Mark Kirkwood wrote:
> Mark Kirkwood wrote:
>
>>
>> I couldn't use int4 as the underlying datatype is unsigned int (not
>> available as exposed Pg type). However, using int8 sounds promising
>> (is int8 larger than unsigned int on 64-bit platforms?).
>
>
> Blocknumber is defined as uint32 in block.h - so should always be safe
> to represent as an int8 I am thinking.
>
> I will look at patching pg_buffercache, changing numeric -> int8 for the
> relblocknumber column. This seems a tidier solution than using numeric,
> and loses the numeric overhead.

This patch changes the use of numeric to int8 to represent the
relblocknumber column.

regards

Mark


diff -Ncar pgsql.orig/contrib/pg_buffercache/README.pg_buffercache pgsql/contrib/pg_buffercache/README.pg_buffercache
*** pgsql.orig/contrib/pg_buffercache/README.pg_buffercache Tue May 31 11:02:41 2005
--- pgsql/contrib/pg_buffercache/README.pg_buffercache Tue May 31 11:05:48 2005
***************
*** 66,78 ****
relfilenode | oid |
reltablespace | oid |
reldatabase | oid |
! relblocknumber | numeric |
isdirty | boolean |
View definition:
SELECT p.bufferid, p.relfilenode, p.reltablespace, p.reldatabase,
p.relblocknumber, p.isdirty
FROM pg_buffercache_pages() p(bufferid integer, relfilenode oid,
! reltablespace oid, reldatabase oid, relblocknumber numeric(10,0),
isdirty boolean);

regression=# SELECT c.relname, count(*) AS buffers
--- 66,78 ----
relfilenode | oid |
reltablespace | oid |
reldatabase | oid |
! relblocknumber | bigint |
isdirty | boolean |
View definition:
SELECT p.bufferid, p.relfilenode, p.reltablespace, p.reldatabase,
p.relblocknumber, p.isdirty
FROM pg_buffercache_pages() p(bufferid integer, relfilenode oid,
! reltablespace oid, reldatabase oid, relblocknumber bigint,
isdirty boolean);

regression=# SELECT c.relname, count(*) AS buffers
diff -Ncar pgsql.orig/contrib/pg_buffercache/pg_buffercache.sql.in pgsql/contrib/pg_buffercache/pg_buffercache.sql.in
*** pgsql.orig/contrib/pg_buffercache/pg_buffercache.sql.in Tue May 31 11:02:41 2005
--- pgsql/contrib/pg_buffercache/pg_buffercache.sql.in Tue May 31 09:15:03 2005
***************
*** 11,17 ****
CREATE VIEW pg_buffercache AS
SELECT P.* FROM pg_buffercache_pages() AS P
(bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid,
! relblocknumber numeric(10), isdirty bool);

-- Don't want these to be available at public.
REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
--- 11,17 ----
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);

-- Don't want these to be available at public.
REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
diff -Ncar pgsql.orig/contrib/pg_buffercache/pg_buffercache_pages.c pgsql/contrib/pg_buffercache/pg_buffercache_pages.c
*** pgsql.orig/contrib/pg_buffercache/pg_buffercache_pages.c Tue May 31 11:02:41 2005
--- pgsql/contrib/pg_buffercache/pg_buffercache_pages.c Tue May 31 11:23:46 2005
***************
*** 93,99 ****
TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
OIDOID, -1, 0);
TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblockbumber",
! NUMERICOID, -1, 0);
TupleDescInitEntry(tupledesc, (AttrNumber) 6, "isdirty",
BOOLOID, -1, 0);

--- 93,99 ----
TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
OIDOID, -1, 0);
TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblockbumber",
! INT8OID, -1, 0);
TupleDescInitEntry(tupledesc, (AttrNumber) 6, "isdirty",
BOOLOID, -1, 0);




---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

Mark Kirkwood <markir@paradise.net.nz> writes:
> This patch changes the use of numeric to int8 to represent the
> relblocknumber column.

Applied, thanks.

