Package org.postgresql.pljava.example.annotation

Class ThreadTest

  • All Implemented Interfaces:
    Runnable
    @SQLAction(implementor="notFromDDR",
           requires="strictlyNestedTest fn",
           install="select strictlyNestedTest()")
public class ThreadTest
extends Object
implements Runnable
    Test control of access to 1-thread backend by n-thread JVM. The "select strictlyNestedTest()" is marked "notFromDDR" because it actually does deadlock when invoked from within install_jar, though it succeeds when invoked directly. The explanation may lie in the JNI spec's caveat that JNI MonitorEnter/MonitorExit functions must be paired with each other and not arbitrarily mixed with JVM monitorenter/monitorexit bytecodes. In the present design, that can happen (install_jar uses a synchronized block to call into the backend when executing DDR commands; DDR command calling strictlyNestedTest leads to JNI MonitorExit in BEGIN_CALL; perhaps that does not effectively release the lock taken by the synchronized block).

    • Method Detail

      • strictlyNestedTest

        @Function(provides="strictlyNestedTest fn")
public static String strictlyNestedTest()
                                 throws SQLException
        Test that another thread can enter SPI while the calling thread is out. Create a thread that uses SPI to perform a query and set the value of result. Start and wait for that thread (so this one is clearly out of the backend the whole time), then return the result.
        Throws:
        SQLException