JDBC driver: Closing a Connection does not close its Statement(s), potentially leading to exceptions related to memory leaks #932
Description
Describe the bug, including details regarding any error messages, version, and platform.
According to the JDBC specification 4.3 available at https://download.oracle.com/otn-pub/jcp/jdbc-4_3-mrel3-eval-spec/jdbc4.3-fr-spec.pdf, chapter 9.6.4.1:
All Statement objects created from a given
Connection object will be closed when the close method for the Connection
object is called.
In the Flight SQL JDBC driver closing a Connection does not automatically close the Statement instances obtained via that Connection, making it non compliant with the standard.
Due to this non compliance, on closing a Connection that has a Statement with one or more ResultSet that haven't been fully consumed, we get an exception on Connection.close()
Code to reproduce:
`
try {
// Establish connection
Connection connection = DriverManager.getConnection(jdbcUrl, properties);
System.out.println("Connected to Arrow Flight SQL server");
Statement stmt = connection.createStatement();
// my_table needs to have some rows for the bug to manifest itself
ResultSet rs = stmt.executeQuery("SELECT * FROM my_table");
// adding this close will eliminate the memory leak, without needing to close the Statement
// rs.close();
// with stmt.close() we get no memory leak, even if we didn't close the ResultSet
//stmt.close();
connection.close();
System.out.println("\nConnection closed");
} catch (Exception e) {
System.err.println("Error: " + e.getMessage());
e.printStackTrace();
}
`
Resulting in the following exception and stack trace
Dec 14, 2025 5:36:23 PM org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.memory.BaseAllocator close
SEVERE: Memory was leaked by query. Memory leaked: (32)
Allocator(flight-client) 0/32/32/9223372036854775807 (res/actual/peak/limit)
Error: Failed to clean up client resources.
java.sql.SQLException: Failed to clean up client resources.
at org.apache.arrow.driver.jdbc.client.ArrowFlightSqlClientHandler.close(ArrowFlightSqlClientHandler.java:269)
at org.apache.arrow.driver.jdbc.ArrowFlightConnection.close(ArrowFlightConnection.java:178)
at MemoryLeak.main(MemoryLeak.java:136)
Caused by: java.lang.IllegalStateException: Memory was leaked by query. Memory leaked: (32)
Allocator(flight-client) 0/32/32/9223372036854775807 (res/actual/peak/limit)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.memory.BaseAllocator.close(BaseAllocator.java:504)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.flight.FlightClient.close(FlightClient.java:744)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.util.AutoCloseables.close(AutoCloseables.java:97)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.util.AutoCloseables.close(AutoCloseables.java:75)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.flight.sql.FlightSqlClient.close(FlightSqlClient.java:1137)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.util.AutoCloseables.close(AutoCloseables.java:97)
at org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.util.AutoCloseables.close(AutoCloseables.java:75)
at org.apache.arrow.driver.jdbc.client.ArrowFlightSqlClientHandler.close(ArrowFlightSqlClientHandler.java:267)
... 2 more
While a user of the driver with good defensive programming practice would open the ResultSet and/or Statement in a try-with block, the driver should still follow the standard and not produce this Exception.
I believe this bug has been here since the creation of the driver, but I have confirmed that it occurs for both version 17.0.0 and 18.3.0 of the driver.