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddressHere" to majordomo@postgresql.org)

Tom Lane wrote:
> Mark Kirkwood <markir@paradise.net.nz> writes:
>
>>This patch changes the use of numeric to int8 to represent the
>>relblocknumber column.
>
>
> Applied, thanks.
>
>

This reminds me:

I did some patches for 7.4 and 8.0 a while ago (attached) - while I do
not expect these to be applied (unless it's ok for contrib to get extra
modules in stable releases...), is there somewhere for things like this
to go?

cheers

Mark

P.s : They are amended to use int8 too :-)

diff -Naur pgsql-7.4.7.orig/contrib/Makefile pgsql-7.4.7/contrib/Makefile
--- pgsql-7.4.7.orig/contrib/Makefile Fri Mar 18 11:44:25 2005
+++ pgsql-7.4.7/contrib/Makefile Fri Mar 18 10:55:55 2005
@@ -25,6 +25,7 @@
noupdate \
oid2name \
pg_autovacuum \
+ pg_buffercache \
pg_dumplo \
pg_logger \
pgbench \
diff -Naur pgsql-7.4.7.orig/contrib/README pgsql-7.4.7/contrib/README
--- pgsql-7.4.7.orig/contrib/README Fri Mar 18 11:44:19 2005
+++ pgsql-7.4.7/contrib/README Fri Mar 18 10:55:55 2005
@@ -136,6 +136,10 @@
Automatically performs vacuum
by Matthew T. O'Connor <matthew@zeut.net>

