Error: dynamodb property projection cannot be empty
Answered by Rafal Wilinski
What's Causing This Error
This error message indicates that the ProjectionExpression
property of the 'Scan' or 'Query' operation is empty or not set. The ProjectionExpression
is used to specify the attributes that need to be returned from an item.
If you have provided the ProjectionExpression
parameter and have given an empty string, you will run into this error.
Solution: Here's How To Resolve It
To solve this error, provide a value for the ProjectionExpression
property. Generally, you can define the name of the attributes you wish to project in the operation.
Here is an example of how to perform a scan operation with a valid 'ProjectionExpression':
import boto3 # Instantiate a client dynamodb = boto3.client('dynamodb', region_name='us-west-2') # Define the parameters table_name = "my_table" projection_expression = "attribute1, attribute2" # Perform the operation response = dynamodb.scan(TableName=table_name, ProjectionExpression=projection_expression) print(response)
You can also use ExpressionAttributeNames
to provide an alias for your attribute names.
import boto3 # Instantiate a client dynamodb = boto3.client('dynamodb', region_name='us-west-2') # Define the parameters table_name = "my_table" projection_expression = "#a1, #a2" expression_attribute_names = {"#a1": "attribute1", "#a2": "attribute2"} # Perform the operation response = dynamodb.scan(TableName=table_name, ProjectionExpression=projection_expression, ExpressionAttributeNames=expression_attribute_names) print(response)
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