Reimplement the linked list data structure used throughout the backend.

In the past, we used a 'Lispy' linked list implementation: a "list" was
merely a pointer to the head node of the list. The problem with that
design is that it makes lappend() and length() linear time. This patch
fixes that problem (and others) by maintaining a count of the list
length and a pointer to the tail node along with each head node pointer.
A "list" is now a pointer to a structure containing some meta-data
about the list; the head and tail pointers in that structure refer
to ListCell structures that maintain the actual linked list of nodes.

The function names of the list API have also been changed to, I hope,
be more logically consistent. By default, the old function names are
still available; they will be disabled-by-default once the rest of
the tree has been updated to use the new API names.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c
index 5732e5ab424..5e91a7283ec 100644
--- a/src/backend/utils/cache/catcache.c
+++ b/src/backend/utils/cache/catcache.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/catcache.c,v 1.111 2003/11/29 19:52:00 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/catcache.c,v 1.112 2004/05/26 04:41:40 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1317,6 +1317,7 @@ SearchCatCacheList(CatCache *cache,
 	CatCList   *cl;
 	CatCTup    *ct;
 	List	   *ctlist;
+	ListCell   *ctlist_item;
 	int			nmembers;
 	Relation	relation;
 	SysScanDesc scandesc;
@@ -1510,15 +1511,16 @@ SearchCatCacheList(CatCache *cache,
 	cl->hash_value = lHashValue;
 	cl->n_members = nmembers;
 	/* The list is backwards because we built it with lcons */
+	ctlist_item = list_head(ctlist);
 	for (i = nmembers; --i >= 0;)
 	{
-		cl->members[i] = ct = (CatCTup *) lfirst(ctlist);
+		cl->members[i] = ct = (CatCTup *) lfirst(ctlist_item);
 		Assert(ct->c_list == NULL);
 		ct->c_list = cl;
 		/* mark list dead if any members already dead */
 		if (ct->dead)
 			cl->dead = true;
-		ctlist = lnext(ctlist);
+		ctlist_item = lnext(ctlist_item);
 	}
 
 	DLAddHead(&cache->cc_lists, &cl->cache_elem);