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Google Professional Data Engineer Exam - Topic 4 Question 64 Discussion

Actual exam question for Google's Professional Data Engineer exam
Question #: 64
Topic #: 4
[All Professional Data Engineer Questions]

You are using Google BigQuery as your data warehouse. Your users report that the following simple query is running very slowly, no matter when they run the query:

SELECT country, state, city FROM [myproject:mydataset.mytable] GROUP BY country

You check the query plan for the query and see the following output in the Read section of Stage:1:

What is the most likely cause of the delay for this query?

Show Suggested Answer Hide Answer
Suggested Answer: C

by Dalene at Jan 09, 2023, 01:26 PM

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Lai
4 months ago
Concurrent queries might be a factor too, though.
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Dominga
4 months ago
Wait, how can there be so many NULLs? That seems odd.
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Kathrine
4 months ago
I disagree, it could be the NULL values in state or city.
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Izetta
4 months ago
Definitely too many partitions in that table!
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Kristine
4 months ago
I think it's data skew from the country column.
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Janey
5 months ago
I think the issue might be related to concurrent queries. If too many users are running queries at once, it could definitely slow things down.
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Rolande
5 months ago
I feel like NULL values in the state or city columns could be a factor, but I can't recall if they would impact performance this much.
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Mitsue
5 months ago
I'm not entirely sure, but I think having too many partitions can slow down queries too. We practiced a question about that last week.
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Shad
5 months ago
I remember we discussed how data skew can really affect query performance, especially if most rows have the same value in a column.
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Helaine
5 months ago
Hmm, I'm a bit unsure about this one. I know Android has a backup service, but I can't recall the exact details of how to register an app with it. I'll have to think this through step-by-step.
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Beatriz
5 months ago
This seems like a straightforward email send, so I'm leaning towards the Guided Send option. It should give me the right level of control and flexibility for this use case.
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Filiberto
5 months ago
This question is asking about the capabilities of a custom Create action for the Contact object. I'll need to think carefully about the different options and which ones are true.
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Trinidad
5 months ago
I feel pretty confident about this one. The key is that just cause for termination must be based on the employee's conduct or performance, not their protected class status. So A is the correct answer.
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Amina
9 months ago
Who needs speed when you can just sit back and enjoy the slow, steady progress of your query? It's like watching grass grow, but with numbers!
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Tammara
9 months ago
I'm pretty sure the users are just running too many queries at the same time. They need to schedule their queries better!
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Alaine
8 months ago
Data skew from most rows having the same value in the country column might be the issue.
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Elenore
8 months ago
It could be because of NULL values in the state or city columns.
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Annice
8 months ago
Maybe the table has too many partitions causing the slow query.
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Teresita
9 months ago
I think the delay is because of too many concurrent queries.
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Haydee
10 months ago
Hmm, I bet the data is skewed in the country column. Too many rows with the same value would explain the slow performance.
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Val
8 months ago
C) Either the state or the city columns in the [myproject:mydataset.mytable] table have too many NULL values
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Ettie
8 months ago
B) The [myproject:mydataset.mytable] table has too many partitions
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Mariko
8 months ago
C) Either the state or the city columns in the [myproject:mydataset.mytable] table have too many NULL values
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Miesha
8 months ago
B) The [myproject:mydataset.mytable] table has too many partitions
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Gwenn
8 months ago
A) Users are running too many concurrent queries in the system
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Rene
9 months ago
A) Users are running too many concurrent queries in the system
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Eleni
10 months ago
Wow, that's a lot of scan bytes! Maybe the table has too many NULL values in the state or city columns, causing the system to work harder to process all the data.
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Antonio
8 months ago
D) Most rows in the [myproject:mydataset.mytable] table have the same value in the country column, causing data skew
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Shaunna
8 months ago
C) Either the state or the city columns in the [myproject:mydataset.mytable] table have too many NULL values
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Louann
8 months ago
B) The [myproject:mydataset.mytable] table has too many partitions
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Amie
9 months ago
A) Users are running too many concurrent queries in the system
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Nell
9 months ago
D) Most rows in the [myproject:mydataset.mytable] table have the same value in the country column, causing data skew
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Ahmed
9 months ago
C) Either the state or the city columns in the [myproject:mydataset.mytable] table have too many NULL values
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Zana
9 months ago
B) The [myproject:mydataset.mytable] table has too many partitions
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Buddy
10 months ago
A) Users are running too many concurrent queries in the system
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Marvel
10 months ago
The query is slow because there are too many partitions in the table. The data is not distributed evenly, causing the system to work harder to process all the partitions.
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Mammie
9 months ago
B) The [myproject:mydataset.mytable] table has too many partitions
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Wai
9 months ago
A) Users are running too many concurrent queries in the system
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Virgilio
10 months ago
But could it also be because of too many partitions in the table?
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Jaime
11 months ago
I agree with Kiley, data skew can definitely slow down the query.
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Kiley
11 months ago
I think the delay is caused by data skew.
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