+pg_buffercache -
+ Real-time queries on the shared buffer cache
+ by Mark Kirkwood <markir@paradise.net.nz>
+
pg_dumplo -
Dump large objects
by Karel Zak <zakkr@zf.jcu.cz>
diff -Naur pgsql-7.4.7.orig/contrib/pg_buffercache/Makefile pgsql-7.4.7/contrib/pg_buffercache/Makefile
--- pgsql-7.4.7.orig/contrib/pg_buffercache/Makefile Thu Jan 1 12:00:00 1970
+++ pgsql-7.4.7/contrib/pg_buffercache/Makefile Fri Mar 18 10:55:55 2005
@@ -0,0 +1,17 @@
+# $PostgreSQL: pgsql/contrib/pg_buffercache/Makefile,v 1.1 2005/03/12 15:36:24 neilc Exp $
+
+MODULE_big = pg_buffercache
+OBJS = pg_buffercache_pages.o
+
+DATA_built = pg_buffercache.sql
+DOCS = README.pg_buffercache
+
+ifdef USE_PGXS
+PGXS = $(shell pg_config --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_buffercache
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff -Naur pgsql-7.4.7.orig/contrib/pg_buffercache/README.pg_buffercache pgsql-7.4.7/contrib/pg_buffercache/README.pg_buffercache
--- pgsql-7.4.7.orig/contrib/pg_buffercache/README.pg_buffercache Thu Jan 1 12:00:00 1970
+++ pgsql-7.4.7/contrib/pg_buffercache/README.pg_buffercache Fri Mar 18 11:47:28 2005
@@ -0,0 +1,110 @@
+Pg_buffercache - Real time queries on the shared buffer cache.
+--------------
+
+ This module consists of a C function 'pg_buffercache_pages()' that returns
+ a set of records, plus a view 'pg_buffercache' to wrapper the function.
+
+ The intent is to do for the buffercache what pg_locks does for locks, i.e -
+ ability to examine what is happening at any given time without having to
+ restart or rebuild the server with debugging code added.
+
+ By default public access is REVOKED from both of these, just in case there
+ are security issues lurking.
+
+
+Installation
+------------
+
+ Build and install the main Postgresql source, then this contrib module:
+
+ $ cd contrib/pg_buffercache
+ $ gmake
+ $ gmake install
+
+
+ To register the functions:
+
+ $ psql -d <database> -f pg_buffercache.sql
+
+
+Notes
+-----
+
+ The definition of the columns exposed in the view is:
+
+ Column | references | Description
+ ----------------+----------------------+------------------------------------
+ bufferid | | Id, 1->shared_buffers.
+ relfilenode | pg_class.relfilenode | Refilenode of the relation.
+ reldatabase | pg_database.oid | Database for the relation.
+ relblocknumber | | Offset of the page in the relation.
+ isdirty | | Is the page dirty?
+
+
+ There is one row for each buffer in the shared cache. Unused buffers are
+ shown with all fields null except bufferid.
+
+ Because the cache is shared by all the databases, there are pages from
+ relations not belonging to the current database.
+
+ When the pg_buffercache view is accessed, internal buffer manager locks are
+ taken, and a copy of the buffer cache data is made for the view to display.
+ This ensures that the view produces a consistent set of results, while not
+ blocking normal buffer activity longer than necessary. Nonetheless there
+ could be some impact on database performance if this view is read often.
+
+
+Sample output
+-------------
+
+ regression=# \d pg_buffercache;
+ View "public.pg_buffercache"
+ Column | Type | Modifiers
+ ----------------+---------+-----------
+ bufferid | integer |
+ relfilenode | oid |
+ reldatabase | oid |
+ relblocknumber | bigint |
+ isdirty | boolean |
+ View definition:
+ SELECT p.bufferid, p.relfilenode, p.reldatabase,
+ p.relblocknumber, p.isdirty
+ FROM pg_buffercache_pages() p(bufferid integer, relfilenode oid,
+ reltablespace oid, reldatabase oid, relblocknumber bigint,
+ isdirty boolean);
+
+ regression=# SELECT c.relname, count(*) AS buffers
+ FROM pg_class c, pg_buffercache b
