# DynamoDB UpdateExpression Functionality

**URL:** <https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324>\
**Category:** Feature Requests\
**Tags:** aws-dynamodb\
**Created:** [April 15, 2024, 9:05pm UTC](https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324 "2024-04-15T21:05:39Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![workflowsy](https://dub1.discourse-cdn.com/n8n/user_avatar/community.n8n.io/workflowsy/32/37876_2.png) [@workflowsy](https://community.n8n.io/u/workflowsy)\
**Post date:** [April 15, 2024, 9:05pm UTC](https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324/1 "2024-04-15T21:05:39Z")

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Currently DynamoDB does not offer the functionality natively within n8n to update an existing item and add additional attributes. I think this would be very helpful to use as a datastore if needed.

UpdateExpression would need to be added to allow for items to be updated during an upsert.

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<div class="post-metadata">

**Author:** ![workflowsy](https://dub1.discourse-cdn.com/n8n/user_avatar/community.n8n.io/workflowsy/32/37876_2.png) [@workflowsy](https://community.n8n.io/u/workflowsy)\
**Post date:** [May 11, 2024, 12:16am UTC](https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324/2 "2024-05-11T00:16:51Z")

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I’ve addressed this for the time being with an AWS Lambda (see code below) as well as the sample event that allows me to update the table contents without a complete overwrite. It admittedly feels a little hacky, but hopefully it’s enough of a solution to help others in the foreseeable future.

```auto
import boto3
from boto3.dynamodb.conditions import Key
from botocore.exceptions import ClientError

def lambda_handler(event, context):
    # Extract the table name, key, and updates from the event
    table_name = event['table_name']
    key = event['key']
    updates = event['updates'] # Expecting a list of dictionaries with 'attribute_name', 'value_to_add', and 'value_type'

    # Initialize a DynamoDB client
    dynamodb = boto3.resource('dynamodb')
    table = dynamodb.Table(table_name)

    # Build the update expression and attribute values dynamically
    update_expression_parts = []
    expression_attribute_values = {}
    expression_attribute_names = {}

    for i, update in enumerate(updates):
        attr = update['attribute_name']
        val = update['value_to_add']
        value_type = update.get('value_type', 'numeric') # Assume numeric if value_type is not provided
        placeholder = f"#attr{i}"
        value_placeholder = f":val{i}"

        if value_type == 'numeric':
            update_expression_parts.append(f"{placeholder} = if_not_exists({placeholder}, :zero) + {value_placeholder}")
            expression_attribute_values[':zero'] = 0 # Set the initial value to 0 for numeric attributes
        else:
            update_expression_parts.append(f"{placeholder} = if_not_exists({placeholder}, :empty) + {value_placeholder}")
            expression_attribute_values[':empty'] = '' # Set the initial value to an empty string for string attributes

        expression_attribute_values[value_placeholder] = val
        expression_attribute_names[placeholder] = attr

    final_update_expression = "SET " + ", ".join(update_expression_parts)

    # Update the item in DynamoDB
    try:
        response = table.update_item(
            Key=key,
            UpdateExpression=final_update_expression,
            ExpressionAttributeNames=expression_attribute_names,
            ExpressionAttributeValues=expression_attribute_values,
            ReturnValues='UPDATED_NEW'
        )
        return response
    except ClientError as e:
        print(e.response['Error']['Message'])
        return e.response['Error']['Message']

```

Sample Input Event

````auto
updates = [
    {"attribute_name": "Prompt Tokens", "value_to_add": 427, "value_type": "numeric"},
    {"attribute_name": "Completion Tokens", "value_to_add": 108, "value_type": "numeric"},
    {"attribute_name": "Total Tokens", "value_to_add": 535, "value_type": "numeric"},
    {"attribute_name": "Log", "value_to_add": "New log entry", "value_type": "string"}
]```

If anyone has questions, feel free to reach out!
````

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<div class="post-metadata">

**Author:** ![weilies\_chok](https://dub1.discourse-cdn.com/n8n/user_avatar/community.n8n.io/weilies_chok/32/34428_2.png) [@weilies\_chok](https://community.n8n.io/u/weilies_chok)\
**Post date:** [September 23, 2024, 1:51am UTC](https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324/3 "2024-09-23T01:51:06Z")

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still i think it’s best n8n “DynamoDB official” node should support the proper UPSERT without remove those fields which are not requested. Million thanks!

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**Author:** ![Radu](https://avatars.discourse-cdn.com/v4/letter/r/b2d939/32.png) [@Radu](https://community.n8n.io/u/Radu)\
**Post date:** [October 5, 2024, 11:50am UTC](https://community.n8n.io/t/dynamodb-updateexpression-functionality/44324/4 "2024-10-05T11:50:58Z")

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+1 for upsert