diff options
Diffstat (limited to 'contrib/pg_buffercache/pg_buffercache_pages.c')
| -rw-r--r-- | contrib/pg_buffercache/pg_buffercache_pages.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c index c5754ea9fa5..1c6a2f22caa 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -17,6 +17,7 @@ #define NUM_BUFFERCACHE_PAGES_MIN_ELEM 8 #define NUM_BUFFERCACHE_PAGES_ELEM 9 +#define NUM_BUFFERCACHE_SUMMARY_ELEM 5 PG_MODULE_MAGIC; @@ -59,6 +60,7 @@ typedef struct * relation node/tablespace/database/blocknum and dirty indicator. */ PG_FUNCTION_INFO_V1(pg_buffercache_pages); +PG_FUNCTION_INFO_V1(pg_buffercache_summary); Datum pg_buffercache_pages(PG_FUNCTION_ARGS) @@ -237,3 +239,68 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) else SRF_RETURN_DONE(funcctx); } + +Datum +pg_buffercache_summary(PG_FUNCTION_ARGS) +{ + Datum result; + TupleDesc tupledesc; + HeapTuple tuple; + Datum values[NUM_BUFFERCACHE_SUMMARY_ELEM]; + bool nulls[NUM_BUFFERCACHE_SUMMARY_ELEM]; + + int32 buffers_used = 0; + int32 buffers_unused = 0; + int32 buffers_dirty = 0; + int32 buffers_pinned = 0; + int64 usagecount_total = 0; + + if (get_call_result_type(fcinfo, NULL, &tupledesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + for (int i = 0; i < NBuffers; i++) + { + BufferDesc *bufHdr; + uint32 buf_state; + + /* + * This function summarizes the state of all headers. Locking the + * buffer headers wouldn't provide an improved result as the state of + * the buffer can still change after we release the lock and it'd + * noticeably increase the cost of the function. + */ + bufHdr = GetBufferDescriptor(i); + buf_state = pg_atomic_read_u32(&bufHdr->state); + + if (buf_state & BM_VALID) + { + buffers_used++; + usagecount_total += BUF_STATE_GET_USAGECOUNT(buf_state); + + if (buf_state & BM_DIRTY) + buffers_dirty++; + } + else + buffers_unused++; + + if (BUF_STATE_GET_REFCOUNT(buf_state) > 0) + buffers_pinned++; + } + + memset(nulls, 0, sizeof(nulls)); + values[0] = Int32GetDatum(buffers_used); + values[1] = Int32GetDatum(buffers_unused); + values[2] = Int32GetDatum(buffers_dirty); + values[3] = Int32GetDatum(buffers_pinned); + + if (buffers_used != 0) + values[4] = Float8GetDatum((double) usagecount_total / buffers_used); + else + nulls[4] = true; + + /* Build and return the tuple. */ + tuple = heap_form_tuple(tupledesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + PG_RETURN_DATUM(result); +} |