+ WHERE b.relfilenode = c.relfilenode
+ GROUP BY c.relname
+ ORDER BY 2 DESC LIMIT 10;
+ relname | buffers
+ ---------------------------------+---------
+ tenk2 | 345
+ tenk1 | 141
+ pg_proc | 46
+ pg_class | 45
+ pg_attribute | 43
+ pg_class_relname_nsp_index | 30
+ pg_proc_proname_args_nsp_index | 28
+ pg_attribute_relid_attnam_index | 26
+ pg_depend | 22
+ pg_depend_reference_index | 20
+ (10 rows)
+
+ regression=#
+
+
+Author
+------
+
+ * Mark Kirkwood <markir@paradise.net.nz>
+
+
+Help
+----
+
+ * Design suggestions : Neil Conway <neilc@samurai.com>
+ * Debugging advice : Tom Lane <tgl@sss.pgh.pa.us>
+
+ Thanks guys!
diff -Naur pgsql-7.4.7.orig/contrib/pg_buffercache/pg_buffercache.sql.in pgsql-7.4.7/contrib/pg_buffercache/pg_buffercache.sql.in
--- pgsql-7.4.7.orig/contrib/pg_buffercache/pg_buffercache.sql.in Thu Jan 1 12:00:00 1970
+++ pgsql-7.4.7/contrib/pg_buffercache/pg_buffercache.sql.in Fri Mar 18 11:10:16 2005
@@ -0,0 +1,18 @@
+-- Adjust this setting to control where the objects get created.
+SET search_path = public;
+
+-- Register the function.
+CREATE OR REPLACE FUNCTION pg_buffercache_pages()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'pg_buffercache_pages'
+LANGUAGE 'C';
+
+-- Create a view for convenient access.
+CREATE VIEW pg_buffercache AS
+ SELECT P.* FROM pg_buffercache_pages() AS P
+ (bufferid integer, relfilenode oid, reldatabase oid,
+ relblocknumber int8, isdirty bool);
+
+-- Don't want these to be available at public.
+REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
+REVOKE ALL ON pg_buffercache FROM PUBLIC;
diff -Naur pgsql-7.4.7.orig/contrib/pg_buffercache/pg_buffercache_pages.c pgsql-7.4.7/contrib/pg_buffercache/pg_buffercache_pages.c
--- pgsql-7.4.7.orig/contrib/pg_buffercache/pg_buffercache_pages.c Thu Jan 1 12:00:00 1970
+++ pgsql-7.4.7/contrib/pg_buffercache/pg_buffercache_pages.c Fri Mar 18 11:37:26 2005
@@ -0,0 +1,234 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_buffercache_pages.c
+ * display some contents of the buffer cache
+ *
+ * $PostgreSQL$
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+#include "funcapi.h"
+#include "catalog/pg_type.h"
+#include "storage/buf_internals.h"
+#include "storage/bufmgr.h"
+#include "utils/relcache.h"
+
+
+#define NUM_BUFFERCACHE_PAGES_ELEM 5
+
+
+extern Datum pg_buffercache_pages(PG_FUNCTION_ARGS);
+
+
+/*
+ * Record structure holding the to be exposed cache data.
+ */
+typedef struct
+{
+
+ uint32 bufferid;
+ Oid relfilenode;
+ Oid reldatabase;
+ BlockNumber blocknum;
+ bool isvalid;
+ bool isdirty;
+
+} BufferCachePagesRec;
+
+
+/*
+ * Function context for data persisting over repeated calls.
+ */
+typedef struct
+{
+
+ AttInMetadata *attinmeta;
+ TupleTableSlot *slot;
+ BufferCachePagesRec *record;
+ char *values[NUM_BUFFERCACHE_PAGES_ELEM];
+
+} BufferCachePagesContext;
+
+
+/*
+ * Function returning data from the shared buffer cache - buffer number,
+ * relation node/database/blocknum and dirty indicator.
+ */
+PG_FUNCTION_INFO_V1(pg_buffercache_pages);
+Datum
+pg_buffercache_pages(PG_FUNCTION_ARGS)
+{
+
+ FuncCallContext *funcctx;
+ Datum result;
+ MemoryContext oldcontext;
+ BufferCachePagesContext *fctx; /* User function context. */
+ TupleDesc tupledesc;
+ HeapTuple tuple;
+
+ if (SRF_IS_FIRSTCALL())
+ {
+ RelFileNode rnode;
+ uint32 i;
+ BufferDesc *bufHdr;
+
+
+ funcctx = SRF_FIRSTCALL_INIT();
+
+ /* Switch context when allocating stuff to be used in later calls */
+ oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+ /* Construct a tuple to return. */
+ tupledesc = CreateTemplateTupleDesc(NUM_BUFFERCACHE_PAGES_ELEM , false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 1, "bufferid",
