CODEWITHSUNDEEP
pythonamazon-web-servicesamazon-dynamodbboto3
weka1
weka1

Reputation: 737

How to rename DynamoDB column/key

In one of my DynamoDb tables I have a column/key named "status", which turned out to be a reserved keyword. Unfortunately it isn't an option to delete the whole table and reinitiate it. How can I rename the key?

Here is the Lambda Code that causes the Exception:

try :
            response = table.query(
                IndexName='myId-index',
                KeyConditionExpression=Key('myId').eq(someId)
            )
            for item in response['Items']:
                print('Updating Item: ' + item['id'])
                table.update_item(
                    Key={
                        'id': item['id']
                    },
                    UpdateExpression='SET myFirstKey = :val1, mySecondKey = :val2, myThirdKey = :val3, myFourthKey = :val4, myFifthKey = :val5, status = :val6',
                    ExpressionAttributeValues={
                        ':val1': someValue1,
                        ':val2': someValue2,
                        ':val3': someValue3,
                        ':val4': someValue4,
                        ':val5': someValue5,
                        ':val6': someValue6
                    }
                )
except Exception, e:
            print ('ok error: %s' % e)

And here is the Exception:

2016-06-14 18:47:24 UTC+2 ok error: An error occurred (ValidationException) when calling the UpdateItem operation: Invalid UpdateExpression: Attribute name is a reserved keyword; reserved keyword: status

Upvotes: 12

Views: 28343

Answers (3)

Stephen
Stephen

Reputation: 357

Using the NoSQL Workbench app AWS supports I exported a copy of the table which had the column name(s) I wanted to change. I opened the JSON file NoSQL Workbench created then did a simple Find/Replace for the name of the column in question.

With the names looking correct on the .JSON file I re-imported the table back into dynamodb using the NoSQL app. The import overwrites existing data which will wipe out the bad column name.

If you have a HUGE data set, downloading a copy to your local computer may not be a good solution, but for my small table it worked pretty well.

Upvotes: 1

Thomas Bayer
Thomas Bayer

Reputation: 71

There is a simple solution instead of renaiming a column: Use projection-expression and expression-attribute-names in your query.

I run over the same problem (my table contains the column "name". Here ist a sample query:

TableName: 'xxxxxxxxxx',
  ExpressionAttributeNames: {
    '#A': 'country',
    '#B': 'postcode',
    '#C': 'name'
  },
  ExpressionAttributeValues: {
    ':a': {S: 'DE'},
    ':c': {S: 'Peter Benz'}
  },
  FilterExpression: 'country = :a AND #C = :c',
  ProjectionExpression: '#A, #B, #C'

Upvotes: 5

Shibashis
Shibashis

Reputation: 8401

There is no real easy way to rename a column. You will have to create a new attribute for each of the entries and then delete all the values for the existing attribute.

There is no reason to drop your attribute/column, if you are having trouble querying the table use Expression Attribute Names.

From the Expression Attribute Names documentation:

On some occasions, you might need to write an expression containing an attribute name that conflicts with a DynamoDB reserved word... To work around this, you can define an expression attribute name. An expression attribute name is a placeholder that you use in the expression, as an alternative to the actual attribute name.

Upvotes: 14

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