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I am writing a batch and using JPA for persistence. I have a table with a lot of records and I need to read all the records by groups of 100 or 500. I don't want to load all the records into memory at once, because there won't be enough memory.

For example:

  • First group: records 1 to 500
  • Second group: records 501 to 1000
  • etc

Is there a better way to do it?

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Vitaly Olegovitch
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1 Answers1

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You should set the first result and the number of results in your javax.persistence.Query with methods setFirstResult() and setMaxResults().

Fortunato
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  • Thank you! I used a variable to use the first result number, initialised to 0. Then I setted the number of max results, and then I made the interrogation to the DB using the query() method. Last thing to do was incrementing the first result by the number of max results of the previous query. – Vitaly Olegovitch Mar 29 '12 at 23:48