[EMAIL PROTECTED] wrote:
Armin,
I'm using 1.0.4.
I am not doing a QueryByIdentity. I am doing a QueryByCriteria. So when
I do:
QueryByCriteria query = QueryFactory.newQuery(Article.class,
criteria, true);
broker.getCollectionByQuery(query);
my expectation would be that the SQL generated would be:
-- Which Identities match my criteria?
select distinct Artikel_Nr from Artikel where ...
-- for cache misses:
select Artikel_Nr, Artikelname, Lieferanten_Nr, ... from Artikel
where Artikel_Nr = ?
This isn't the query/cache-strategy of OJB, because in this case the
cache should match most objects from the database (this would require a
really big cache), else we will get many single select statements for
the missed objects in cache.
But instead, here's what happens:
-- Which Identities match my criteria?
select distinct Artikel_Nr, Artikelname, Lieferanten_Nr, ... from
Artikel where ...
-- for cache misses:
select Artikel_Nr, Artikelname, Lieferanten_Nr, ... from Artikel
where Artikel_Nr = ?
This isn't the strategy of OJB. First OJB execute the distinct query,
then OJB loop through the result set read the Identity of the row and
check for cache match. If true the object will be read from cache, else
the whole object will be materialized from result set row.
When all of the irrelevant columns are included in the first query, that
query slows down dramatically. So what I'm wondering is why the first
query includes all of these columns that it doesn't need, rather than just
retrieving the PKs?
See above.
...
> millions of rows in my result set; afterwards, I have about 700. If I
> query just for the PK, the query takes a few seconds to return the 700
> PK
...
You could do that in two steps:
First use a ReportQuery to retrieve all PK's (e.g. with
PB.getReportQueryIteratorByQuery(q) or getCollectionByQuery), then use
PB.getObjectByIdentity(...) to materialize the object.
In this case the worst case scenario would execute 701 select statements
to materialize the objects (if you use the two-level cache and none-lazy
references, OJB will need additional queries to lookup the referenced
objects).
http://db.apache.org/ojb/docu/guides/query.html#Report+Queries
http://db.apache.org/ojb/docu/tutorials/pb-tutorial.html#Find+object+by+primary+key
regards,
Armin
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