CODEWITHSUNDEEP
amazon-dynamodb
Rajesh Kumar
Rajesh Kumar

Reputation: 51

Does AWS Dynamodb limit option in query limits the capacity unit used?

I have a question... If I have 1000 item having same partition key in a table... And if I made a query for this partition key with limit 10 then I want to know does it take read capacity unit for 1000 items or for just 10 items Please clear my doubt

Upvotes: 4

Views: 1377

Answers (3)

Sekki
Sekki

Reputation: 129

According to the aws documentation:

The maximum number of items to evaluate (not necessarily the number of matching items). If DynamoDB processes the number of items up to the limit while processing the results, it stops the operation and returns the matching values up to that point, and a key in LastEvaluatedKey to apply in a subsequent operation, so that you can pick up where you left off.

It seems to me that it means that it will not consume the capacity units for all the items with the same partition key. According to your example the consumed capacity units will be for your 10 items. However since I did not test it I cannot be sure, but that is how I understand the documentation.

Upvotes: 0

Mike Dinescu
Mike Dinescu

Reputation: 55720

The limit option will limit the number of results returned. The capacity consumed depends on the size of the items, and how many of them are accessed (I say accessed because if you have filters in place, more capacity may be consumed than the number of items actually returned would consume if there are items that get filtered out) to produce the results returned.

The reason I mention this is because, for queries, each 4KB of returned capacity is equivalent to 1 read capacity unit.

Why is this important? Because if your items are small, then for each capacity unit consumed you could return multiple items.

For example, if each item is 200 bytes in size, you could be returning up to 20 items for each capacity unit.

Upvotes: 0

Ashan
Ashan

Reputation: 19738

I couldn't find the exact point in the DynamoDB documentation. From my experience it uses only the returned limit for consumed capacity which is 10 (Not 1000).

You can quickly evaluate this also using the following approach.

However, you can specify the ReturnConsumedCapacity parameter in a Query request to obtain this information.

Upvotes: 2

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