如何仅使用boto 2.25.0通过全局二级索引查询DynamoDB2表？

Question

这是我从常规DynamoDB表切换到具有全局二级索引的DynamoDB2表的过程的延续.

所以,我创建了如我的表在这里,然后添加了以下两个因素:

table.put_item(data={'firstKey': 'key01', 'message': '{"firstKey":"key01", "comments": "mess 1 w/o secondKey"}'})
table.put_item(data={'firstKey': 'key02', 'secondKey':'skey01', 'message': '{"firstKey":"key02", "parentId":"skey01", "comments": "mess 2 w/ secondKey"}'})

我现在要做的是通过(i)唯一firstKey值或(ii)唯一secondKey值来检索项目.第一个很简单:

res1 = table.get_item(firstKey='key01')
res1['message']

我无法弄清楚如何做第二个.这不起作用:

res2 = table.get_item(secondKey='skey01')

生产The provided key element does not match the schema.好的,这是预期的.当我这样做:

res2 = table.query(secondKey='skey01',index='secondKeyIndex')

我得到You must specify more than one key to filter on.

那么我该如何让它发挥作用呢？请注意,当我有secondKey一个项目的值时,我不知道它的对应firstKey.

=====更新:以下是我尝试过的其他一些事情:

这个

res2 = table.query(secondKey__eq='skey01',index='secondKeyIndex')

生成

boto.dynamodb2.exceptions.QueryError: You must specify more than one key to filter on.

在下面的块中,该query语句没有产生任何错误

res2 = table.query(secondKey='skey01',secondKey__eq='skey01',index='secondKeyIndex')
for r in res2:
    print res2['secondKey']

但是print给了我

boto.dynamodb2.exceptions.UnknownFilterTypeError: Operator 'secondKey' from 'secondKey' is not recognized.

Answer 1

可以使用LSI/GSI.

请参阅此处的boto教程(搜索LSI,您将获得示例).DynamoDB2 - boto v2.25.0:http://boto.readthedocs.org/en/latest/ref/dynamodb2.html

添加一个完整的工作示例(尝试使用dynamo local:http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Tools.DynamoDBLocal.html)

conn = DynamoDBConnection(
    host='localhost',
    port=8000,
    aws_access_key_id='DEVDB', #anything will do
    aws_secret_access_key='DEVDB', #anything will do
    is_secure=False)
tables = conn.list_tables()
print "Before Creation:", tables

table_name = 'myTable'
if table_name not in tables['TableNames']:
    Table.create(table_name
        , schema=[HashKey('firstKey')]
        , throughput={'read': 5, 'write': 2}
        , global_indexes=[
            GlobalAllIndex('secondKeyIndex', parts=[HashKey('secondKey')], throughput={'read': 5, 'write': 3})]
        , connection=conn
    )
    #print_table_details(conn, table_name)
table = Table(table_name, connection=conn)
item = Item(table, data={
    'firstKey': str(uuid.uuid4()),
    'secondKey': 'DUMMY-second'
})
item.save()
results = table.query(secondKey__eq='DUMMY-second', index='secondKeyIndex')
for res in results:
    print res['firstKey'], res['secondKey']

执行结果是:

91d4d056-1da3-42c6-801e-5b8e9c42a93f DUMMY-second
15c17b09-4975-419a-b603-427e4c765f03 DUMMY-second
dd947b7d-935e-458f-84d3-ed6cd4f32f5a DUMMY-second

还添加了确切的包(由于Dynamo1/2 - 有可能出错):

from boto.dynamodb2.fields import HashKey, RangeKey, GlobalAllIndex
from boto.dynamodb2.layer1 import DynamoDBConnection
from boto.dynamodb2.table import Table
from boto.dynamodb2.items import Item