postgresql/contrib/pg_buffercache/pg_buffercache_pages.c

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/*-------------------------------------------------------------------------
*
* pg_buffercache_pages.c
* display some contents of the buffer cache
*
* $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.4 2005/05/31 00:07:47 tgl Exp $
*-------------------------------------------------------------------------
*/
#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
#if defined(WIN32) || defined(__CYGWIN__)
extern DLLIMPORT BufferDesc *BufferDescriptors;
extern DLLIMPORT volatile uint32 InterruptHoldoffCount;
#endif
Datum pg_buffercache_pages(PG_FUNCTION_ARGS);
/*
* 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, "relblocknumber",
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 map and scan though all the buffers, saving the
* relevant fields in the fctx->record structure.
*/
LWLockAcquire(BufMappingLock, LW_SHARED);
for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
{
/* Lock each buffer header before inspecting. */
LockBufHdr(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)
{
fctx->record[i].isdirty = true;
}
else
{
fctx->record[i].isdirty = false;
}
/* Note if the buffer is valid, and has storage created */
if ( (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_TAG_VALID))
{
fctx->record[i].isvalid = true;
}
else
{
fctx->record[i].isvalid = false;
}
UnlockBufHdr(bufHdr);
}
/* Release Buffer map. */
LWLockRelease(BufMappingLock);
}
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);
}