How do I query DynamoDB2 table by global secondary index only using boto 2.25.0?

Question

This is a continuation** of my quest to switch from regular DynamoDB tables to DynamoDB2 ones with Global Secondary Indices.

So I created my table as shown here and then added the following two elements:

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"}'})

What I want to do now is retrieve items by either their (i) unique firstKey values or (ii) unique secondKey values. The 1st one is easy:

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

I can't figure out how to do the 2nd one. This does not work:

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

producing The provided key element does not match the schema. OK that's expected. When I do this:

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

I get You must specify more than one key to filter on.

So how do I get it to work? Note that when I have the value of secondKey of an item, I do NOT know its corresponding firstKey.

===== UPDATE: Here are a couple of other things that I've tried:

This

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

produced

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

In the block below, the query statement did not produce any errors

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

but the print gave me

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

Answer 1

It is possible using LSI/GSI.

See the boto tutorial here (search for LSI, and you will get the example). DynamoDB2 — boto v2.25.0 : http://boto.readthedocs.org/en/latest/ref/dynamodb2.html

Adding a full working example (tried with 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']

The result of execution is:

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

Also adding the exact packages (Due to Dynamo1/2 - there is chance of mistake):

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