+ INT4OID, -1, 0, false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
+ OIDOID, -1, 0, false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reldatabase",
+ OIDOID, -1, 0, false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 4, "relblockbumber",
+ INT8OID, -1, 0, false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 5, "isdirty",
+ BOOLOID, -1, 0, false);
+
+ /* Generate attribute metadata needed later to produce tuples */
+ funcctx->attinmeta = TupleDescGetAttInMetadata(tupledesc);
+
+ /* Allocate a slot for this tupledesc */
+ funcctx->slot = TupleDescGetSlot(tupledesc);
+
+ /*
+ * Create a function context for cross-call persistence
+ * and initialize the buffer counters.
+ */
+ fctx = (BufferCachePagesContext *) palloc(sizeof(BufferCachePagesContext));
+ funcctx->max_calls = NBuffers;
+ funcctx->user_fctx = fctx;
+
+
+ /* Allocate NBuffers worth of BufferCachePagesRec records. */
+ fctx->record = (BufferCachePagesRec *) palloc(sizeof(BufferCachePagesRec) * NBuffers);
+
+ /* allocate the strings for tuple formation */
+ fctx->values[0] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[1] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[2] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[3] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[4] = (char *) palloc(2);
+
+
+ /* Return to original context when allocating transient memory */
+ MemoryContextSwitchTo(oldcontext);
+
+
+ /*
+ * Lock Buffer manager and scan though all the buffers, saving the
+ * relevant fields in the fctx->record structure.
+ */
+ LWLockAcquire(BufMgrLock, LW_SHARED);
+
+ for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
+ {
+
+ rnode = bufHdr->tag.rnode;
+
+ fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
+ fctx->record[i].relfilenode = rnode.relNode;
+ fctx->record[i].reldatabase = rnode.tblNode;
+ fctx->record[i].blocknum = bufHdr->tag.blockNum;
+
+ if ( bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
+ {
+ fctx->record[i].isdirty = true;
+ }
+ else
+ {
+ fctx->record[i].isdirty = false;
+ }
+
+ /* Note if the buffer is valid */
+ if ( (bufHdr->flags & BM_VALID))
+ {
+ fctx->record[i].isvalid = true;
+ }
+ else
+ {
+ fctx->record[i].isvalid = false;
+ }
+
+
+ }
+
+ /* Release Buffer manager. */
+ LWLockRelease(BufMgrLock);
+ }
+
+ funcctx = SRF_PERCALL_SETUP();
+
+ /* Get the saved state */
+ fctx = funcctx->user_fctx;
+
+
+ if (funcctx->call_cntr < funcctx->max_calls)
+ {
+ uint32 i = funcctx->call_cntr;
+ char *values[NUM_BUFFERCACHE_PAGES_ELEM];
+ int j;
+
+ /*
+ * Use a temporary values array, initially pointing to
+ * fctx->values, so it can be reassigned w/o losing the storage
+ * for subsequent calls.
+ */
+ for (j = 0; j < NUM_BUFFERCACHE_PAGES_ELEM; j++)
+ {
+ values[j] = fctx->values[j];
+ }
+
+
+ /*
+ * Set all fields except the bufferid to null if the buffer is
+ * unused or not valid.
+ */
+ if (fctx->record[i].blocknum == InvalidBlockNumber ||
+ fctx->record[i].isvalid == false )
+ {
+
+ sprintf(values[0], "%u", fctx->record[i].bufferid);
+ values[1] = NULL;
+ values[2] = NULL;
+ values[3] = NULL;
+ values[4] = NULL;
+
+ }
+ else
+ {
+
+ sprintf(values[0], "%u", fctx->record[i].bufferid);
+ sprintf(values[1], "%u", fctx->record[i].relfilenode);
+ sprintf(values[2], "%u", fctx->record[i].reldatabase);
+ sprintf(values[3], "%u", fctx->record[i].blocknum);
+ if (fctx->record[i].isdirty)
+ {
+ strcpy(values[4], "t");
+ }
+ else
+ {
+ strcpy(values[4], "f");
+ }
+
+ }
+
+
+ /* Build and return the tuple. */
+ tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
+ result = TupleGetDatum(funcctx->slot, tuple);
+
+
+ SRF_RETURN_NEXT(funcctx, result);
+ }
+ else
+ SRF_RETURN_DONE(funcctx);
+
+}
+


