How to test if a table is empty, using Hibernate

Question

Using Hibernate, what is the most efficient way to determine if a table is empty or non-empty? In other words, does the table have 0, or more than 0 rows?

I could execute the HQL query select count(*) from tablename and then check if result is 0 or non-0, but this isn't optimal as I would be asking the database for more detail than I really need.

Brian Deterling · Accepted Answer · 2010-05-28 22:59:06Z

4

A lot of databases are efficient at returning a count of records in a table, but if you want to be creative, how about session.createQuery("select 1 from table").setMaxSize(1).list().isEmpty()?

Or: session.createQuery("select 1 from table").setFetchSize(1).scroll(ScrollMode.FORWARD_ONLY).next() == null

I think it will depend on the database as to which method is the fastest.

answered May 28, 2010 at 22:59

Brian Deterling

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Mark Byers · Accepted Answer · 2010-05-28 21:39:37Z

3

The following SQL is a very efficient way to see if a table contains a row:

SELECT EXISTS (SELECT NULL FROM tablename)

I'm not sure how to convert it to HQL - maybe it just works?

edited May 28, 2010 at 21:39

answered May 28, 2010 at 21:27

Mark Byers

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