From e4b66b962e7f4eaf85c1413eeae6c29df5ab8591 Mon Sep 17 00:00:00 2001
From: hvlad <hvlad@users.sourceforge.net>
Date: Wed, 14 Feb 2007 08:58:07 +0000
Subject: [PATCH] Fixed CORE-1127 : Circular index references in corrupt
 database causes fbserver to loop infinitely. Thanks to Diane Downie

---
 src/jrd/jrd.h          |  3 ++-
 src/jrd/validation.cpp | 15 ++++++++++++++-
 src/jrd/vio.cpp        | 11 +++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/jrd/jrd.h b/src/jrd/jrd.h
index b6f3bc7b0d..fd43866ae3 100644
--- a/src/jrd/jrd.h
+++ b/src/jrd/jrd.h
@@ -437,7 +437,8 @@ const int VAL_TIP_CONFUSED				= 21;
 const int VAL_REL_CHAIN_ORPHANS			= 22;
 const int VAL_INDEX_MISSING_ROWS		= 23;
 const int VAL_INDEX_ORPHAN_CHILD		= 24;
-const int VAL_MAX_ERROR					= 25;
+const int VAL_INDEX_CYCLE				= 25;
+const int VAL_MAX_ERROR					= 26;
 
 
 //
diff --git a/src/jrd/validation.cpp b/src/jrd/validation.cpp
index a91b66ad60..12fdd2693d 100644
--- a/src/jrd/validation.cpp
+++ b/src/jrd/validation.cpp
@@ -647,7 +647,8 @@ static const TEXT msg_table[][66] = {
 	"Transaction inventory pages confused, sequence %ld",
 	"Relation has %ld orphan backversions (%ld in use)",
 	"Index %d is corrupt (missing entries)",
-	"Index %d has orphan child page at page %ld"
+	"Index %d has orphan child page at page %ld",
+	"Index %d has a circular reference at page %ld"
 };
 
 
@@ -1430,11 +1431,16 @@ static RTN walk_index(thread_db* tdbb, vdr* control, jrd_rel* relation,
 	SCHAR flags = 0;
 	UCHAR* pointer;
 	IndexNode node, lastNode;
+	PageBitmap visited_pages; // used to check circular page references, Diane Downie 2/9/07
 
 	while (next) {
 		WIN window(-1);
 		btree_page* page = 0;
 		fetch_page(tdbb, control, next, pag_index, &window, &page);
+		
+		// remember each page for circular reference detection 
+		visited_pages.set(next); 
+		
 		if ((next != page_number) &&
 			(page->btr_header.pag_flags & BTR_FLAG_COPY_MASK) !=
 			(flags & BTR_FLAG_COPY_MASK))
@@ -1686,6 +1692,13 @@ static RTN walk_index(thread_db* tdbb, vdr* control, jrd_rel* relation,
 			nullKeyHandled = !(unique && null_key);
 		}
 
+		// check for circular referenes
+		if (next && visited_pages.test(next)) 
+		{
+			corrupt(tdbb, control, VAL_INDEX_CYCLE, relation,
+					id + 1, next);
+			next = 0;
+		}
 		CCH_RELEASE(tdbb, &window);
 	}
 
diff --git a/src/jrd/vio.cpp b/src/jrd/vio.cpp
index a816bf40a3..3daa33e963 100644
--- a/src/jrd/vio.cpp
+++ b/src/jrd/vio.cpp
@@ -768,6 +768,17 @@ bool VIO_chase_record_version(thread_db* tdbb, record_param* rpb, RecordSource*
 				CCH_RELEASE(tdbb, &rpb->rpb_window);
 				return false;
 			}
+
+			// hvlad: if i'm garbage collector i don't need to read backversion of active
+			// record. Just do notify self about it (if background policy enabled)
+			if (attachment->att_flags & ATT_garbage_collector)
+			{
+				// VIO_chase_record_version
+				notify_garbage_collector(tdbb, rpb);
+				CCH_RELEASE(tdbb, &rpb->rpb_window);
+				return false;
+			}
+
 			if (!(rpb->rpb_flags & rpb_delta)) {
 				rpb->rpb_prior = NULL;
 				/* Fetch a back version.  If a latch timeout occurs, refetch the