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


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:

    name = "A.findAll",
    query = "SELECT a FROM A a ,
    hints = {
        @QueryHint(name = QueryHints.BATCH, value = ""),
        @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

--- James Sutherland
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