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JPA @OneToMany LAZY Fetch vs EAGER Fetch

Posted on

FetchType.LAZY

csongyu/jpa-fetch

branch: feature/FetchType.LAZY

where company_code=?

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Hibernate: 
    select
        company0_.code as code1_1_0_,
        company0_.name as name2_1_0_ 
    from
        company company0_ 
    where
        company0_.code=?
Hibernate: 
    select
        employees0_.company_code as company_4_2_0_,
        employees0_.id as id1_2_0_,
        employees0_.id as id1_2_1_,
        employees0_.code as code2_2_1_,
        employees0_.company_code as company_4_2_1_,
        employees0_.name as name3_2_1_ 
    from
        employee employees0_ 
    where
        employees0_.company_code=?

where company_code in (?,?)

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Hibernate: 
    select
        company0_.code as code1_1_,
        company0_.name as name2_1_ 
    from
        company company0_ 
    where
        company0_.code in (
            ? , ?
        )
Hibernate: 
    select
        employees0_.company_code as company_4_2_0_,
        employees0_.id as id1_2_0_,
        employees0_.id as id1_2_1_,
        employees0_.code as code2_2_1_,
        employees0_.company_code as company_4_2_1_,
        employees0_.name as name3_2_1_ 
    from
        employee employees0_ 
    where
        employees0_.company_code=?
Hibernate: 
    select
        employees0_.company_code as company_4_2_0_,
        employees0_.id as id1_2_0_,
        employees0_.id as id1_2_1_,
        employees0_.code as code2_2_1_,
        employees0_.company_code as company_4_2_1_,
        employees0_.name as name3_2_1_ 
    from
        employee employees0_ 
    where
        employees0_.company_code=?

FetchType.EAGER

csongyu/jpa-fetch

branch: feature/FetchType.EAGER

where company_code=?

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Hibernate: 
    select
        company0_.code as code1_1_0_,
        company0_.name as name2_1_0_,
        employees1_.company_code as company_4_2_1_,
        employees1_.id as id1_2_1_,
        employees1_.id as id1_2_2_,
        employees1_.code as code2_2_2_,
        employees1_.company_code as company_4_2_2_,
        employees1_.name as name3_2_2_ 
    from
        company company0_ 
    left outer join
        employee employees1_ 
            on company0_.code=employees1_.company_code 
    where
        company0_.code=?

where company_code in (?,?)

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Hibernate: 
    select
        company0_.code as code1_1_,
        company0_.name as name2_1_ 
    from
        company company0_ 
    where
        company0_.code in (
            ? , ?
        )
Hibernate: 
    select
        employees0_.company_code as company_4_2_0_,
        employees0_.id as id1_2_0_,
        employees0_.id as id1_2_1_,
        employees0_.code as code2_2_1_,
        employees0_.company_code as company_4_2_1_,
        employees0_.name as name3_2_1_ 
    from
        employee employees0_ 
    where
        employees0_.company_code=?
Hibernate: 
    select
        employees0_.company_code as company_4_2_0_,
        employees0_.id as id1_2_0_,
        employees0_.id as id1_2_1_,
        employees0_.code as code2_2_1_,
        employees0_.company_code as company_4_2_1_,
        employees0_.name as name3_2_1_ 
    from
        employee employees0_ 
    where
        employees0_.company_code=?

JOIN FETCH

csongyu/jpa-fetch

branch: feature/JOIN-FETCH

where company_code=?

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Hibernate: 
    select
        company0_.code as code1_1_0_,
        employees1_.id as id1_2_1_,
        company0_.name as name2_1_0_,
        employees1_.code as code2_2_1_,
        employees1_.company_code as company_4_2_1_,
        employees1_.name as name3_2_1_,
        employees1_.company_code as company_4_2_0__,
        employees1_.id as id1_2_0__ 
    from
        company company0_ 
    inner join
        employee employees1_ 
            on company0_.code=employees1_.company_code 
    where
        company0_.code=?

where company_code in (?,?)

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Hibernate: 
    select
        company0_.code as code1_1_0_,
        employees1_.id as id1_2_1_,
        company0_.name as name2_1_0_,
        employees1_.code as code2_2_1_,
        employees1_.company_code as company_4_2_1_,
        employees1_.name as name3_2_1_,
        employees1_.company_code as company_4_2_0__,
        employees1_.id as id1_2_0__ 
    from
        company company0_ 
    inner join
        employee employees1_ 
            on company0_.code=employees1_.company_code 
    where
        company0_.code in (
            ? , ?
        )

@OneToMany N+1 SELECT

QUERIES FetchType.LAZY FetchType.EAGER JOIN FETCH
where company_code=? 2 1 1
where company_code in (?,?) 3 (N+1) 3 (N+1) 1