Steps for implementation to this project:

• Copy the and paste the code in your AWS Cloud9 command prompt.

1. Create a DynamoDB table

aws dynamodb create-table \

    --table-name Movies \

    --attribute-definitions \

        AttributeName=Title,AttributeType=S \

        AttributeName=Review,AttributeType=S \

    --key-schema \

        AttributeName=Title,KeyType=HASH \

        AttributeName=Review,KeyType=RANGE \

    --provisioned-throughput \

        ReadCapacityUnits=10,WriteCapacityUnits=5

aws dynamodb wait table-exists --table-name Movies

3. Scan the table to get a subset of the attributes

• Scan scanned all 3 items (ScannedCount) in the table -
  "ScannedCount": 3




• But the Filter Expression reduced our result set size down to 2 items (Count) - "Count": 2




• Hence, you should see 2 items in the result set, as the non-key attribute PostedBy references 2 items in Movies table.




• --item '{
  
  "PostedBy": {"S": "User A"}




• Refer the Movies table to check
  

aws dynamodb scan \

    --table-name Movies \

    --filter-expression 'PostedBy = :user' \

    --expression-attribute-values '{

        ":user" : {"S": "User A"}

    }' \

    --return-consumed-capacity TOTAL

4. Scan the table to limit the items number to 1 using --max-items parameter.

aws dynamodb scan \

    --table-name Movies \

    --filter-expression 'PostedBy = :user' \

    --expression-attribute-values '{

        ":user" : {"S": "User A"}

    }' \

    --max-items 1 \

    --return-consumed-capacity TOTAL

• the scan response will show a NextToken which we can then issue to a next scan call to pick up the 2nd item.

NextToken

"NextToken": "eyJFeGNsdXNpdmVTdGFydEtleSI6IG51bGwsICJib3RvX3RydW5jYXRlX2Ftb3VudCI6IDF9"

6. Dealing with Reserved words

• In the Filter Expression, if the attribute name is actually a DynamoDB Reserved Word, it will throw an error - An error occurred (ValidationException) when calling the Scan operation: Invalid FilterExpression: Attribute name is a reserved keyword; reserved keyword: Number




• Because the Number attribute name is actually a DynamoDB Reserved Word.




• This can be solved by putting a placeholder which is a # (pound sign) in the FilterExpression and provide the actual attribute name in the --expression-attribute-names
  

aws dynamodb scan \

    --table-name <Table Name> \

    --filter-expression 'Pictures >= :pictures AND #Number >= :comment' \

    --expression-attribute-values '{

        ":pictures" : {"N": "1"},

        ":Number" : {"S": "Nice"}

    }' \

    --expression-attribute-names '{"#Number" : "number"}' \

    --return-consumed-capacity TOTAL

Cleanup

• Delete the table Movies
  

What we have done so far

We have successfully demonstrated Data Pane operations on DynamoDB scan, using these criteria - Filter Expression, with options, such as max items, --starting-token, Count and ScannedCount, Reserved words.