diff -Naur pgsql-8.0.1.orig/contrib/Makefile pgsql-8.0.1/contrib/Makefile
--- pgsql-8.0.1.orig/contrib/Makefile Fri Mar 18 10:48:52 2005
+++ pgsql-8.0.1/contrib/Makefile Fri Mar 18 10:33:15 2005
@@ -26,6 +26,7 @@
noupdate \
oid2name \
pg_autovacuum \
+ pg_buffercache \
pg_dumplo \
pg_trgm \
pgbench \
diff -Naur pgsql-8.0.1.orig/contrib/README pgsql-8.0.1/contrib/README
--- pgsql-8.0.1.orig/contrib/README Fri Mar 18 10:48:46 2005
+++ pgsql-8.0.1/contrib/README Fri Mar 18 10:34:18 2005
@@ -136,6 +136,10 @@
Automatically performs vacuum
by Matthew T. O'Connor <matthew@zeut.net>

+pg_buffercache -
+ Real-time queries on the shared buffer cache
+ by Mark Kirkwood <markir@paradise.net.nz>
+
pg_dumplo -
Dump large objects
by Karel Zak <zakkr@zf.jcu.cz>
diff -Naur pgsql-8.0.1.orig/contrib/pg_buffercache/Makefile pgsql-8.0.1/contrib/pg_buffercache/Makefile
--- pgsql-8.0.1.orig/contrib/pg_buffercache/Makefile Thu Jan 1 12:00:00 1970
+++ pgsql-8.0.1/contrib/pg_buffercache/Makefile Fri Mar 18 09:59:34 2005
@@ -0,0 +1,17 @@
+# $PostgreSQL: pgsql/contrib/pg_buffercache/Makefile,v 1.1 2005/03/12 15:36:24 neilc Exp $
+
+MODULE_big = pg_buffercache
+OBJS = pg_buffercache_pages.o
+
+DATA_built = pg_buffercache.sql
+DOCS = README.pg_buffercache
+
+ifdef USE_PGXS
+PGXS = $(shell pg_config --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_buffercache
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff -Naur pgsql-8.0.1.orig/contrib/pg_buffercache/README.pg_buffercache pgsql-8.0.1/contrib/pg_buffercache/README.pg_buffercache
--- pgsql-8.0.1.orig/contrib/pg_buffercache/README.pg_buffercache Thu Jan 1 12:00:00 1970
+++ pgsql-8.0.1/contrib/pg_buffercache/README.pg_buffercache Fri Mar 18 09:59:34 2005
@@ -0,0 +1,112 @@
+Pg_buffercache - Real time queries on the shared buffer cache.
+--------------
+
+ This module consists of a C function 'pg_buffercache_pages()' that returns
+ a set of records, plus a view 'pg_buffercache' to wrapper the function.
+
+ The intent is to do for the buffercache what pg_locks does for locks, i.e -
+ ability to examine what is happening at any given time without having to
+ restart or rebuild the server with debugging code added.
+
+ By default public access is REVOKED from both of these, just in case there
+ are security issues lurking.
+
+
+Installation
+------------
+
+ Build and install the main Postgresql source, then this contrib module:
+
+ $ cd contrib/pg_buffercache
+ $ gmake
+ $ gmake install
+
+
+ To register the functions:
+
+ $ psql -d <database> -f pg_buffercache.sql
+
+
+Notes
+-----
+
+ The definition of the columns exposed in the view is:
+
+ Column | references | Description
+ ----------------+----------------------+------------------------------------
+ bufferid | | Id, 1->shared_buffers.
+ relfilenode | pg_class.relfilenode | Refilenode of the relation.
+ reltablespace | pg_tablespace.oid | Tablespace oid of the relation.
+ reldatabase | pg_database.oid | Database for the relation.
+ relblocknumber | | Offset of the page in the relation.
+ isdirty | | Is the page dirty?
+
+
+ There is one row for each buffer in the shared cache. Unused buffers are
+ shown with all fields null except bufferid.
+
+ Because the cache is shared by all the databases, there are pages from
+ relations not belonging to the current database.
+
+ When the pg_buffercache view is accessed, internal buffer manager locks are
+ taken, and a copy of the buffer cache data is made for the view to display.
+ This ensures that the view produces a consistent set of results, while not
+ blocking normal buffer activity longer than necessary. Nonetheless there
+ could be some impact on database performance if this view is read often.
+
+
+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 |
+ View definition:
+ SELECT p.bufferid, p.relfilenode, p.reltablespace, p.reldatabase,
+ p.relblocknumber, p.isdirty
+ FROM pg_buffercache_pages() p(bufferid integer, relfilenode oid,
+ reltablespace oid, reldatabase oid, relblocknumber bigint,
+ isdirty boolean);
+
+ regression=# SELECT c.relname, count(*) AS buffers
+ FROM pg_class c, pg_buffercache b
+ WHERE b.relfilenode = c.relfilenode
+ GROUP BY c.relname
