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Editorial Team
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Asked: 2026-05-23T17:31:30+00:00

I’m struggling to improve a n+1 query on a project I’m working on. I

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I’m struggling to improve a n+1 query on a project I’m working on. I use Hibernate with the model shown below, and I want to express a query to retrieve all items related to a portfolio, including the last two prices on each item (price on given date and previous price).

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Example API:

List<Items> items = findItemsWithLatestTwoPrices(portfolio, latestPriceDate);

Currently I use one query to extract all items related to the portfolio, and then I iterate over those items to query the two latest prices on a given item (so n+1).

I tried expressing this in native sql using a correlated subquery , but the performance was terrible. This and the fact that there are new prices every day (so the query is getting slower) has lead me to think I need a different model, but I’m struggling to come up with a model that is reasonably effective and constant over time as number of prices increase.

I’ve been thinking about different solutions including representing prices as linked lists, or using some sort of tree but I believe there are better alternatives. Am I missing something obvious? Has anyone working on a similar problem come up with at good solution?

I don’t really care wether I use HQL or native SQL as long as the performance is decent. I’m also open to make changes to the model.

Thanks!

[Edit]

Since I have over two years of price data, and there can be 1000+ items pr. portfolio, retrieving the entire graph is probably not a good idea. Also I need random access by date, so storing the two prices as fields on the item is unfortunately not an option.

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1 Answer

  1. Editorial Team

    Not sure I´m catching all your concerns, but like you´ve probably figured, there´s no easy solution to this with Hibernate. It will come down to your modeling of the domain. I think you´re best to separate the normal case and the special case. You can model them in your normal domain, or use special representations for the special cases.

    For fetching the n latest prizes have you tried setting the batch size on the relation? Make the relation ordered (latest on top), and then set the batch-size to something like 10. That would make Hibernate query for 10 and 10 rows, and with indices on the foreign key and the order column it should perform ok in most cases.

    It also seems to me you could keep extra relations as well as the entire set. Don´t be afraid of explicitly model important relationships like “last months prices”, even though it would be duplication of data. It should be possible to avoid duplication in the DB in most cases.

    For your random access based on dates it sounds like you´re best served with a custom query instead of access through the domain model, if they´re too slow consider using second level caching, but I´m guessing that your access pattern won´t benefit much from this.

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