AWS CLI DynamoDB command

Question

I am writing a shell script file for doing some operation on dynamoDB using AWS CLI. I am trying to update an attribute in an item in a dynamodb table if the attribute already exists.

However, I am not comfortable with the syntax of the update-item command. I want to update an attribute named 'conf' with some value. However, I am not able to figure out the syntax for SET in thie command. This is what I have got till now :

aws dynamodb update-item --table-name MY_TABLE_NAME --key '{"AccountId": {"S": accountId}}'

I know the above has to followed by the SET option.

Any help would be appreciated.

James · Accepted Answer · 2015-09-27 06:38:10Z

2

I think it would look something like this:

aws dynamodb update-item --table-name MY_TABLE_NAME --key file://update-key.json --update-expression "SET conf = :newconf" --expression-attribute-values file://update-attr-values.json --condition-expression "attribute_exists(conf)" --return-values ALL_NEW

update-key.json

{
    "AccountId": {
        "S": "account123"
    }
}

update-attr-values.json

{
    ":newconf": {
        "S": "new conf value"
    }
}

answered Sep 27, 2015 at 6:38

James

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4 Comments

roger Over a year ago

My usecase if to do this update for various accounts by reading them from a file one at a time. So, I do not want to create separate json files for key and expression attribute values. Can you suggest the command that just updates an attribute value without using any json files ?

James Over a year ago

You could use shell script variables. How are you iterating through the file?

roger Over a year ago

I want a similar command for update-item where I do not need to provide json files. I will iterate through the file line by line and for every line, I will update the table. Hence, I want to inject the value of shell script variables in the command and not use separate json files.

roger Over a year ago

Here is the command to query a table for a given reference id : aws dynamodb query --table-name MY_TABLE --select SPECIFIC_ATTRIBUTES --attributes-to-get "AccountId" --key-conditions '{"ReferenceId": {"AttributeValueList": [ {"S": '\"$referenceId\"' } ], "ComparisonOperator": "EQ"} }' --limit 1 | jq '.Items[0].AccountId.S' I want a similar command to update an attribute of a table without using json files.

Mazzy · Accepted Answer · 2017-08-03 12:56:15Z

2

It is possible to do this without files but the answer is hidden in the 700+ pages developer guide of dynamodb:

aws dynamodb update-item \
--region MY_REGION \
--table-name MY_TABLE_NAME \
--key='{"AccountId": {"S": accountId}}' \
--update-expression 'SET conf=:newconf' \
--expression-attribute-values '{":newconf":{"S":"new conf value"}}'

The developer guide of Dynamo DB can be found here: Dynamo DB Developer guide

On page 206 by Atomic Counters, there is an example of how to use --expression-attribute-values without a file

answered Aug 3, 2017 at 12:56

Mazzy

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