KeysetScrollPosition.isInitial always returns false

[wsaca]

Hello, I have a problem trying to check if my query is in the first position:

Window<Role> findAllBy(ScrollPosition position);

When calling it, it returns 2 records:

Window<Role> window = roleRepository.findAllBy(ScrollPosition.keyset());

but window.positionAt(0).isInitial() always returns false

The reason apparently lies in the JpaMetamodelEntityInformation.getKeyset method which always returns at least one key set:

spring-data-jpa/spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/JpaMetamodelEntityInformation.java

Line 233 in 1b50d23

public Map<String, Object> getKeyset(Iterable<String> propertyPaths, T entity) {

getKeyset is used in ScrollDelegate.createWindow:

spring-data-jpa/spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/ScrollDelegate.java

Line 89 in 1b50d23

Map<String, Object> keys = entity.getKeyset(sort.stream().map(Order::getProperty).toList(), object);

and by calling window.positionAt(0).isInitial(), the KeysetScrollPosition.isInitial method checks the loaded keys where it always finds at least one and returns false:
https://github.com/spring-projects/spring-data-commons/blob/30dcacc8c1ef11d70580f7f79927122590a71ac7/src/main/java/org/springframework/data/domain/KeysetScrollPosition.java#L140

[quaff]

The javadoc of ScrollPosition.isInitial() states:

Returns whether the current scroll position is the initial one.

The javadoc of Window.positionAt() states:

Returns the {@link ScrollPosition} at {@code index}.

It doesn't state position at zero must be initial one, I don't think it's a bug.
Could you share your actual use case to check ScrollPosition.isInitial() ?

[mp911de]

What @quaff said. Conceptually, the initial position starts before index zero as it describes the position before the first element.

Regardless of keyset or offset mechanisms, if you request the next Window as of previous.positionAt(0) then the next window starts after the first element of the initial window of data.