Right, this is related to pagination. All I'm saying is that if I have
100,000 results (not necessarily blobs) and I only want to pick up the
first five results, I should be able to do just that. Hitting all
100,000 results when I know in advance I will not read them is a huge
waste of both memory and time.
Regarding my suggestion, the default would be the current behavior
(i.e. retrieve all values) but I'm saying it would be nice to have the
option to tweak this further. To my understanding, even with Pagination,
Cayenne will retrieve all primary keys from a result. I saw an open JIRA
issue for this I think.
Gili
Gentry, Michael (Contractor) wrote:
> I really can't imagine my to-many faults not returning everything in the
> relationship. I certainly wouldn't want it to only fault in what I try
> to read (that would require far too many SELECTs and hurt performance).
> And it's probably too arbitrary to pick N records for it to read in at a
> time.
>
> Given your example, it still seems like you are still having your BLOB
> data inside a table with other data instead of isolated. So, when you
> fault your to-many relationship, you are getting all of the BLOB data (N
> rows) in addition to the other attributes. This is almost always going
> to be a lose situation using ORM.
>
> All that being said, perhaps a paginated query could help you out?
>
> http://www.objectstyle.org/cayenne/userguide/perform/paged-queries.html
>
> /dev/mrg
>
> -----Original Message-----
> From: Gili [mailto:cowwo..bs.darktech.org]
> Sent: Monday, September 05, 2005 3:29 AM
> To: cayenne-deve..bjectstyle.org
> Subject: Idea for index/limit support
>
>
>
> Aside from the obvious idea that queries should be able to set
> index/limit, I'm thinking we should modify the behavior of relationship
> getting methods. Currently they return a List from xxxArray
> relationships. I'm thinking we should implement the List interface, and
> provide special index/limit/fetchSize methods in our implementation.
> This way old code continues working as is and new code that wishes to
> optimize performance does something like this:
>
> List images = dataObject.getImageArray();
> CayenneList typedImages = (CayenneList) images;
>
> // (optional) configure List before using it
> typedImages.setFetchSize(10);
> typedImages.setMinIndex(15);
> typedImages.setMaxIndex(30);
>
> // use list like we always did
> typedImages.get(20);
>
> now... min/max indexes are hints to the List implementation as
> to what
> index/limit values to issue the query with. If a user tries to get() an
> index outside this range we will issue a second query but this is
> unlikely to happen. The typical usage scenerio would be if the above had
>
> 100,000 rows in the result we'd see a noticable performance benefit of
> only retrieving 15 rows (index 15 - 30 inclusive). And best of all, this
>
> change is completely backwards compatible with older releases. What do
> you think?
>
> Gili
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