pgjdbc: Setting the fetch size on a CallableStatement does not work.

Setting the fetch size on a CallableStatement does not work, when reading the resultset the default fetch size is used. If the default fetch size (that can be configured with the driver property ‘defaultRowFetchSize’) is left to its default value 0 (load the entire resultset), for CallableStatements, regardless of the fetch size set on the statement the entire resultset is loaded in memory. A heap dump analysis tool can also reveal this.

Driver Version: 9.4.1211

Java Version: 11

OS Version: Windows 10

PostgreSQL Version:9.6

To Reproduce Steps to reproduce the behaviour:

Assuming the following stored function exists on the database:

CREATE OR REPLACE FUNCTION GetCostCenters() RETURNS REFCURSOR AS $$ 
				DECLARE  
					cl1 REFCURSOR; 
				BEGIN 
					OPEN cl1 FOR
                                        -- any select returning 20 rows for example
					select CostCenterName, CostCenterNo from CostCenter; 
				      RETURN cl1; 
				END; 
				$$ LANGUAGE plpgsql;

See the following code snippet, nothing is closed to keep things simple:

	        Connection conn = ....; // get a Connection
		CallableStatement cs = conn.prepareCall("{? = call getCostCenters()}");
		cs.registerOutParameter(1, Types.REF_CURSOR);
		cs.setFetchSize(10);
		cs.execute();
		ResultSet rs = (ResultSet) cs.getObject(1);
		System.out.println("RS fetch size: " + rs.getFetchSize() + ", should be " + cs.getFetchSize());
		
		System.out.println("Checking what is already loaded in the RS ...");
                // using Spring Framework ReflectionTestUtils to peek into the rows member of the PgResultSet
		List<byte[][]> rows = (List<byte[][]>) ReflectionTestUtils.getField(rs, "rows");
		System.out.println(rows.size() + " records already loaded.");

Expected behaviour: The fetch size set on the CallableStatement should be used when processing the resultset resulted from the CallableStatement.