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Add pg_buffercache contrib module, from Mark Kirkwood.
This commit is contained in:
Neil Conway
238
contrib/pg_buffercache/pg_buffercache_pages.c
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238
contrib/pg_buffercache/pg_buffercache_pages.c
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/*-------------------------------------------------------------------------
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*
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* pg_buffercache_pages.c
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* display some contents of the buffer cache
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*
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* $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.1 2005/03/12 15:36:24 neilc Exp $
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "funcapi.h"
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#include "catalog/pg_type.h"
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#include "storage/buf_internals.h"
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#include "storage/bufmgr.h"
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#include "utils/relcache.h"
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#include "pg_buffercache_pages.h"
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#define NUM_BUFFERCACHE_PAGES_ELEM 6
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/*
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* Record structure holding the to be exposed cache data.
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*/
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typedef struct
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{
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uint32 bufferid;
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Oid relfilenode;
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Oid reltablespace;
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Oid reldatabase;
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BlockNumber blocknum;
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bool isvalid;
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bool isdirty;
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} BufferCachePagesRec;
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/*
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* Function context for data persisting over repeated calls.
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*/
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typedef struct
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{
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AttInMetadata *attinmeta;
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BufferCachePagesRec *record;
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char *values[NUM_BUFFERCACHE_PAGES_ELEM];
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} BufferCachePagesContext;
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/*
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* Function returning data from the shared buffer cache - buffer number,
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* relation node/tablespace/database/blocknum and dirty indicator.
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*/
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PG_FUNCTION_INFO_V1(pg_buffercache_pages);
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Datum
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pg_buffercache_pages(PG_FUNCTION_ARGS)
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{
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FuncCallContext *funcctx;
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Datum result;
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MemoryContext oldcontext;
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BufferCachePagesContext *fctx; /* User function context. */
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TupleDesc tupledesc;
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HeapTuple tuple;
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if (SRF_IS_FIRSTCALL())
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{
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RelFileNode rnode;
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uint32 i;
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BufferDesc *bufHdr;
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funcctx = SRF_FIRSTCALL_INIT();
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/* Switch context when allocating stuff to be used in later calls */
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oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
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/* Construct a tuple to return. */
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tupledesc = CreateTemplateTupleDesc(NUM_BUFFERCACHE_PAGES_ELEM, false);
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TupleDescInitEntry(tupledesc, (AttrNumber) 1, "bufferid",
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INT4OID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reltablespace",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblockbumber",
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NUMERICOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 6, "isdirty",
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BOOLOID, -1, 0);
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/* Generate attribute metadata needed later to produce tuples */
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funcctx->attinmeta = TupleDescGetAttInMetadata(tupledesc);
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/*
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* Create a function context for cross-call persistence
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* and initialize the buffer counters.
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*/
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fctx = (BufferCachePagesContext *) palloc(sizeof(BufferCachePagesContext));
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funcctx->max_calls = NBuffers;
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funcctx->user_fctx = fctx;
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/* Allocate NBuffers worth of BufferCachePagesRec records. */
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fctx->record = (BufferCachePagesRec *) palloc(sizeof(BufferCachePagesRec) * NBuffers);
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/* allocate the strings for tuple formation */
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fctx->values[0] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[1] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[2] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[3] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[4] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[5] = (char *) palloc(2);
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/* Return to original context when allocating transient memory */
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MemoryContextSwitchTo(oldcontext);
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/*
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* Lock Buffer map and scan though all the buffers, saving the
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* relevant fields in the fctx->record structure.
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*/
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LWLockAcquire(BufMappingLock, LW_SHARED);
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for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
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{
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/* Lock each buffer header before inspecting. */
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LockBufHdr(bufHdr);
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rnode = bufHdr->tag.rnode;
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fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
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fctx->record[i].relfilenode = rnode.relNode;
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fctx->record[i].reltablespace = rnode.spcNode;
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fctx->record[i].reldatabase = rnode.dbNode;
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fctx->record[i].blocknum = bufHdr->tag.blockNum;
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if ( bufHdr->flags & BM_DIRTY)
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{
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fctx->record[i].isdirty = true;
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}
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else
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{
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fctx->record[i].isdirty = false;
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}
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/* Note if the buffer is valid, and has storage created */
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if ( (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_TAG_VALID))
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{
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fctx->record[i].isvalid = true;
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}
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else
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{
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fctx->record[i].isvalid = false;
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}
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UnlockBufHdr(bufHdr);
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}
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/* Release Buffer map. */
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LWLockRelease(BufMappingLock);
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}
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funcctx = SRF_PERCALL_SETUP();
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/* Get the saved state */
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fctx = funcctx->user_fctx;
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if (funcctx->call_cntr < funcctx->max_calls)
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{
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uint32 i = funcctx->call_cntr;
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char *values[NUM_BUFFERCACHE_PAGES_ELEM];
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int j;
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/*
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* Use a temporary values array, initially pointing to
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* fctx->values, so it can be reassigned w/o losing the storage
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* for subsequent calls.
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*/
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for (j = 0; j < NUM_BUFFERCACHE_PAGES_ELEM; j++)
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{
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values[j] = fctx->values[j];
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}
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/*
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* Set all fields except the bufferid to null if the buffer is
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* unused or not valid.
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*/
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if (fctx->record[i].blocknum == InvalidBlockNumber ||
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fctx->record[i].isvalid == false )
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{
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sprintf(values[0], "%u", fctx->record[i].bufferid);
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values[1] = NULL;
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values[2] = NULL;
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values[3] = NULL;
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values[4] = NULL;
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values[5] = NULL;
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}
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else
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{
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sprintf(values[0], "%u", fctx->record[i].bufferid);
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sprintf(values[1], "%u", fctx->record[i].relfilenode);
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sprintf(values[2], "%u", fctx->record[i].reltablespace);
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sprintf(values[3], "%u", fctx->record[i].reldatabase);
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sprintf(values[4], "%u", fctx->record[i].blocknum);
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if (fctx->record[i].isdirty)
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{
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strcpy(values[5], "t");
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}
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else
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{
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strcpy(values[5], "f");
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}
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}
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/* Build and return the tuple. */
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tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
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result = HeapTupleGetDatum(tuple);
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SRF_RETURN_NEXT(funcctx, result);
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}
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else
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SRF_RETURN_DONE(funcctx);
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}
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