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This reduces unnecessary exposure of other headers through htup.h, which is very widely included by many files. I have chosen to move the function prototypes to the new file as well, because that means htup.h no longer needs to include tupdesc.h. In itself this doesn't have much effect in indirect inclusion of tupdesc.h throughout the tree, because it's also required by execnodes.h; but it's something to explore in the future, and it seemed best to do the htup.h change now while I'm busy with it.
219 lines
6.2 KiB
C
219 lines
6.2 KiB
C
/*-------------------------------------------------------------------------
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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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* contrib/pg_buffercache/pg_buffercache_pages.c
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/htup_details.h"
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#include "catalog/pg_type.h"
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#include "funcapi.h"
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#include "storage/buf_internals.h"
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#include "storage/bufmgr.h"
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#define NUM_BUFFERCACHE_PAGES_ELEM 8
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PG_MODULE_MAGIC;
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Datum pg_buffercache_pages(PG_FUNCTION_ARGS);
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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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ForkNumber forknum;
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BlockNumber blocknum;
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bool isvalid;
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bool isdirty;
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uint16 usagecount;
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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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TupleDesc tupdesc;
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BufferCachePagesRec *record;
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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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int i;
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volatile 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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/* Create a user function context for cross-call persistence */
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fctx = (BufferCachePagesContext *) palloc(sizeof(BufferCachePagesContext));
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/* Construct a tuple descriptor for the result rows. */
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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, "relforknumber",
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INT2OID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 6, "relblocknumber",
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INT8OID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 7, "isdirty",
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BOOLOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 8, "usage_count",
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INT2OID, -1, 0);
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fctx->tupdesc = BlessTupleDesc(tupledesc);
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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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/* Set max calls and remember the user function context. */
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funcctx->max_calls = NBuffers;
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funcctx->user_fctx = fctx;
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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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* To get a consistent picture of the buffer state, we must lock all
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* partitions of the buffer map. Needless to say, this is horrible
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* for concurrency. Must grab locks in increasing order to avoid
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* possible deadlocks.
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*/
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for (i = 0; i < NUM_BUFFER_PARTITIONS; i++)
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LWLockAcquire(FirstBufMappingLock + i, LW_SHARED);
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/*
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* Scan though all the buffers, saving the relevant fields in the
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* fctx->record structure.
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*/
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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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fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
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fctx->record[i].relfilenode = bufHdr->tag.rnode.relNode;
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fctx->record[i].reltablespace = bufHdr->tag.rnode.spcNode;
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fctx->record[i].reldatabase = bufHdr->tag.rnode.dbNode;
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fctx->record[i].forknum = bufHdr->tag.forkNum;
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fctx->record[i].blocknum = bufHdr->tag.blockNum;
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fctx->record[i].usagecount = bufHdr->usage_count;
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if (bufHdr->flags & BM_DIRTY)
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fctx->record[i].isdirty = true;
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else
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fctx->record[i].isdirty = false;
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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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fctx->record[i].isvalid = true;
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else
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fctx->record[i].isvalid = false;
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UnlockBufHdr(bufHdr);
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}
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/*
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* And release locks. We do this in reverse order for two reasons:
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* (1) Anyone else who needs more than one of the locks will be trying
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* to lock them in increasing order; we don't want to release the
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* other process until it can get all the locks it needs. (2) This
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* avoids O(N^2) behavior inside LWLockRelease.
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*/
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for (i = NUM_BUFFER_PARTITIONS; --i >= 0;)
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LWLockRelease(FirstBufMappingLock + i);
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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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Datum values[NUM_BUFFERCACHE_PAGES_ELEM];
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bool nulls[NUM_BUFFERCACHE_PAGES_ELEM];
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values[0] = Int32GetDatum(fctx->record[i].bufferid);
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nulls[0] = false;
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/*
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* Set all fields except the bufferid to null if the buffer is unused
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* 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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nulls[1] = true;
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nulls[2] = true;
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nulls[3] = true;
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nulls[4] = true;
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nulls[5] = true;
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nulls[6] = true;
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nulls[7] = true;
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}
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else
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{
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values[1] = ObjectIdGetDatum(fctx->record[i].relfilenode);
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nulls[1] = false;
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values[2] = ObjectIdGetDatum(fctx->record[i].reltablespace);
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nulls[2] = false;
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values[3] = ObjectIdGetDatum(fctx->record[i].reldatabase);
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nulls[3] = false;
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values[4] = ObjectIdGetDatum(fctx->record[i].forknum);
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nulls[4] = false;
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values[5] = Int64GetDatum((int64) fctx->record[i].blocknum);
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nulls[5] = false;
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values[6] = BoolGetDatum(fctx->record[i].isdirty);
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nulls[6] = false;
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values[7] = Int16GetDatum(fctx->record[i].usagecount);
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nulls[7] = false;
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}
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/* Build and return the tuple. */
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tuple = heap_form_tuple(fctx->tupdesc, values, nulls);
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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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