Re: [eclipselink-users] batch reading with separate fetch size setting

[James Sutherland <jamesssss@xxxxxxxxx>]

There is no query hint to do this, feel free to log an enhancement request
for this.

You can configure this using the ReadAllQuery code API.



Kate Lain wrote:
> 
> James,
> 
> I have three related entities say A, B, C with an OneToMany mapping both
> between A - B and A - C . There is a need to read all the objects in a
> single query. Therefore i've defined a named query in A as follows:
> 
> @NamedQuery(
>     name = "A.findAll", 
>     query = "SELECT a FROM A a , 
>     hints = { 
>         @QueryHint(name = QueryHints.BATCH, value = "a.bs"),
>         @QueryHint(name = QueryHints.BATCH, value = "a.cs"),
>         @QueryHint(name = QueryHints.JDBC_FETCH_SIZE, value = "500")
>     }
> )
> 
> As result I got about 500 objects for A, 5000 objects for B and 50000
> objects for C from the three queries (the one named and the two batch
> queries). Regarding the tuning of the jdbc fetch size I can only define a
> single value as query hint as far as I can gather. I take it that it will
> only taking effect for the A-query wouldn't it? How may I effect then the
> fetch size for the batch queries. Or, I'm totally wrong here?
> 
> --- On Thu, 10/2/08, James Sutherland <jamesssss@xxxxxxxxx> wrote:
> From: James Sutherland <jamesssss@xxxxxxxxx>
> Subject: Re: [eclipselink-users] batch reading with separate fetch size
> setting
> To: eclipselink-users@xxxxxxxxxxx
> Date: Thursday, October 2, 2008, 6:57 AM
> 
> I'm not exactly sure I understand what you mean perhaps give an example.
> 
> Assuming you want to set the fetch size of the nested batch queries, there
> is no easy way to do this.  However you could prepare() your query, then
> access the getBatchReadMappingQueries() that are generated to customize
> any
> of the nested batch queries.
> 
> 
> 
> Kate Lain wrote:
>> 
>> Hi,
>> 
>> 
>> 
>> for performance reasons I've optimized my queries using batch reading
>> and fetch size tuning - but is there a way to set the fetch size separate
>> per
>> batch query?
>> 
>> Thomas
>> 
> 


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