Query DynamoDB with a hash key and a range key with Boto3

Question

I am having trouble using AWS Boto3 to query DynamoDB with a hash key and a range key at the same time using the recommend KeyConditionExpression. I have attached an example query:

import boto3 from boto3 import dynamodb from boto3.session import Session dynamodb_session = Session(aws_access_key_id=AWS_KEY,               aws_secret_access_key=AWS_PASS,               region_name=DYNAMODB_REGION) dynamodb = dynamodb_session.resource('dynamodb') table=dynamodb.Table(TABLE_NAME) request = {     'ExpressionAttributeNames': {         '#n0': 'hash_key',         '#n1': 'range_key'     },     'ExpressionAttributeValues': {         ':v0': {'S': MY_HASH_KEY},         ':v1': {'N': GT_RANGE_KEY}     },     'KeyConditionExpression': '(#n0 = :v0) AND (#n1 > :v1)',     'TableName': TABLE_NAME } response = table.query(**request) 

When I run this against a table with the following scheme:

Table Name: TABLE_NAME Primary Hash Key: hash_key (String) Primary Range Key: range_key (Number) 

I get the following error and I cannot understand why:

ClientError: An error occurred (ValidationException) when calling the Query operation: Invalid KeyConditionExpression: Incorrect operand type for operator or function; operator or function: >, operand type: M 

From my understanding the type M would be a map or dictionary type and I am using a type N which is a number type and matches my table scheme for the range key. If someone could explain why this error is happening or I am also open to a different way of accomplishing the same query even if you cannot explain why this error exists.

Answer 1

The Boto 3 SDK constructs a Condition Expression for you when you use the Key and Attr functions imported from boto3.dynamodb.conditions:

response = table.query(     KeyConditionExpression=Key('hash_key').eq(hash_value) & Key('range_key').eq(range_key_value)  ) 

Reference: Step 4: Query and Scan the Data

Hope it helps

Answer 2

Adding this solution as the accepted answer did not address why the query used did not work.

TLDR: Using query on a Table resource in boto3 has subtle differences as opposed to using client.query(...) and requires a different syntax.

The syntax is valid for a query on a client, but not on a Table. The ExpressionAttributeValues on a table do not require you to specify the data type. Also if you are executing a query on a Table resource you do not have to specify the TableName again.

Working solution:

from boto3.session import Session  dynamodb_session = Session(aws_access_key_id=AWS_KEY,aws_secret_access_key=AWS_PASS,region_name=DYNAMODB_REGION)  dynamodb = dynamodb_session.resource('dynamodb') table = dynamodb.Table(TABLE_NAME)  request = {     'ExpressionAttributeNames': {         '#n0': 'hash_key',         '#n1': 'range_key'     },     'ExpressionAttributeValues': {         ':v0': MY_HASH_KEY,         ':v1': GT_RANGE_KEY     },     'KeyConditionExpression': '(#n0 = :v0) AND (#n1 > :v1)', } response = table.query(**request) 

I am the author of a package called botoful which might be useful to avoid dealing with these complexities. The code using botoful will be as follows:

import boto3 from botoful import Query  client = boto3.Session(     aws_access_key_id=AWS_KEY,     aws_secret_access_key=AWS_PASS,     region_name=DYNAMODB_REGION ).client('dynamodb')  results = (     Query(TABLE_NAME)         .key(hash_key=MY_HASH_KEY, range_key__gt=GT_RANGE_KEY)         .execute(client) )  print(results.items)