+ ORDER BY 2 DESC LIMIT 10;
+ relname | buffers
+ ---------------------------------+---------
+ tenk2 | 345
+ tenk1 | 141
+ pg_proc | 46
+ pg_class | 45
+ pg_attribute | 43
+ pg_class_relname_nsp_index | 30
+ pg_proc_proname_args_nsp_index | 28
+ pg_attribute_relid_attnam_index | 26
+ pg_depend | 22
+ pg_depend_reference_index | 20
+ (10 rows)
+
+ regression=#
+
+
+Author
+------
+
+ * Mark Kirkwood <markir@paradise.net.nz>
+
+
+Help
+----
+
+ * Design suggestions : Neil Conway <neilc@samurai.com>
+ * Debugging advice : Tom Lane <tgl@sss.pgh.pa.us>
+
+ Thanks guys!
diff -Naur pgsql-8.0.1.orig/contrib/pg_buffercache/pg_buffercache.sql.in pgsql-8.0.1/contrib/pg_buffercache/pg_buffercache.sql.in
--- pgsql-8.0.1.orig/contrib/pg_buffercache/pg_buffercache.sql.in Thu Jan 1 12:00:00 1970
+++ pgsql-8.0.1/contrib/pg_buffercache/pg_buffercache.sql.in Fri Mar 18 09:59:34 2005
@@ -0,0 +1,18 @@
+-- Adjust this setting to control where the objects get created.
+SET search_path = public;
+
+-- Register the function.
+CREATE OR REPLACE FUNCTION pg_buffercache_pages()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'pg_buffercache_pages'
+LANGUAGE 'C';
+
+-- Create a view for convenient access.
+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);
+
+-- Don't want these to be available at public.
+REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
+REVOKE ALL ON pg_buffercache FROM PUBLIC;
diff -Naur pgsql-8.0.1.orig/contrib/pg_buffercache/pg_buffercache_pages.c pgsql-8.0.1/contrib/pg_buffercache/pg_buffercache_pages.c
--- pgsql-8.0.1.orig/contrib/pg_buffercache/pg_buffercache_pages.c Thu Jan 1 12:00:00 1970
+++ pgsql-8.0.1/contrib/pg_buffercache/pg_buffercache_pages.c Fri Mar 18 10:31:15 2005
@@ -0,0 +1,242 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_buffercache_pages.c
+ * display some contents of the buffer cache
+ *
+ * $PostgreSQL$
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+#include "funcapi.h"
+#include "catalog/pg_type.h"
+#include "storage/buf_internals.h"
+#include "storage/bufmgr.h"
+#include "utils/relcache.h"
+
+
+#define NUM_BUFFERCACHE_PAGES_ELEM 6
+
+extern Datum pg_buffercache_pages(PG_FUNCTION_ARGS);
+
+#if defined (WIN32) || defined (__CYGWIN__)
+extern DLLIMPORT BufferDesc *BufferDescriptors;
+extern DLLIMPORT volatile uint32 InterruptHoldoffCount;
+#endif
+
+
+
+/*
+ * Record structure holding the to be exposed cache data.
+ */
+typedef struct
+{
+
+ uint32 bufferid;
+ Oid relfilenode;
+ Oid reltablespace;
+ Oid reldatabase;
+ BlockNumber blocknum;
+ bool isvalid;
+ bool isdirty;
+
+} BufferCachePagesRec;
+
+
+/*
+ * Function context for data persisting over repeated calls.
+ */
+typedef struct
+{
+
+ AttInMetadata *attinmeta;
+ BufferCachePagesRec *record;
+ char *values[NUM_BUFFERCACHE_PAGES_ELEM];
+
+} BufferCachePagesContext;
+
+
+/*
+ * Function returning data from the shared buffer cache - buffer number,
+ * relation node/tablespace/database/blocknum and dirty indicator.
+ */
+PG_FUNCTION_INFO_V1(pg_buffercache_pages);
+Datum
+pg_buffercache_pages(PG_FUNCTION_ARGS)
+{
+
+ FuncCallContext *funcctx;
+ Datum result;
+ MemoryContext oldcontext;
+ BufferCachePagesContext *fctx; /* User function context. */
+ TupleDesc tupledesc;
+ HeapTuple tuple;
+
+ if (SRF_IS_FIRSTCALL())
+ {
+ RelFileNode rnode;
+ uint32 i;
+ BufferDesc *bufHdr;
+
+
+ funcctx = SRF_FIRSTCALL_INIT();
+
+ /* Switch context when allocating stuff to be used in later calls */
+ oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+ /* Construct a tuple to return. */
+ tupledesc = CreateTemplateTupleDesc(NUM_BUFFERCACHE_PAGES_ELEM , false);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 1, "bufferid",
+ INT4OID, -1, 0);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
+ OIDOID, -1, 0);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reltablespace",
+ OIDOID, -1, 0);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
+ OIDOID, -1, 0);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblockbumber",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupledesc, (AttrNumber) 6, "isdirty",
+ BOOLOID, -1, 0);
+
+ /* Generate attribute metadata needed later to produce tuples */
