From fb3dbdf986f0ab56e0a5177966bb0dec1f93444c Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Fri, 16 Dec 2005 04:03:40 +0000
Subject: Rethink prior patch to filter out dead backend entries from the
 pgstats file.  The original code probed the PGPROC array separately for each
 PID, which was not good for large numbers of backends: not only is the
 runtime O(N^2) but most of it is spent holding ProcArrayLock.  Instead, take
 the lock just once and copy the active PIDs into an array, then use qsort and
 bsearch so that the lookup time is more like O(N log N).

---
 src/include/storage/procarray.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'src/include')

diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index 68c615afc6e..61441bbf49e 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.6 2005/10/15 02:49:46 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.7 2005/12/16 04:03:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,7 @@ extern TransactionId GetOldestXmin(bool allDbs);
 extern PGPROC *BackendPidGetProc(int pid);
 extern int	BackendXidGetPid(TransactionId xid);
 extern bool IsBackendPid(int pid);
+extern int *GetAllBackendPids(void);
 extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
 
 extern int	CountActiveBackends(void);
-- 
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