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Re: [eclipselink-users] fetch size setting without effect
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I think the issue is the nested query is already prepared, so you need to set
the fetch size into the call, instead of the query.
q.getCall().setResultSetFetchSize(5000);
Thomas Paradies-2 wrote:
>
> Hi,
>
> it seems that fetch size setting at an embedded batch query wouldn't have
> the expected effect.
>
> To demonstrate the issue I've constructed a very simple szenario with two
> entities A and B with an One(A)ToMany(B) relationship between them.
>
> @Entity @Table(name = "T0")
> public class A {
> @Id @Column(name = "A_ID")
> private long id;
>
> @OneToMany(mappedBy = "a")
> private List bs;
>
> public List getBs() { return bs; }
> }
>
> @Entity @Table(name = "T1")
> public class B {
> @Id @Column(name = "B_ID")
> private long id;
>
> @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "A_ID")
> private A a;
>
> public A getA() { return a; }
> }
>
> The code fragment below shows two findAll methods - one should retrieve
> all As and as result all related Bs and the other should get all Bs with
> all related As (but just lazy).
> ....
> public List findAllAs() {
> ReadAllQuery query = new ReadAllQuery(A.class);
> query.setFetchSize(500);
> query.addBatchReadAttribute(builder.get("bs"));
> query.prepareCall(getServerSession(), null);
> Map map = query.getBatchReadMappingQueries();
> if (map != null) {
> for (Object key : map.keySet()) {
> if (key.equals("bs")) {
> ReadAllQuery q = (ReadAllQuery) map.get(key);
> q.setFetchSize(5000);
> }
> }
> }
> List as = (List ) getServerSession().executeQuery(query);
> return as;
> }
>
> public List findAllBsForAs() {
> ReadAllQuery query = new ReadAllQuery(B.class);
> query.setFetchSize(5000);
> query.prepareCall(getServerSession(), null);
> List bs = (List) getServerSession().executeQuery(query);
> return bs;
> }
> ....
>
> With the profiling done for each of the methods using PerformanceProfiler
> and EclipseLink log I got the following outputs (for clarification only
> the relevant parts are shown)
>
> - for findAllAs() the profiler output for embedded batch query
> ....
> Begin profile of{ReadAllQuery(com.mons.entity.B)
> [EL Fine]: 2008.10.17 09:46:59.422--Connection(26188661)--SELECT t0.B_ID
> FROM T0 t0, T1 t1 WHERE (t0.A_ID = t1.A_ID)
> Profile(ReadAllQuery,
> class=com.mons.entity.B,
> number of objects=4721,
> total time=33733,
> local time=33733,
> profiling time=16,
> row fetch=33139,
> object building=267,
> cache=111,
> logging=32,
> sql execute=265,
> time/object=7,
> objects/second=139,
> )
> }End profile
> ....
>
> - for findAllBsForAs() the profiler output for main query
> ....
> Begin profile of{ReadAllQuery(com.mons.entity.B)
> [EL Fine]: 2008.10.17 09:49:33.102--Connection(19351067)--SELECT t0.B_ID
> FROM T0 t0, T1 t1 WHERE (t1.A_ID = t0.A_ID))
> Profile(ReadAllQuery,
> class=com.mons.entity.B,
> number of objects=4721,
> total time=1530,
> local time=1530,
> cache=173,
> sql prepare=172,
> row fetch=63,
> sql execute=921,
> object building=343,
> logging=31,
> objects/second=3085,
> )
> ....
>
> The query string for findAllAs() equals the query string of
> findAllBsForAs() and the fetch size setting is even for both of them.
> Nevertheless the "row fetch" value in the profile of the batch query is
> 33139 (near 33733 for "total time" so I'm assuming the unit is ms) but
> only 63 (1530 total) for the direct query. With an fetch size of 5000 for
> 4721 retrieved objects the second value but not the first is as I would
> expecting...
>
> My question is: Am i doing something wrong, am I missing something, or
> maybe this is a bug?
>
> I'm grateful for any idea or suggestion,
>
> Thomas
>
>
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http://wiki.eclipse.org/User:James.sutherland.oracle.com James Sutherland
http://www.eclipse.org/eclipselink/
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