diff options
Diffstat (limited to 'contrib/pg_buffercache/pg_buffercache_pages.c')
| -rw-r--r-- | contrib/pg_buffercache/pg_buffercache_pages.c | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c index b205683bffc..d3b1ba3245d 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -15,7 +15,8 @@ #include "storage/bufmgr.h" -#define NUM_BUFFERCACHE_PAGES_ELEM 8 +#define NUM_BUFFERCACHE_PAGES_MIN_ELEM 8 +#define NUM_BUFFERCACHE_PAGES_ELEM 9 PG_MODULE_MAGIC; @@ -33,6 +34,12 @@ typedef struct 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 array. + */ + int32 pinning_backends; } BufferCachePagesRec; @@ -60,6 +67,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) MemoryContext oldcontext; BufferCachePagesContext *fctx; /* User function context. */ TupleDesc tupledesc; + TupleDesc expected_tupledesc; HeapTuple tuple; if (SRF_IS_FIRSTCALL()) @@ -75,8 +83,23 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) /* 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-)existance 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(NUM_BUFFERCACHE_PAGES_ELEM, false); + tupledesc = CreateTemplateTupleDesc(expected_tupledesc->natts, false); TupleDescInitEntry(tupledesc, (AttrNumber) 1, "bufferid", INT4OID, -1, 0); TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode", @@ -94,6 +117,10 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) 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. */ @@ -131,6 +158,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) fctx->record[i].forknum = bufHdr->tag.forkNum; fctx->record[i].blocknum = bufHdr->tag.blockNum; fctx->record[i].usagecount = bufHdr->usage_count; + fctx->record[i].pinning_backends = bufHdr->refcount; if (bufHdr->flags & BM_DIRTY) fctx->record[i].isdirty = true; @@ -185,6 +213,8 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) 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 { @@ -202,6 +232,9 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) 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. */ |