Change SearchSysCache coding conventions so that a reference count is

maintained for each cache entry.  A cache entry will not be freed until
the matching ReleaseSysCache call has been executed.  This eliminates
worries about cache entries getting dropped while still in use.  See
my posting to pg-hackers of even date for more info.

1 files changed, 27 insertions, 15 deletions

diff --git a/src/include/lib/dllist.h b/src/include/lib/dllist.h
index 9e357a7fd76..9306d4e6b67 100644
--- a/src/include/lib/dllist.h
+++ b/src/include/lib/dllist.h
@@ -2,12 +2,11 @@
  *
  * dllist.h
  *		simple doubly linked list primitives
- *		the elements of the list are void* so the lists can contain
- *		anything
+ *		the elements of the list are void* so the lists can contain anything
  *		Dlelem can only be in one list at a time
  *
  *
- *	 Here's a small example of how to use Dllist's :
+ *	 Here's a small example of how to use Dllists:
  *
  *	 Dllist *lst;
  *	 Dlelem *elt;
@@ -24,10 +23,18 @@
  *	 DLFreeElem(elt);				   -- free the element since we don't
  *										  use it anymore
  *
+ *
+ * It is also possible to use Dllist objects that are embedded in larger
+ * structures instead of being separately malloc'd.  To do this, use
+ * DLInitElem() to initialize a Dllist field within a larger object.
+ * Don't forget to DLRemove() each field from its list (if any) before
+ * freeing the larger object!
+ *
+ *
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: dllist.h,v 1.13 2000/06/08 22:37:46 momjian Exp $
+ * $Id: dllist.h,v 1.14 2000/11/16 22:30:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -35,7 +42,6 @@
 #ifndef DLLIST_H
 #define DLLIST_H
 
-
 struct Dllist;
 struct Dlelem;
 
@@ -53,21 +59,27 @@ typedef struct Dllist
 	Dlelem	   *dll_tail;
 } Dllist;
 
-extern Dllist *DLNewList(void); /* initialize a new list */
-extern void DLFreeList(Dllist *);		/* free up a list and all the
+extern Dllist *DLNewList(void); /* allocate and initialize a list header */
+extern void DLInitList(Dllist *list);	/* init a header alloced by caller */
+extern void DLFreeList(Dllist *list);	/* free up a list and all the
 										 * nodes in it */
 extern Dlelem *DLNewElem(void *val);
-extern void DLFreeElem(Dlelem *);
-extern Dlelem *DLGetHead(Dllist *);
-extern Dlelem *DLGetTail(Dllist *);
-extern Dlelem *DLRemTail(Dllist *l);
-extern Dlelem *DLGetSucc(Dlelem *);		/* get successor */
-extern void DLRemove(Dlelem *); /* removes node from list */
+extern void DLInitElem(Dlelem *e, void *val);
+extern void DLFreeElem(Dlelem *e);
+extern void DLRemove(Dlelem *e);		/* removes node from list */
 extern void DLAddHead(Dllist *list, Dlelem *node);
 extern void DLAddTail(Dllist *list, Dlelem *node);
 extern Dlelem *DLRemHead(Dllist *list); /* remove and return the head */
-extern void DLMoveToFront(Dlelem *);	/* move node to front of its list */
+extern Dlelem *DLRemTail(Dllist *list);
+extern void DLMoveToFront(Dlelem *e);	/* move node to front of its list */
+
+/* These are macros for speed */
+#define DLGetHead(list)  ((list)->dll_head)
+#define DLGetTail(list)  ((list)->dll_tail)
+#define DLGetSucc(elem)  ((elem)->dle_next)
+#define DLGetPred(elem)  ((elem)->dle_prev)
+#define DLGetListHdr(elem)  ((elem)->dle_list)
 
-#define DLE_VAL(x)	(x->dle_val)
+#define DLE_VAL(elem)	((elem)->dle_val)
 
 #endif	 /* DLLIST_H */