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commit    8fd5aa76c3673348437f4779ba3bd710eadb44f2
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Thu Mar 23 19:29:28 2023 +0000

    amcheck: Fix verify_heapam for tuples where xmin or xmax is 0.
    
    In such cases, get_xid_status() doesn't set its output parameter (the
    third argument), so we shouldn't fall through to code which will test
    the value of that parameter. There are five existing calls to
    get_xid_status(), three of which seem to already handle this case
    properly.  This commit tries to fix the other two.
    
    If we're checking xmin and find that it is invalid (i.e. 0) just
    report that as corruption, similar to what's already done in the
    three cases that seem correct. If we're checking xmax and find
    that's invalid, that's fine: it just means that the tuple hasn't
    been updated or deleted.
    
    Thanks to Andres Freund and valgrind for finding this problem, and
    also to Andres for having a look at the patch.  This bug seems to go
    all the way back to where verify_heapam was first introduced, but
    wasn't detected until recently, possibly because of the new test cases
    added for update chain verification.  Back-patch to v14, where this
    code showed up.
    
    Discussion: http://postgr.es/m/CA+TgmoZAYzQZqyUparXy_ks3OEOfLD9-bEXt8N-2tS1qghX9gQ@mail.gmail.com


 contrib/amcheck/verify_heapam.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/contrib/amcheck/verify_heapam.c b/contrib/amcheck/verify_heapam.c
index 7a51aba3314..69230f76499 100644
--- a/contrib/amcheck/verify_heapam.c
+++ b/contrib/amcheck/verify_heapam.c
@@ -774,6 +774,9 @@ check_tuple_visibility(HeapCheckContext *ctx)
 	switch (get_xid_status(xmin, ctx, &xmin_status))
 	{
 		case XID_INVALID:
+			report_corruption(ctx,
+							  pstrdup("xmin is invalid"));
+			return false;
 		case XID_BOUNDS_OK:
 			break;
 		case XID_IN_FUTURE:
@@ -1109,6 +1112,9 @@ check_tuple_visibility(HeapCheckContext *ctx)
 	xmax = HeapTupleHeaderGetRawXmax(tuphdr);
 	switch (get_xid_status(xmax, ctx, &xmax_status))
 	{
+		case XID_INVALID:
+			ctx->tuple_could_be_pruned = false;
+			return true;
 		case XID_IN_FUTURE:
 			report_corruption(ctx,
 							  psprintf("xmax %u equals or exceeds next valid transaction ID %u:%u",
@@ -1131,7 +1137,6 @@ check_tuple_visibility(HeapCheckContext *ctx)
 									   XidFromFullTransactionId(ctx->oldest_fxid)));
 			return false;		/* corrupt */
 		case XID_BOUNDS_OK:
-		case XID_INVALID:
 			break;
 	}
 


[parent: 9dac02c77258]