Oracle After Delete Trigger… How to avoid Mutating Table (ORA-04091)?

Question

Let\'s say we have the following table structures:

documents      docmentStatusHistory      status
+---------+   +--------------------+    +----------+
| doc         


        

Answer 1

The standard workaround to a mutating table error is to create

• A package with a collection of keys (i.e. docId's in this case). A temporary table would also work
• A before statement trigger that initializes the collection
• A row-level trigger that populates the collection with each docId that has changed
• An after statement trigger that iterates over the collection and does the actual UPDATE

So something like

CREATE OR REPLACE PACKAGE pkg_document_status
AS
  TYPE typ_changed_docids IS TABLE OF documentos.docId%type;
  changed_docids typ_changed_docids := new typ_changed_docids ();

  <<other methods>>
END;

CREATE OR REPLACE TRIGGER trg_init_collection
  BEFORE DELETE ON documentStatusHistory
BEGIN
  pkg_document_status.changed_docids.delete();
END;

CREATE OR REPLACE TRIGGER trg_populate_collection
  BEFORE DELETE ON documentStatusHistory
  FOR EACH ROW
BEGIN
  pkg_document_status.changed_docids.extend();
  pkg_document_status.changed_docids( pkg_document_status.changed_docids.count() ) := :old.docId;
END;

CREATE OR REPLACE TRIGGER trg_use_collection
  AFTER DELETE ON documentStatusHistory
BEGIN
  FOR i IN 1 .. pkg_document_status.changed_docids.count()
  LOOP
    <<fix the current status for pkg_document_status.changed_docids(i) >>
  END LOOP;
  pkg_document_status.changed_docids.delete();
END;

Answer 2

seems to be a duplicate of this question

check out Tom Kyte's take on that