Question

I have a calculation in my DB need to update “field1” for “table1” after the update trigger.

The problem that updating that field will cause the after update trigger to fire and execute a lengthy procedure and display errors.

please advise how to update the “field1” after the “After update” trigger has been executed and without making the “after update” trigger to execute again.

I know that I can not use NEW with After trigger.

Thanks

Answer 1

One can use a custom locking mechanism based on context variables which prevent from repeating invocation of AFTER UPDATE trigger.

CREATE TRIGGER au FOR table
  AFTER UPDATE
  POSITION 0
AS
BEGIN
  IF RDB$GET_CONTEXT('USER_TRANSACTION', 'MY_LOCK') IS NULL THEN
  BEGIN
    RDB$SET_CONTEXT('USER_TRANSACTION', 'MY_LOCK', 1);

    ...
    Do your update operations here
    ...

    RDB$SET_CONTEXT('USER_TRANSACTION', 'MY_LOCK', NULL);
  END

  WHEN ANY DO
  BEGIN
    RDB$SET_CONTEXT('USER_TRANSACTION', 'MY_LOCK', NULL);
    EXCEPTION;
  END
END