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POJpa , Hibernate select query optimization
 

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  1. POJpa , Hibernate select query optimization
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    <p>I am new to JPa / Hibernate. We are using JPA with hibernate in our application. Currently i observed that performing select query on table with criteria, hibernate perform select query for each row.</p> <p>So my question is , how hibernate perform search on table and retrieves records ?</p> <p>I have a scenario where i need to find active users and perform filers on active user list , like recently logged in users, most popular user(based on some criteria) for example i have 100 active users of which 20 users are recently logged in. 20 users are most popular.</p> <p>if i have to fetch records from database , when i query with active users , hibernate perform 100 select operations.(with table scan)</p> <p>and if i perform 2 seperate queries for recent and most popular users hibernate will perform 20 + 20 = 40 select operations. (but with 2 times table scan)</p> <p><strong>so how hibernate fetches records from database ?</strong> if i compare with jdbc , i would say by getting active pitches and performing filters on it i will be doing 1 time table scan.</p> <p>but with hibernate it performs more select operations and it queries less select when i do individual selects for recent and most popular users ,even when i do 2 time table scan !</p> <pre><code>@ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "fk_profile_id", referencedColumnName = "pk_id") private Profile Profile; @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "investmentPitch", targetEntity = InvestmentType.class, orphanRemoval = true) private List&lt;InvestmentType&gt; investmentType; @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "investmentPitch", targetEntity = TabDetail.class, orphanRemoval = true) private List&lt;TabDetail&gt; TabDetail; @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "investmentPitch", targetEntity = Address.class, orphanRemoval = true) private List&lt;Address&gt; Address; @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.DETACH) @JoinTable(name = "pitch_sector", joinColumns = { @JoinColumn(name = "fk_id", nullable = false, updatable = false) }, inverseJoinColumns = { @JoinColumn(name = "fk_sector_id", nullable = false, updatable = false) }) private List&lt;SectorMaster&gt; sectors; </code></pre>
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    1. COCould you please post your mappings and classes. Hibernate definitly doesn't retrieve every record with a single select. There must be some mapping (for example one to many) that is loaded for every single record after the record list is loaded.
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    2. COi have updated my mapping objects ... it mainly has oneToMany and ManyToMany relations... when i perform select on above mentioned table (investmentPitch) it queries every single record with select query
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    3. COFetchType.EAGER will load things on initialisation, generally, this is not what you want to be doing.
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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