Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p><strong>Ad. A</strong>: Looks like you are aware what <code>clear()</code> does. The reason to call it explicitly is to remove all managed entities from L1 cache, so that it does not grow infinitely when processing large data sets in one transaction.</p> <p>It discards all the changes that were made to managed entites <strong>not explicitly persisted</strong>. This means that you can safely modify an entity, update it explicitly and clear the session. This is the <em>right</em> design. Obviously if no changes are made (long, but read only session), <code>clear()</code> is always safe.</p> <p>You can also use <a href="http://docs.jboss.org/hibernate/core/3.3/reference/en/html/batch.html" rel="noreferrer">stateless sessions</a>.</p> <p><strong>Ad. B</strong>: No, it exists for the reasons above: to make sure L1 (session cache) does not grow too much. Of course maintaining it manually is a poor idea and an indication that another tool should be used for large data sets, but sometimes it is a must.</p> <p>Note that in JPA specification there is also <code>clear()</code> and <code>flush()</code> method. In this case you should always call <code>flush()</code> first to push changes into the database (explicit update) prior to calling <code>clear()</code>.</p> <p><strong>Ad. C</strong>: It's actually a good idea to warn the user (maybe by issuing warning message rather than throwing an exception) when he/she clears the session with dirty changes. Also I don't think a <em>framework</em> code should call <code>clear()</code> unconditionally, unless it is sure that the user code it runs flushes or does not make any changes.</p>
    singulars
    1. This table or related slice is empty.
    1. POorg.hibernate.Session.clear() considered Harmful?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USTomasz Nurkiewicz
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POorg.hibernate.Session.clear() considered Harmful?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COad A): Processing large datasets in one transaction sounds like bad design to me (granted, I might not have thought of all possible Problems...). What do you mean by "explicitly" persisting an entity? session.save(entity)? Ad C): Sounds like we agree frameworks should not do this - the framework can't possibly be sure what clients do. :-)
      singulars
      1. PO
      1. USMorten Lauritsen Khodabocus
    2. CO@MortenLauritsenKhodabocus: obviously, loading and modifying thousands of records in one Hibernate transaction is a sign that a different tool should be used. Yes, by *explicitly* I mean calling `save()` as opposed to letting Hibernate to discover dirty entities.
      singulars
      1. PO
      1. USTomasz Nurkiewicz
    3. CO@MortenLauritsenKhodabocus Please enlighten me. Why would it be a bad idea to process a large read-only data set in one Transaction? It seems to me that if it involved ordering on the DB side, it would be smart because it would save from needing to reorder multiple times. Doesn't using a transaction mean the DB will remember your ordered state across different queries that are part of the same transaction? Also, isn't 'using one Transaction' exactly what Hibernate's ScrollableResults API does?
      singulars
      1. PO
      1. USKyleM
 

Querying!

 
Guidance
A row detail

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.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload