因此对于我的电子邮件列表，我可以对列表中的每一封电子邮件执行上述操作，但我想知道是否可以一步完成)。

我希望能够执行以下操作:

List<Membership> memberships = allEmails.stream().map(email -> {
            Membership m = new Membership();
            m.setEmail(email.toLowerCase());
            return m;
        }).collect(Collectors.toList());

        DynamoDBQueryExpression<Membership> expression = new DynamoDBQueryExpression<Membership>()
                .withHashKeyValues(memberships) // <--- passing a list
                .withIndexName(EMAIL_INDEX)
                .withConsistentRead(false);

这显然不起作用。

有哪些替代方案？

Answer 1

Batch get item api 可用于从主表中获取多个分区键。但是，它不能用于从 GSI 获取多个项目。

我很欣赏这个答案可能无法解决您的问题。简而言之，没有其他替代解决方案。

Batch get item java

try {

            TableKeysAndAttributes forumTableKeysAndAttributes = new TableKeysAndAttributes(forumTableName);
            // Add a partition key
            forumTableKeysAndAttributes.addHashOnlyPrimaryKeys("Name", "Amazon S3", "Amazon DynamoDB");

            TableKeysAndAttributes threadTableKeysAndAttributes = new TableKeysAndAttributes(threadTableName);
            // Add a partition key and a sort key
            threadTableKeysAndAttributes.addHashAndRangePrimaryKeys("ForumName", "Subject", "Amazon DynamoDB",
                "DynamoDB Thread 1", "Amazon DynamoDB", "DynamoDB Thread 2", "Amazon S3", "S3 Thread 1");

            System.out.println("Making the request.");

            BatchGetItemOutcome outcome = dynamoDB.batchGetItem(forumTableKeysAndAttributes,
                threadTableKeysAndAttributes);

            Map<String, KeysAndAttributes> unprocessed = null;

            do {
                for (String tableName : outcome.getTableItems().keySet()) {
                    System.out.println("Items in table " + tableName);
                    List<Item> items = outcome.getTableItems().get(tableName);
                    for (Item item : items) {
                        System.out.println(item.toJSONPretty());
                    }
                }

                // Check for unprocessed keys which could happen if you exceed
                // provisioned
                // throughput or reach the limit on response size.
                unprocessed = outcome.getUnprocessedKeys();

                if (unprocessed.isEmpty()) {
                    System.out.println("No unprocessed keys found");
                }
                else {
                    System.out.println("Retrieving the unprocessed keys");
                    outcome = dynamoDB.batchGetItemUnprocessed(unprocessed);
                }

            } while (!unprocessed.isEmpty());

        }
        catch (Exception e) {
            System.err.println("Failed to retrieve items.");
            System.err.println(e.getMessage());
        }