Exam DP-420 topic 5 question 16 discussion

Actual exam question from Microsoft's DP-420

Question #: 16
Topic #: 5

HOTSPOT -
You have an Azure Cosmos DB Core (SQL) API account named account1.
In account1, you run the following query in a container that contains 100GB of data.

You view the following metrics while performing the query.

For each of the following statements, select Yes if the statement is true. Otherwise, select No.
NOTE: Each correct selection is worth one point.
Hot Area:

Show Suggested Answer

Suggested Answer:

Box 1: No -
Each physical partition should have its own index, but since no index is used, the query is not cross-partition.

Box 2: No -
Index utilization is 0% and Index Look up time is also zero.

Box 3: Yes -
A partition key index will be created, and the query will perform across the partitions.
Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/sql/how-to-query-container

by TRUESON at May 3, 2023, 8:12 a.m.

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WimTS

3 months, 2 weeks ago

YNN When you apply the LOWER() function to c.categoryid, the query engine cannot determine the exact value of the partition key without evaluating the function. As a result, Cosmos DB cannot route the query to a specific partition and must perform a cross-partition query, which can be less efficient.

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matejka

4 months, 1 week ago

I would say YNY

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bcd_6

1 year, 2 months ago

how do we know if it's cross partition query or not?

upvoted 1 times

8fe085a

8 months ago

The third question ask waht happens when the container is recreated with the customerid as partition key, so it is not currently the partition key, therfore the query is cross partition.

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EvanG

1 year, 7 months ago

using a function like Lower on the left side of equality won't use the index in relational dbs. Not sure about Cosmosdb

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TRUESON

1 year, 9 months ago

To correctly answer the question one would have to know the partionkey https://learn.microsoft.com/en-us/azure/cosmos-db/nosql/how-to-query-container

upvoted 1 times

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