Databricks Certified Data Engineer Professional Exam - Topic 1 Question 19 Discussion

Actual exam question for Databricks's Databricks Certified Data Engineer Professional exam

Question #: 19
Topic #: 1

[All Databricks Certified Data Engineer Professional Questions]

The downstream consumers of a Delta Lake table have been complaining about data quality issues impacting performance in their applications. Specifically, they have complained that invalid latitude and longitude values in the activity_details table have been breaking their ability to use other geolocation processes.

A junior engineer has written the following code to add CHECK constraints to the Delta Lake table:

A senior engineer has confirmed the above logic is correct and the valid ranges for latitude and longitude are provided, but the code fails when executed.

Which statement explains the cause of this failure?

ABecause another team uses this table to support a frequently running application, two-phase locking is preventing the operation from committing.

BThe activity details table already exists; CHECK constraints can only be added during initial table creation.

CThe activity details table already contains records that violate the constraints; all existing data must pass CHECK constraints in order to add them to an existing table.

DThe activity details table already contains records; CHECK constraints can only be added prior to inserting values into a table.

EThe current table schema does not contain the field valid coordinates; schema evolution will need to be enabled before altering the table to add a constraint.

Show Suggested Answer

Suggested Answer: B

A unit test is designed to verify the correctness of a small, isolated piece of code, typically a single function. Testing a mathematical function that calculates the area under a curve is an example of a unit test because it is testing a specific, individual function to ensure it operates as expected.

Software Testing Fundamentals: Unit Testing

by Ilene at Sep 12, 2024, 01:20 PM

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Rodolfo

3 months ago

Option B sounds plausible too, but I lean towards C.

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Kattie

3 months ago

Yeah, I agree with C. Those invalid records are probably causing the issue.

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Delsie

3 months ago

Wait, are you sure about that? I thought you could add constraints anytime.

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Pearlie

4 months ago

I think it's option C. Existing data must comply with the new constraints.

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Pearline

4 months ago

CHECK constraints can't be added to existing tables, right?

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Tayna

4 months ago

I think the problem might be that the existing records in the table don’t meet the new constraints, which would prevent them from being added.

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Aleisha

4 months ago

I feel like the constraints can only be added when creating the table, but I’m not completely confident about that.

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Galen

4 months ago

This seems similar to a practice question where we had to deal with existing data violating constraints. I think that might be the issue here.

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Christiane

5 months ago

I remember we discussed CHECK constraints in class, but I’m not sure if they can be added after the table is created.

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Ashlyn

5 months ago

Ah I see, option E mentions the need for schema evolution. That could be the key here. If the table doesn't have the right field structure, we'd need to update the schema before adding the constraint. I'll mark that as my best guess.

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Roslyn

5 months ago

I'm a bit confused here. The senior engineer confirmed the logic is correct, so I don't think it's an issue with the constraint itself. Maybe there's something about the Delta Lake table structure or schema that's preventing the change from going through.

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Son

5 months ago

Hmm, this seems tricky. I'll need to carefully read through the question and options to understand the constraints around adding CHECK constraints to an existing Delta Lake table.

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Merissa

5 months ago

Okay, let me think this through. The question mentions that the table already exists, so that rules out options A and D which talk about creating a new table. I'm leaning towards C since it mentions the table already containing records that may violate the constraints.

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Emile

5 months ago

Ah, I see what they're getting at now. The key is that the question is focusing on settings that can provide effective behavioral healthcare services, but don't necessarily require round-the-clock nursing care. I think answer choice D, psychiatric units in general hospitals or hospital observation units, is probably the best fit based on that.

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Alita

5 months ago

Okay, I've got this. For a VOIP app, I'd want to use a network load balancer to handle the UDP traffic efficiently and minimize latency. The HTTP(S) option doesn't seem right for this use case.

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Dean

10 months ago

Well, at least the senior engineer caught it before it went to production and caused a massive outage. Gotta love those 'I told you so' moments. C is the way to go.

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Yvette

8 months ago

Definitely, it's better to catch these issues early on.

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Jenise

9 months ago

Definitely, it's better to catch these issues early on.

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Blair

9 months ago

Yeah, it's important to validate existing data before adding constraints.

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Aleta

9 months ago

C) The activity details table already contains records that violate the constraints; all existing data must pass CHECK constraints in order to add them to an existing table.

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Marguerita

10 months ago

Yeah, it's important to validate existing data before adding constraints.

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Aileen

10 months ago

C) The activity details table already contains records that violate the constraints; all existing data must pass CHECK constraints in order to add them to an existing table.

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Jerrod

10 months ago

Haha, I bet the junior engineer is feeling pretty embarrassed right now. Should have known better than to try and sneak that in without checking the existing data! C is the right choice.

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Elza

10 months ago

I agree, C is the correct answer. It's important to make sure existing data meets the constraints before adding them, otherwise the operation will fail. Learned that the hard way on a previous project.

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Felicidad

9 months ago

Lesson learned: always check existing data before applying constraints.

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Sharmaine

9 months ago

Definitely, it can save a lot of time and prevent failures in the long run.

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Mitsue

9 months ago

I've encountered a similar issue before. It's crucial to validate existing data before adding constraints.

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Ettie

9 months ago

C) The activity details table already contains records that violate the constraints; all existing data must pass CHECK constraints in order to add them to an existing table.

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Sharika

10 months ago

The answer is C. The table already contains records, so the CHECK constraints can't be added without validating the existing data first. Seems like a common gotcha for Delta Lake tables.

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