I´m working on this project that process a user request and generate a report on csv format.
The data is read from a Postgres 15.2 DB. I´m using Springbatch where I use a JdbcCursorItemReader<Map<String, Object>> to retrieve data from a Postgres Function.

@Bean
@StepScope
public JdbcCursorItemReader<Map<String, Object>> rptReader(
        @Value("#{jobParameters['functionName']}") String functionName,
        @Value("#{jobParameters['costCenterId']}") Long costCenterId,
        @Value("#{jobParameters['startDate']}") LocalDate startDate,
        @Value("#{jobParameters['endDate']}") LocalDate endDate) {

    // new Object[] { costCenterId.intValue(), startDate, endDate }))
    log.info("RUNNING {}", functionName);
    try {
        log.info("AUTOCOMMIT VALUE {}", dataSource.getConnection().getAutoCommit());
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return new JdbcCursorItemReaderBuilder<Map<String, Object>>()
            .dataSource(dataSource)
            .name("reader")
            .preparedStatementSetter(new ArgumentPreparedStatementSetter(
                    new Object[] { costCenterId.intValue(), startDate, endDate }))
            .sql(buildFunction(functionName))
            .fetchSize(100)
            .rowMapper(new ColumnMapRowMapper())
            .build();

}
private String buildFunction(String functionName) {
    var sql = new StringBuilder();
    sql.append("SELECT * FROM ");
    sql.append(functionName);
    sql.append(" (?,?,?)");
    return sql.toString();
}

I´m getting java.lang.OutOfMemoryError: Java heap space, and it seems this 1.2 million data is loaded in memory.
It seems, when using fetchSize against a Postgres function does not work. However, I have extracted the query from the function and ran without any issue.
Anyone has experience such scenario? If you did, can you shared yours thoughts?
I´m not an expert on Postgres Function, but I´m trying to change it to use cursor.
The spring version I´m using is 3.3.2