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Diffstat (limited to '')
-rw-r--r-- | contrib/pg_buffercache/pg_buffercache_pages.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c new file mode 100644 index 0000000..1bd579f --- /dev/null +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -0,0 +1,239 @@ +/*------------------------------------------------------------------------- + * + * pg_buffercache_pages.c + * display some contents of the buffer cache + * + * contrib/pg_buffercache/pg_buffercache_pages.c + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "access/htup_details.h" +#include "catalog/pg_type.h" +#include "funcapi.h" +#include "storage/buf_internals.h" +#include "storage/bufmgr.h" + + +#define NUM_BUFFERCACHE_PAGES_MIN_ELEM 8 +#define NUM_BUFFERCACHE_PAGES_ELEM 9 + +PG_MODULE_MAGIC; + +/* + * Record structure holding the to be exposed cache data. + */ +typedef struct +{ + uint32 bufferid; + Oid relfilenode; + Oid reltablespace; + Oid reldatabase; + ForkNumber forknum; + BlockNumber blocknum; + bool isvalid; + bool isdirty; + uint16 usagecount; + + /* + * An int32 is sufficiently large, as MAX_BACKENDS prevents a buffer from + * being pinned by too many backends and each backend will only pin once + * because of bufmgr.c's PrivateRefCount infrastructure. + */ + int32 pinning_backends; +} BufferCachePagesRec; + + +/* + * Function context for data persisting over repeated calls. + */ +typedef struct +{ + TupleDesc tupdesc; + BufferCachePagesRec *record; +} 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; + TupleDesc expected_tupledesc; + HeapTuple tuple; + + if (SRF_IS_FIRSTCALL()) + { + int i; + + funcctx = SRF_FIRSTCALL_INIT(); + + /* Switch context when allocating stuff to be used in later calls */ + oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); + + /* Create a user function context for cross-call persistence */ + fctx = (BufferCachePagesContext *) palloc(sizeof(BufferCachePagesContext)); + + /* + * To smoothly support upgrades from version 1.0 of this extension + * transparently handle the (non-)existence of the pinning_backends + * column. We unfortunately have to get the result type for that... - + * we can't use the result type determined by the function definition + * without potentially crashing when somebody uses the old (or even + * wrong) function definition though. + */ + if (get_call_result_type(fcinfo, NULL, &expected_tupledesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + if (expected_tupledesc->natts < NUM_BUFFERCACHE_PAGES_MIN_ELEM || + expected_tupledesc->natts > NUM_BUFFERCACHE_PAGES_ELEM) + elog(ERROR, "incorrect number of output arguments"); + + /* Construct a tuple descriptor for the result rows. */ + tupledesc = CreateTemplateTupleDesc(expected_tupledesc->natts); + 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, "relforknumber", + INT2OID, -1, 0); + TupleDescInitEntry(tupledesc, (AttrNumber) 6, "relblocknumber", + INT8OID, -1, 0); + TupleDescInitEntry(tupledesc, (AttrNumber) 7, "isdirty", + BOOLOID, -1, 0); + TupleDescInitEntry(tupledesc, (AttrNumber) 8, "usage_count", + INT2OID, -1, 0); + + if (expected_tupledesc->natts == NUM_BUFFERCACHE_PAGES_ELEM) + TupleDescInitEntry(tupledesc, (AttrNumber) 9, "pinning_backends", + INT4OID, -1, 0); + + fctx->tupdesc = BlessTupleDesc(tupledesc); + + /* Allocate NBuffers worth of BufferCachePagesRec records. */ + fctx->record = (BufferCachePagesRec *) + MemoryContextAllocHuge(CurrentMemoryContext, + sizeof(BufferCachePagesRec) * NBuffers); + + /* Set max calls and remember the user function context. */ + funcctx->max_calls = NBuffers; + funcctx->user_fctx = fctx; + + /* Return to original context when allocating transient memory */ + MemoryContextSwitchTo(oldcontext); + + /* + * Scan through all the buffers, saving the relevant fields in the + * fctx->record structure. + * + * We don't hold the partition locks, so we don't get a consistent + * snapshot across all buffers, but we do grab the buffer header + * locks, so the information of each buffer is self-consistent. + */ + for (i = 0; i < NBuffers; i++) + { + BufferDesc *bufHdr; + uint32 buf_state; + + bufHdr = GetBufferDescriptor(i); + /* Lock each buffer header before inspecting. */ + buf_state = LockBufHdr(bufHdr); + + fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr); + fctx->record[i].relfilenode = bufHdr->tag.rnode.relNode; + fctx->record[i].reltablespace = bufHdr->tag.rnode.spcNode; + fctx->record[i].reldatabase = bufHdr->tag.rnode.dbNode; + fctx->record[i].forknum = bufHdr->tag.forkNum; + fctx->record[i].blocknum = bufHdr->tag.blockNum; + fctx->record[i].usagecount = BUF_STATE_GET_USAGECOUNT(buf_state); + fctx->record[i].pinning_backends = BUF_STATE_GET_REFCOUNT(buf_state); + + if (buf_state & BM_DIRTY) + fctx->record[i].isdirty = true; + else + fctx->record[i].isdirty = false; + + /* Note if the buffer is valid, and has storage created */ + if ((buf_state & BM_VALID) && (buf_state & BM_TAG_VALID)) + fctx->record[i].isvalid = true; + else + fctx->record[i].isvalid = false; + + UnlockBufHdr(bufHdr, buf_state); + } + } + + funcctx = SRF_PERCALL_SETUP(); + + /* Get the saved state */ + fctx = funcctx->user_fctx; + + if (funcctx->call_cntr < funcctx->max_calls) + { + uint32 i = funcctx->call_cntr; + Datum values[NUM_BUFFERCACHE_PAGES_ELEM]; + bool nulls[NUM_BUFFERCACHE_PAGES_ELEM]; + + values[0] = Int32GetDatum(fctx->record[i].bufferid); + nulls[0] = false; + + /* + * 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) + { + nulls[1] = true; + nulls[2] = true; + nulls[3] = true; + nulls[4] = true; + nulls[5] = true; + nulls[6] = true; + nulls[7] = true; + /* unused for v1.0 callers, but the array is always long enough */ + nulls[8] = true; + } + else + { + values[1] = ObjectIdGetDatum(fctx->record[i].relfilenode); + nulls[1] = false; + values[2] = ObjectIdGetDatum(fctx->record[i].reltablespace); + nulls[2] = false; + values[3] = ObjectIdGetDatum(fctx->record[i].reldatabase); + nulls[3] = false; + values[4] = ObjectIdGetDatum(fctx->record[i].forknum); + nulls[4] = false; + values[5] = Int64GetDatum((int64) fctx->record[i].blocknum); + nulls[5] = false; + values[6] = BoolGetDatum(fctx->record[i].isdirty); + nulls[6] = false; + values[7] = Int16GetDatum(fctx->record[i].usagecount); + nulls[7] = false; + /* unused for v1.0 callers, but the array is always long enough */ + values[8] = Int32GetDatum(fctx->record[i].pinning_backends); + nulls[8] = false; + } + + /* Build and return the tuple. */ + tuple = heap_form_tuple(fctx->tupdesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + SRF_RETURN_NEXT(funcctx, result); + } + else + SRF_RETURN_DONE(funcctx); +} |