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1000 select queries vs 1 ( select .. in ) query
Posted by: Ngọc Nguyễn
Date: May 04, 2021 10:15AM

Hello.
I have just read about N+1 queries problem. So I have the doubt about the performance of 2 ways.
The way 1: I have 1000 queries like that:
select * from topic where user_id = 1
select * from topic where user_id = 2
...

select * from topic where user_id = 1000

I supposed the topic table has 1.000.000 rows and each query uses binary search, so I think the Big O's way is: 1000 * log2(1.000.000)

The way 2: I have 1 query:
select * from topic where user_id in (1,2,..., 1000)

I don't know the algorithm of 2nd way. So can you explain me the algorithm of (select .. in) query. Is there any case the 1st way is better than 2nd way?

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May 04, 2021 10:15AM


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