Scan

Parameters

• When you use the --limit parameter with the scan operation in DynamoDB and set it to 5, it indeed instructs DynamoDB to evaluate only the first 5 items in the table.

  • Without --filter: If you set --limit 5 without a filter, DynamoDB evaluates the first 5 items and returns them as the result of the scan.

  • With --filter: If you set --limit 5 and also specify a --filter expression, DynamoDB still evaluates the first 5 items. However, it only returns those that match the filter criteria. If fewer than 5 items match the filter, then fewer than 5 items are returned. If none of the first 5 items match the filter, it returns no items. In either case, it only evaluates 5 items before stopping.

If you do not use a filter expression, ScannedCount and Count have the same value.

• The page-size parameter will determine the number of items returned in each page of a query.

• If there are more items available than the specified --max-items value, the response includes a NextToken value.

Best practices

Avoid using scan operation on large table or index, use Filter --filter-expression and Projection --projection-expression , and --page-size to get specific data instead.

Trivia

• 1 single DynamoDB scan can retrieve max 1MB.