NullPointerException when using Base Query with window functions

[sleepkqq]

Problem Description

I'm getting a NullPointerException when trying to use Jimmer's base query feature with window functions for implementing a leaderboard with pagination:

java.lang.NullPointerException: Cannot invoke "org.babyfish.jimmer.sql.ast.impl.table.StatementContext.allocateTableAlias()" because "stmtCtx" is null
	at org.babyfish.jimmer.sql.ast.impl.table.RealTableImpl.allocateAliasImpl(RealTableImpl.java:804)
	at org.babyfish.jimmer.sql.ast.impl.table.RealTableImpl.allocateAliases(RealTableImpl.java:768)
	at org.babyfish.jimmer.sql.ast.impl.query.UseTableVisitor.allocateAliases(UseTableVisitor.java:28)
	at org.babyfish.jimmer.sql.ast.impl.query.ConfigurableRootQueryImpl.preExecute(ConfigurableRootQueryImpl.java:385)
	at org.babyfish.jimmer.sql.ast.impl.query.ConfigurableRootQueryImpl.executeImpl(ConfigurableRootQueryImpl.java:317)
	...
	at org.babyfish.jimmer.sql.ast.query.ConfigurableRootQuery.fetchPage(ConfigurableRootQuery.java:70)

Code

I'm following the base query documentation and trying to implement a paginated leaderboard query:

public Page<? extends Tuple3<LeaderboardUserView, ? extends Number, Integer>> getLeaderboardPage(
    LeaderboardType type,
    @Nullable LocalDate day,
    int page,
    int size
) {
  var u = USER_TABLE;

  Expression<? extends Number> expression;
  Predicate predicate;

  switch (type) {
    case TASKS -> {
      var pt = PLAYER_TASK_TABLE;

      var query = sql.createSubQuery(pt)
          .where(
              pt.player().id().eq(u.id()),
              pt.status().eq(PlayerTaskStatus.COMPLETED)
          );

      if (day != null) {
        var utc = ZoneId.of("UTC");
        var startOfDay = day.atStartOfDay(utc).toInstant();
        var endOfDay = day.plusDays(1).atStartOfDay(utc).toInstant();

        query = query.where(
            pt.updatedAt().ge(startOfDay),
            pt.updatedAt().lt(endOfDay)
        );
      }

      var taskCount = query.selectCount();
      expression = taskCount;
      predicate = taskCount.gt(0L);
    }

    case CURRENCY -> {
      var balance = u.player().balance().balance();
      expression = balance;
      predicate = balance.gt(BigDecimal.ZERO);
    }

    case LEVEL -> {
      expression = u.player().level().level();
      predicate = null;
    }

    default -> throw new IllegalArgumentException("Unknown leaderboard type: " + type);
  }

  var baseUser = sql.createBaseQuery(u)
      .where(predicate)
      .addSelect(u)
      .addSelect(expression)
      .addSelect(
          Expression.numeric().sql(
              Integer.class,
              "row_number() over(order by %e desc, %e asc)",
              expression,
              u.id()
          )
      )
      .asBaseTable();

  return sql.createQuery(baseUser)
      .select(
          baseUser.get_1().fetch(LeaderboardUserView.class),
          baseUser.get_2(),
          baseUser.get_3()
      )
      .fetchPage(page, size);
}

Questions

1. Is this approach correct? Am I using the base query API correctly with asBaseTable() and subsequent createQuery()?

2. Is this a bug or incorrect usage? The NPE in StatementContext.allocateTableAlias() suggests that the statement context is null when trying to execute the query. Should I open an issue for this, or is there a correct pattern I'm missing?

Environment

• Jimmer version: 0.9.115
• Database: PostgreSQL
• Spring Boot version: 3.5.7

Any guidance would be appreciated!