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POWhy is the Hibernate query.list() slow?
 

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  1. POWhy is the Hibernate query.list() slow?
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    <p>I am using Hibernate 4.1.6 and having issues with the speed that a list is built. I am running the following query.</p> <pre><code>public void doQuery(final Baz baz){ final Query query = getSessionFactory().getCurrentSession().createQuery( "select c.id, foo.someValue from Foo as foo "+ "join foo.a as a"+ "join foo.b as b "+ "join b.c as c "+ "where baz=:baz" ); query.setParameter("baz", baz); Long start=System.currentTimeMillis(); final List&lt;Object[]&gt; list = query.list(); Long end=System.currentTimeMillis(); System.out.println((end-start)); } </code></pre> <p>I set hibernate debugging on to get the actual query that is sent to the database. I ran that query directly in the database and it returned 23,000 rows in 0.015 ms. So, I'm guessing the query is not the issue. The example above shows it takes ~ 32 seconds to create that list. Is there something that can be done to speed that up?</p> <p>Update: I tried using the createSQLQuery() method using the hibernate debugging query and it ran just as slow as the createQuery() method.</p> <p>Update: I tried using a stateless session but it ran just as slow.</p> <p>Update: I outputted some statistics (setting the hibernate.generate_statistics flag to true) but nothing looks alarming to me:</p> <pre><code>Hibernate SessionFactory Statistics [ Number of connection requests[4] Number of flushes done on the session (either by client code or by hibernate[3] The number of completed transactions (failed and successful).[3] The number of transactions completed without failure[3] The number of sessions your code has opened.[4] The number of sessions your code has closed.[3] Total number of queries executed.[4] Time of the slowest query executed.[28258] the number of collections fetched from the DB.[6] The number of collections loaded from the DB.[6] The number of collections that were rebuilt[0] The number of collections that were 'deleted' batch.[0] The number of collections that were updated batch.[0] The number of your objects deleted.[0] The number of your objects fetched.[1] The number of your objects actually loaded (fully populated).[204] The number of your objects inserted.[1] The number of your object updated.[0] ] Hibernate SessionFactory Query Statistics [ total hits on cache by this query[0] total misses on cache by this query[0] total number of objects put into cache by this query execution[0] Number of times this query has been invoked[1] average time for invoking this query.[28258] maximum time incurred by query execution[28258] minimum time incurred by query execution[28258] Number of rows returned over all invocations of this query[23303] ] </code></pre> <p>Update: I see the same slowness when doing a next() from a ScrollableResults from a native query. Note that I am doing nothing in the loop. </p> <pre><code> ScrollableResults results = query.scroll(); Long start=System.currentTimeMillis(); while (results.next()) { //do nothing } Long end=System.currentTimeMillis(); System.out.println((end-start)); </code></pre>
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      1. POWhy is the Hibernate query.list() slow?
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    1. COCould be an uncommited transaction holding up the works.
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      1. USPeter Bratton
    2. COYou may want to print out your hibernate sql. Most likely have an n+1 select issue.
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      1. USJohn Vint
    3. COJordan, I don't know of any transactions holding up this query. John, I did print out the sql as mentioned above and the query is fine.
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