boto - 在 AWS DynamoDb 上查询 Range 键的最大值

Question

DynamoDB 相当于什么

SELECT MAX(RANGE_KEY) FROM MYTABLE WHERE PRIMARYKEY = "value"

我能想到的最好的是

from boto.dynamodb2.table import Table as awsTable

tb = awsTable("MYTABLE")
rs = list(tb.query_2(PRIMARYKEY__eq="value", reverse=True, limit=1))
MAXVALUE = rs[0][RANGE_KEY]

有一个更好的方法吗？

Answer 1

这是正确的方法。

因为 Hash Key 匹配的记录是按 Range Key 排序的，所以按降序获取第一个将为您提供具有最大范围键的记录。

Query results are always sorted by the range key. If the data type of the range key is Number, the results are returned in numeric order; otherwise, the results are returned in order of ASCII character code values. By default, the sort order is ascending. To reverse the order use the ScanIndexForward parameter set to false.

查询和扫描操作 - Amazon DynamoDB: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html

注意:设置 reverse通过 boto API 设置为 true 的参数等效于设置 ScanIndexForward通过 native AWS API 设置为 false。