How to fetch and update DynamoDB table items by PartiQL in aws?

Question

I have created a new column to an existing dynamo db table in aws. Now I want a one-time script to populate values to the newly created column for all existing records. I have tried with the cursor as shown below from the PartiQL editor in aws

DECLARE cursor CURSOR FOR SELECT CRMCustomerGuid FROM "Customer";

OPEN cursor;

WHILE NEXT cursor DO
  UPDATE "Customer"
  SET "TimeToLive" = 1671860761
  WHERE "CustomerGuid" = cursor.CRMCustomerGuid;
END WHILE

CLOSE cursor;

But I am getting the error message saying that ValidationException: Statement wasn't well formed, can't be processed: unexpected keyword

Any help is appreciated

Answer 1

DynamoDB is not a relational database and PartiQL is not a full SQL implementation.

Here’s the docs on the language. Cursor isn’t in there.

https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ql-reference.html

My own advice would be to use the plain non-SQL interface first - because with it the calls you can make map directly to the things the database can do.

Once you understand that you may, in some contexts, leverage the PartiQL ability.

Answer 2

From @hunterhacker's comment we know that cursors are not possible with PartiQL. Similarly, we are unable to run multiple types of executions in PartiQL's web editor thus we are unable to do a SELECT then UPDATE.

However, this is quite easily achieved using the CLI or SDK. Below is a simple bash script which will update all of the items in your table with a TTL value, execute from any linux/unix based shell:

for pk in `aws dynamodb scan --table-name Customer --projection-expression 'CustomerGuid' --query 'Items[*].pk.S' --output text`; do
    aws dynamodb update-item \
    --table-name Customer \
    --key '{"CustomerGuid": {"S": "'$pk'"}}' \
    --update-expression "SET #ttl = :ttl" \
    --expression-attribute-names '{"#ttl":"TimeToLive"}' \
    --expression-attribute-values '{":ttl":{"N": "1671860762"}}'
done