Add some notes about memory management of RI plans.

diff --git a/src/backend/utils/adt/ri_triggers.c b/src/backend/utils/adt/ri_triggers.c
index 77d5c79feafc6964c44d1cd63b62b70c238dd8eb..94d9b7313a14f2a7f4d19fe15738c1aaffa9b66c 100644 (file)
--- a/src/backend/utils/adt/ri_triggers.c
+++ b/src/backend/utils/adt/ri_triggers.c
@@ -4,9 +4,21 @@
  *     Generic trigger procedures for referential integrity constraint
  *     checks.
  *
- *     1999 Jan Wieck
+ *     Note about memory management: the private hashtables kept here live
+ *     across query and transaction boundaries, in fact they live as long as
+ *     the backend does.  This works because the hashtable structures
+ *     themselves are allocated by dynahash.c in its permanent DynaHashCxt,
+ *     and the parse/plan node trees they point to are copied into
+ *     TopMemoryContext using SPI_saveplan().  This is pretty ugly, since there
+ *     is no way to free a no-longer-needed plan tree, but then again we don't
+ *     yet have any bookkeeping that would allow us to detect that a plan isn't
+ *     needed anymore.  Improve it someday.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.20 2000/12/22 18:35:09 tgl Exp $
+ *
+ * Portions Copyright (c) 2000-2001, PostgreSQL Global Development Group
+ * Copyright 1999 Jan Wieck
+ *
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.21 2001/02/15 21:57:43 tgl Exp $
  *
  * ----------
  */