CODEWITHSUNDEEP
amazon-dynamodb
Adi GuN
Adi GuN

Reputation: 1294

Query using just secondary indexes in dynamo DB

Can I query in dynamodb tables using conditions just on secondary index. I don't want to keep any condition on the hashkey. Is there a way to do it?

Upvotes: 1

Views: 4583

Answers (6)

SURAJ MANIYAR
SURAJ MANIYAR

Reputation: 79

Yes you can query DynamoDb with just secondary indexes without any use of HASH key.. Let's say you have DynamoDB table EmployeeData with columns EmployeeID,Department and created_at_date..The partition key for this table is EmployeeID and sort key is Department.. You want to fetch data based on date created ..So first create secondary index with name date-index on your DynamoDB table.. Then you can fetch data with secondary index using below code:

from boto3.dynamodb.conditions import Key
dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('EmployeeData')
response = table.query(IndexName="date-index",
    KeyConditionExpression=Key('created_at_date').eq('2020-01-03'))
print(response)

Upvotes: 0

Adarsh
Adarsh

Reputation: 3583

TL;DR Yes it is possible to query based on secondary indexes.

Example:

So consider a table with the following structure:

- user_id (partition key)
- created_at (sort key)
- account_id
- api_path
- execution_time
- platform
- ttl
- metadata

If you want to query based on account_id, you can create a GSI as follows:

account_id (partition key)
created_at (sort key)

lets say you called this index: account_id-created_at-index

Now its possible to query them as follows (python taken as language of choice for brevity, this applies to all their SDKs):

import boto3
from boto3.dynamodb.conditions import Key

dynamodb = boto3.resource('dynamodb')
table = db.Table('table_name')
response = table.query(KeyConditionExpression=Key('account_id').eq(some_account_id), IndexName=account_id-created_at-index)

Note the IndexName param here which is key.

If there are any items that apply to the KeyConditionExpression, they are accessible in the response['Items'] as list of objects.

Upvotes: 0

Rohit K Choudhary
Rohit K Choudhary

Reputation: 79

You can query the dynamodb with secondry indexes.

let params = {
       TableName: 'users',
        KeyConditionExpression: "#_id = :_id",
        IndexName: "_id-index",
        ExpressionAttributeNames:{
            "#_id": "_id"
        },
        ExpressionAttributeValues: {
            ":_id":userId
        }
    };
    documentClient.query(params, function (err, data) {
        if (err) {
            callback(err);
        }
        else {
            if (data && data.Items && data.Items[0].accessToken) {
                userData = data.Items[0];
            }
            else userData ={};

            callback(null,{userData:userData})
        }
    })

Upvotes: 0

mkobit
mkobit

Reputation: 47319

The Query operation always requires the hash key, even if you are querying an LSI or a GSI.

Upvotes: 0

Chet
Chet

Reputation: 22105

As of December 2013, you can. Dynamo supports Global Secondary Indexes.

See the documentation page for how to perform queries. You basically have to specify the table and index. You can either get back a record if you projected all the attributes on the index, or else you get the original hash key which you can use to look up the object in the table like you might have previously.

Upvotes: 1

prestomation
prestomation

Reputation: 7450

No, to query DynamoDB you MUST know the hash key. If you don't know the hash key the only way to get data out is a full table Scan.

Upvotes: 0

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