Why are interface projections much slower than constructor projections and entity projections in Spring Data JPA with Hibernate?

I experienced similar behavior with an older version of Spring Data and this was my take on it: https://arnoldgalovics.com/how-much-projections-can-help/ I had a talk with Oliver Gierke (Spring Data lead) and he made some improvements (that’s why you get so “good” results 🙂 ) but basically there will be always a cost on having abstractions vs … Read more

How to use $elemMatch on aggregate’s projection?

Quite on old question but literally none of the proposed answers are good. TLDR: You can’t use $elemMatch in a $project stage. but you can achieve the same result using other aggregation operators like $filter. db.itens.aggregate([ { $project: { compList: { $filter: { input: “$complist”, as: “item”, cond: {$eq: [“$$item.a”, 1]} } } } } … Read more

Spring JPA native query with Projection gives “ConverterNotFoundException”

with spring data you can cut the middle-man and simply define public interface IdsOnly { Integer getId(); String getOtherId(); } and use a native query like; @Query(value = “Id, OtherId from TestTable where CreationDate > ?1 and Type in (?2)”, nativeQuery = true) public Collection<IdsOnly> findEntriesAfterDate(Date creationDate, List<Integer> types); check out https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections

What exactly are eye space coordinates?

Perhaps the following illustration showing the relationship between the various spaces will help: Depending if you’re using the fixed-function pipeline (you are if you call glMatrixMode(), for example), or using shaders, the operations are identical – it’s just a matter of whether you code them directly in a shader, or the OpenGL pipeline aids in … Read more

Spring Data JPA Projection selected fields from the DB

If you want use the annotation @Query with Spring Data Projections you have to use field alias and you need to make sure you alias the projects matching the projection fields. The following code should work for question 1: interface PersonRepository extends CrudRepository<Person, Long> { @Query(“select p.firstName as firstname, p.address as address from Person p … Read more

Projecting into KeyValuePair via EF / Linq

Select only columnA and columnB from your table, and move further processing in memory: return context.myTable .Select(o => new { o.columnA, o.columnB }) // only two fields .AsEnumerable() // to clients memory .Select(o => new KeyValuePair<int, string>(o.columnA, o.columnB)) .ToList(); Consider also to create dictionary which contains KeyValuePairs: return context.myTable.ToDictionary(o => o.columnA, o => o.columnB).ToList();

How exactly does OpenGL do perspectively correct linear interpolation?

The output of a vertex shader is a four component vector, vec4 gl_Position. From Section 13.6 Coordinate Transformations of core GL 4.4 spec: Clip coordinates for a vertex result from shader execution, which yields a vertex coordinate gl_Position. Perspective division on clip coordinates yields normalized device coordinates, followed by a viewport transformation (see section 13.6.1) … Read more

Calculating a LookAt matrix

Note the example given is a left-handed, row major matrix. So the operation is: Translate to the origin first (move by –eye), then rotate so that the vector from eye to At lines up with +z: Basically you get the same result if you pre-multiply the rotation matrix by a translation –eye: [ 1 0 … Read more

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