Remove the limit on the number of entries allowed in catcaches, and

remove the infrastructure needed to enforce the limit, ie, the global
LRU list of cache entries.  On small-to-middling databases this wins
because maintaining the LRU list is a waste of time.  On large databases
this wins because it's better to keep more cache entries (we assume
such users can afford to use some more per-backend memory than was
contemplated in the Berkeley-era catcache design).  This provides a
noticeable improvement in the speed of psql \d on a 10000-table
database, though it doesn't make it instantaneous.

While at it, use per-catcache settings for the number of hash buckets
per catcache, rather than the former one-size-fits-all value.  It's a
bit silly to be using the same number of hash buckets for, eg, pg_am
and pg_attribute.  The specific values I used might need some tuning,
but they seem to be in the right ballpark based on CATCACHE_STATS
results from the standard regression tests.

src/include/utils/catcache.h

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/catcache.h,v 1.58 2006/03/05 15:59:07 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/catcache.h,v 1.59 2006/06/15 02:08:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -60,7 +60,6 @@ typedef struct catcache
 	 * searches, each of which will result in loading a negative entry
 	 */
 	long		cc_invals;		/* # of entries invalidated from cache */
-	long		cc_discards;	/* # of entries discarded due to overflow */
 	long		cc_lsearches;	/* total # list-searches */
 	long		cc_lhits;		/* # of matches against existing lists */
 #endif
@@ -75,11 +74,10 @@ typedef struct catctup
 	CatCache   *my_cache;		/* link to owning catcache */
 
 	/*
-	 * Each tuple in a cache is a member of two Dllists: one lists all the
-	 * elements in all the caches in LRU order, and the other lists just the
-	 * elements in one hashbucket of one cache, also in LRU order.
+	 * Each tuple in a cache is a member of a Dllist that stores the elements
+	 * of its hash bucket.  We keep each Dllist in LRU order to speed repeated
+	 * lookups.
 	 */
-	Dlelem		lrulist_elem;	/* list member of global LRU list */
 	Dlelem		cache_elem;		/* list member of per-bucket list */
 
 	/*
@@ -125,9 +123,8 @@ typedef struct catclist
 	 * table rows satisfying the partial key.  (Note: none of these will be
 	 * negative cache entries.)
 	 *
-	 * A CatCList is only a member of a per-cache list; we do not do separate
-	 * LRU management for CatCLists.  See CatalogCacheCleanup() for the
-	 * details of the management algorithm.
+	 * A CatCList is only a member of a per-cache list; we do not currently
+	 * divide them into hash buckets.
 	 *
 	 * A list marked "dead" must not be returned by subsequent searches.
 	 * However, it won't be physically deleted from the cache until its
@@ -143,7 +140,6 @@ typedef struct catclist
 	int			refcount;		/* number of active references */
 	bool		dead;			/* dead but not yet removed? */
 	bool		ordered;		/* members listed in index order? */
-	bool		touched;		/* used since last CatalogCacheCleanup? */
 	short		nkeys;			/* number of lookup keys specified */
 	uint32		hash_value;		/* hash value for lookup keys */
 	HeapTupleData tuple;		/* header for tuple holding keys */
@@ -156,8 +152,6 @@ typedef struct catcacheheader
 {
 	CatCache   *ch_caches;		/* head of list of CatCache structs */
 	int			ch_ntup;		/* # of tuples in all caches */
-	int			ch_maxtup;		/* max # of tuples allowed (LRU) */
-	Dllist		ch_lrulist;		/* overall LRU list, most recent first */
 } CatCacheHeader;
 
 
@@ -169,7 +163,8 @@ extern void AtEOXact_CatCache(bool isCommit);
 
 extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
 			 int reloidattr,
-			 int nkeys, const int *key);
+			 int nkeys, const int *key,
+			 int nbuckets);
 extern void InitCatCachePhase2(CatCache *cache);
 
 extern HeapTuple SearchCatCache(CatCache *cache,