+ funcctx->attinmeta = TupleDescGetAttInMetadata(tupledesc);
+
+ /*
+ * Create a function context for cross-call persistence
+ * and initialize the buffer counters.
+ */
+ fctx = (BufferCachePagesContext *) palloc(sizeof(BufferCachePagesContext));
+ funcctx->max_calls = NBuffers;
+ funcctx->user_fctx = fctx;
+
+
+ /* Allocate NBuffers worth of BufferCachePagesRec records. */
+ fctx->record = (BufferCachePagesRec *) palloc(sizeof(BufferCachePagesRec) * NBuffers);
+
+ /* allocate the strings for tuple formation */
+ fctx->values[0] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[1] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[2] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[3] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[4] = (char *) palloc(3 * sizeof(uint32) + 1);
+ fctx->values[5] = (char *) palloc(2);
+
+
+ /* Return to original context when allocating transient memory */
+ MemoryContextSwitchTo(oldcontext);
+
+
+ /*
+ * Lock Buffer manager and scan though all the buffers, saving the
+ * relevant fields in the fctx->record structure.
+ */
+ LWLockAcquire(BufMgrLock, LW_SHARED);
+
+ for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
+ {
+
+ rnode = bufHdr->tag.rnode;
+
+ fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
+ fctx->record[i].relfilenode = rnode.relNode;
+ fctx->record[i].reltablespace = rnode.spcNode;
+ fctx->record[i].reldatabase = rnode.dbNode;
+ fctx->record[i].blocknum = bufHdr->tag.blockNum;
+
+ if ( bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
+ {
+ fctx->record[i].isdirty = true;
+ }
+ else
+ {
+ fctx->record[i].isdirty = false;
+ }
+
+ /* Note if the buffer is valid */
+ if ( (bufHdr->flags & BM_VALID))
+ {
+ fctx->record[i].isvalid = true;
+ }
+ else
+ {
+ fctx->record[i].isvalid = false;
+ }
+
+
+ }
+
+ /* Release Buffer manager. */
+ LWLockRelease(BufMgrLock);
+ }
+
+ funcctx = SRF_PERCALL_SETUP();
+
+ /* Get the saved state */
+ fctx = funcctx->user_fctx;
+
+
+ if (funcctx->call_cntr < funcctx->max_calls)
+ {
+ uint32 i = funcctx->call_cntr;
+ char *values[NUM_BUFFERCACHE_PAGES_ELEM];
+ int j;
+
+ /*
+ * Use a temporary values array, initially pointing to
+ * fctx->values, so it can be reassigned w/o losing the storage
+ * for subsequent calls.
+ */
+ for (j = 0; j < NUM_BUFFERCACHE_PAGES_ELEM; j++)
+ {
+ values[j] = fctx->values[j];
+ }
+
+
+ /*
+ * Set all fields except the bufferid to null if the buffer is
+ * unused or not valid.
+ */
+ if (fctx->record[i].blocknum == InvalidBlockNumber ||
+ fctx->record[i].isvalid == false )
+ {
+
+ sprintf(values[0], "%u", fctx->record[i].bufferid);
+ values[1] = NULL;
+ values[2] = NULL;
+ values[3] = NULL;
+ values[4] = NULL;
+ values[5] = NULL;
+
+ }
+ else
+ {
+
+ sprintf(values[0], "%u", fctx->record[i].bufferid);
+ sprintf(values[1], "%u", fctx->record[i].relfilenode);
+ sprintf(values[2], "%u", fctx->record[i].reltablespace);
+ sprintf(values[3], "%u", fctx->record[i].reldatabase);
+ sprintf(values[4], "%u", fctx->record[i].blocknum);
+ if (fctx->record[i].isdirty)
+ {
+ strcpy(values[5], "t");
+ }
+ else
+ {
+ strcpy(values[5], "f");
+ }
+
+ }
+
+
+ /* Build and return the tuple. */
+ tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
+ result = HeapTupleGetDatum(tuple);
+
+
+ SRF_RETURN_NEXT(funcctx, result);
+ }
+ else
+ SRF_RETURN_DONE(funcctx);
+
+}
+



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On Tue, 2005-05-31 at 13:07 +1200, Mark Kirkwood wrote:
> I did some patches for 7.4 and 8.0 a while ago (attached) - while I do
> not expect these to be applied

Right, I don't see a need to backport this.

> is there somewhere for things like this to go?

Pg Foundry?

-Neil



---------------------------(end of broadcast)---------------------------
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Neil Conway wrote:
> On Tue, 2005-05-31 at 13:07 +1200, Mark Kirkwood wrote:
>
>>I did some patches for 7.4 and 8.0 a while ago (attached) - while I do
>>not expect these to be applied
>
>
> Right, I don't see a need to backport this.
>
>
>>is there somewhere for things like this to go?
>
>
> Pg Foundry?
>
>
Of course! Thanks


Mark


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