Add the usage count statistics to the information available in

contrib/pgbuffercache.

Greg Smith

contrib/pg_buffercache/README.pg_buffercache

@@ -40,7 +40,7 @@ Notes
    reldatabase    | pg_database.oid      | Database for the relation.
    relblocknumber |                      | Offset of the page in the relation.
    isdirty        |                      | Is the page dirty?
-
+   usagecount     |                      | Page LRU count
 
   There is one row for each buffer in the shared cache. Unused buffers are
   shown with all fields null except bufferid.
@@ -61,19 +61,21 @@ Sample output
   regression=# \d pg_buffercache;
        View "public.pg_buffercache"
        Column     |  Type    | Modifiers
-  ----------------+---------+-----------
+  ----------------+----------+-----------
    bufferid       | integer  |
    relfilenode    | oid      |
    reltablespace  | oid      |
    reldatabase    | oid      |
    relblocknumber | bigint   |
    isdirty        | boolean  |
+   usagecount     | smallint |
+
   View definition:
    SELECT p.bufferid, p.relfilenode, p.reltablespace, p.reldatabase, 
-          p.relblocknumber, p.isdirty
+          p.relblocknumber, p.isdirty, p.usagecount
      FROM pg_buffercache_pages() p(bufferid integer, relfilenode oid, 
      reltablespace oid, reldatabase oid, relblocknumber bigint, 
-     isdirty boolean);
+     isdirty boolean, usagecount smallint);
 
   regression=# SELECT c.relname, count(*) AS buffers
                FROM pg_class c INNER JOIN pg_buffercache b

contrib/pg_buffercache/pg_buffercache.sql.in

@@ -12,7 +12,7 @@ LANGUAGE C;
 CREATE VIEW pg_buffercache AS
 	SELECT P.* FROM pg_buffercache_pages() AS P
  	(bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid, 
- 	 relblocknumber int8, isdirty bool);
+ 	 relblocknumber int8, isdirty bool, usagecount int2);
  
 -- Don't want these to be available at public.
 REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;

contrib/pg_buffercache/pg_buffercache_pages.c

@@ -3,7 +3,7 @@
  * pg_buffercache_pages.c
  *	  display some contents of the buffer cache
  *
- *	  $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.11 2006/10/22 17:49:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.12 2007/04/07 16:09:14 momjian Exp $
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -16,7 +16,7 @@
 #include "utils/relcache.h"
 
 
-#define NUM_BUFFERCACHE_PAGES_ELEM	6
+#define NUM_BUFFERCACHE_PAGES_ELEM	7
 
 PG_MODULE_MAGIC;
 
@@ -35,6 +35,7 @@ typedef struct
 	BlockNumber blocknum;
 	bool		isvalid;
 	bool		isdirty;
+	uint16		usagecount;
 }	BufferCachePagesRec;
 
 
@@ -91,6 +92,8 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 						   INT8OID, -1, 0);
 		TupleDescInitEntry(tupledesc, (AttrNumber) 6, "isdirty",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupledesc, (AttrNumber) 7, "usage_count",
+						   INT2OID, -1, 0);
 
 		fctx->tupdesc = BlessTupleDesc(tupledesc);
 
@@ -126,6 +129,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			fctx->record[i].reltablespace = bufHdr->tag.rnode.spcNode;
 			fctx->record[i].reldatabase = bufHdr->tag.rnode.dbNode;
 			fctx->record[i].blocknum = bufHdr->tag.blockNum;
+			fctx->record[i].usagecount = bufHdr->usage_count;
 
 			if (bufHdr->flags & BM_DIRTY)
 				fctx->record[i].isdirty = true;
@@ -172,6 +176,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			nulls[3] = true;
 			nulls[4] = true;
 			nulls[5] = true;
+			nulls[6] = true;
 		}
 		else
 		{
@@ -185,6 +190,8 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			nulls[4] = false;
 			values[5] = BoolGetDatum(fctx->record[i].isdirty);
 			nulls[5] = false;
+			values[6] = Int16GetDatum(fctx->record[i].usagecount);
+			nulls[6] = false;
 		}
 
 		/* Build and return the tuple. */