Question

我想用布尔或SQL之类的条件查询dynamodb表例如Get me all the items where attribute1 = "no" or attribute2="no"

我尝试使用scanRequest.withScanFilter，但所有条件都是通过布尔运算执行的。我该怎么做布尔ORing。？

Answer 1

您可以将ScanRequest的ConditionalOperator设置为＆＃34; OR＆＃34;。默认值为＆＃34; AND＆＃34;

http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Scan.html

ScanRequest scanRequest = new ScanRequest("tableName");
scanRequest.setConditionalOperator(ConditionalOperator.OR);

Map<String, Condition> scanFilter = new HashMap<String, Condition>();
scanFilter.put("attribute1", new Condition().withAttributeValueList(new AttributeValue("no")).withComparisonOperator(ComparisonOperator.EQ));
scanFilter.put("attribute2", new Condition().withAttributeValueList(new AttributeValue("no")).withComparisonOperator(ComparisonOperator.EQ));

scanRequest.setScanFilter(scanFilter);
ScanResult scanResult = dynamo.scan(scanRequest);

for(Map<String, AttributeValue> item : scanResult.getItems()) {
    System.out.println(item);
}

Answer 2

如果您碰巧知道HashKey值，则另一个选项是使用QUERY和FilterExpression。以下是Java SDK的一个示例：

Table table = dynamoDB.getTable(tableName);

Map<String, Object> expressionAttributeValues = new HashMap<String, Object>();
expressionAttributeValues.put(":x", "no");
expressionAttributeValues.put(":y", "no");

QuerySpec spec = new QuerySpec()
    .withHashKey("HashKeyAttributeName", "HashKeyValueHere")
    .withFilterExpression("attribute1 = :x  or attribute2 = :y")
    .withValueMap(expressionAttributeValues);


ItemCollection<QueryOutcome> items = table.query(spec);

Iterator<Item> iterator = items.iterator();

while (iterator.hasNext()) {
    System.out.println(iterator.next().toJSONPretty());
}

有关详细信息，请参阅Specifying Conditions with Condition Expressions。

Answer 3

您还可以在FilterExpression中使用方括号：

const params = { TableName: process.env.PROJECTS_TABLE, IndexName: 'teamId-createdAt-index', KeyConditionExpression: 'teamId = :teamId', ExpressionAttributeValues: { ':teamId': verifiedJwt.teamId, ':userId': verifiedJwt.userId, ':provider': verifiedJwt.provider }, FilterExpression: 'attribute_exists(isNotDeleted) and ((attribute_not_exists(isPrivate)) or (attribute_exists(isPrivate) and userId = :userId and provider = :provider))' };

编写dynamoDB＆＃34; OR＆＃34;条件查询？

3 个答案: