java - Why does this result in non-lazy fetching and N+1 select statements? -

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I just hope to have a SQL query, but I'll go to the N + 1 selected network. I really do not understand why there is a problem in detail here:

I have a unit "player": 

  @inti @Table (name = " Player_ref ") Public class PlayerRef {// constructor etc ... @OptimasticalLock (removed = true) @OneToMany (fetch = FetchType.LAZY, mapped =" player ") public set & lt; Player & gt; Millplayer () {Return Player; }}

and a class player: 

  @Entity @Table (name = "player") public class player {// constructor etc ... @OptimisticLock (excluded = true) @ManyToOne (optional = true, bringing = FetchType.LAZY) @JoinTable (name = "cr_player_ref_player", joinColumns = {@JoinColumn (name = "player_id", unique = true)}, inverseJoinColumns = {@JoinColumn} Public player Reef Miller () {This return player.}}

Now, in my program I use the following HQL query to all playerRef entities To get: 

  query playerRefQ = session.createQuery ( "playerRef choose Pleyrrf Kiladhirf from") .setReadOnly (true); PlayerRefQ.setParameter ( "game", game); @SuppressWarnings ( "unchecked") List & lt; PlayerRef & gt; AllPlayerRefs = PlayerRefQ.list ();

It selects statements in N + 1:

1) 

  select playerref0_ as .id id1_21_, playerref0_ .. .. player_ref playerref0_  and

n time) 

  players0_.player_ref_id player_r1_21_0_, player_i2_34_0_ as players0_.player_id, Select as id1_19_1_finders1_.id, player1_. ..., as player1_1_.player_ref_id player_r1_34_1_, ... from cr_player_ref_player on players0_ the inner join players0_.player_id = player1_.id player player1_ external player1_.id = player1_1_.player_id where joining players0_.player_ref_id = cr_player_ref_player player1_1_ Left for?

Since I thought the collection should be a hibernate-proxy lazy load and each player has a set of players, it's very unpredictable.

Does anyone know how can I actually load players' reef units without loading them? In the case of my use I need all the players, but not related players.

The problem came from here, that your underlying DB structure is actually several-to- Many is a pair table cr_player_ref_player , and that means, that

  • a player can be multiple PlayerRef < / Li>
  • You can see many players

in a player

instead: < / P> 

  Public player Reef Millpler () {This return player. }

should be there: 

  public set & lt; PlayerRef & gt; GetPlayerRefs () {Returns player; } Confusion for  Hibernate  comes from:  @OneToMany (fetch = FetchType.LAZY, mappedBy = "playerRef")  , Primarily that mapping will be found under the  "playerRef"  ... ... where the required  is more complex and partially than expected Is expressed  many-to-many . And that's why we can see these weird N + 1s ...

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