From: Simon Riggs <simon@2ndQuadrant.com>
Date: Fri, 25 Sep 2009 11:47:15 +0000 (+0100)
Subject: Clarify Hot Standby processing for GIN and GIST indexes by more descriptive comments.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=4288ceb09523813cb69de409ab169cc6fa41502a;p=users%2Fsimon%2Fpostgres.git

Clarify Hot Standby processing for GIN and GIST indexes by more descriptive comments.
---

diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index 94b72024b7..46cc5f1792 100644
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -622,7 +622,9 @@ gin_redo(XLogRecPtr lsn, XLogRecord *record)
 	uint8		info = record->xl_info & ~XLR_INFO_MASK;
 
 	/*
-	 * GIN indexes do not require any conflict processing. XXX really?
+	 * GIN indexes do not require any conflict processing. The GIN
+	 * posting tree is scanned in logical order during VACUUM and
+	 * no additional processing is required.
 	 */
 	if (InHotStandby)
 		RecordKnownAssignedTransactionIds(record->xl_xid);
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index 3e5f3b65e7..4bca49324f 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -397,7 +397,10 @@ gist_redo(XLogRecPtr lsn, XLogRecord *record)
 	MemoryContext oldCxt;
 
 	/*
-	 * GIST indexes do not require any conflict processing. XXX really?
+	 * GIST indexes do not require any conflict processing. This is
+	 * because GIST does not remove killed tuples when it performs
+	 * page splits in the same way b-trees do. Also VACUUMs of 
+	 * GIST indexes occur in logical not physical order.
 	 */
 	if (InHotStandby)
 		RecordKnownAssignedTransactionIds(record->xl_xid);