From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 7 Jul 2011 19:05:21 +0000 (-0400)
Subject: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.
X-Git-Tag: REL9_1_BETA3~7
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a392b5247870da806e511ae2aadb0464509f7afe;p=postgresql

Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.

The value when BLCKSZ = 8192 is unchanged, but with larger-than-normal
block sizes we might need to crank things back a bit, as we'll have
more entries per page than normal in that case.

Kevin Grittner
---

diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index f0c8ee48c3..7f6dcbb6ca 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -305,7 +305,13 @@ static SlruCtlData OldSerXidSlruCtlData;
 #define OLDSERXID_PAGESIZE			BLCKSZ
 #define OLDSERXID_ENTRYSIZE			sizeof(SerCommitSeqNo)
 #define OLDSERXID_ENTRIESPERPAGE	(OLDSERXID_PAGESIZE / OLDSERXID_ENTRYSIZE)
-#define OLDSERXID_MAX_PAGE			(SLRU_PAGES_PER_SEGMENT * 0x10000 - 1)
+
+/*
+ * Set maximum pages based on the lesser of the number needed to track all
+ * transactions and the maximum that SLRU supports.
+ */
+#define OLDSERXID_MAX_PAGE			Min(SLRU_PAGES_PER_SEGMENT * 0x10000 - 1, \
+										(MaxTransactionId + 1) / OLDSERXID_ENTRIESPERPAGE - 1)
 
 #define OldSerXidNextPage(page) (((page) >= OLDSERXID_MAX_PAGE) ? 0 : (page) + 1)