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From: Jianghua Yang <[email protected]>
To: [email protected]
Subject: BUG: test_ginpostinglist second itemptr check is a no-op due to copy-paste error
Date: Mon, 23 Mar 2026 18:44:40 -0700
Message-ID: <CAAZLFmSOD8R7tZjRLZsmpKtJLoqjgawAaM-Pne1j8B_Q2aQK8w@mail.gmail.com> (raw)

 Hi,

  I found a copy-paste bug in
src/test/modules/test_ginpostinglist/test_ginpostinglist.c.

  The function test_itemptr_pair() encodes a pair of item pointers and
  decodes them back to verify the round-trip. The two original item
  pointers are:

  orig_itemptrs[0] = (0, 1)
  orig_itemptrs[1] = (blk, off)

  After the first itemptr check (lines 68-72), there is a second check
  intended to verify the second decoded item pointer when ndecoded == 2:

  if (ndecoded == 2 &&
      !ItemPointerEquals(&orig_itemptrs[0], &decoded_itemptrs[0]))
  {
      elog(ERROR, "mismatch on second itemptr: (%u, %d) vs (%u, %d)",
           0, 1,
           ItemPointerGetBlockNumber(&decoded_itemptrs[0]),
           ItemPointerGetOffsetNumber(&decoded_itemptrs[0]));
  }

  This is an exact duplicate of the first check — it uses index [0]
  throughout, and the expected value is hardcoded as (0, 1) instead of
  (blk, off). As a result, any decoding error in decoded_itemptrs[1]
  would go undetected.

  This is particularly unfortunate because the whole purpose of testing a
  pair (as the comment at line 30-33 explains) is to exercise the varbyte
  delta encoding, which only applies to the second and subsequent item
  pointers. The broken check defeats exactly that goal.

  The attached patch fixes the second check to compare orig_itemptrs[1]
  with decoded_itemptrs[1] and reports (blk, off) as the expected
  value in the error message.

  Regards,
  Jianghua Yang


Attachments:

  [application/octet-stream] v1-0001-Fix-copy-paste-error-in-test_ginpostinglist-secon.patch (1.7K, 3-v1-0001-Fix-copy-paste-error-in-test_ginpostinglist-secon.patch)
  download | inline diff:
From dda3c6611ef5fd4a619b8284e56a990b9e0fefe7 Mon Sep 17 00:00:00 2001
From: Jianghua Yang <[email protected]>
Date: Mon, 23 Mar 2026 18:29:54 -0700
Subject: [PATCH v1] Fix copy-paste error in test_ginpostinglist second itemptr
 check

The check for a mismatch on the second decoded item pointer was an
exact copy of the first item pointer check, comparing orig_itemptrs[0]
with decoded_itemptrs[0] instead of orig_itemptrs[1] with
decoded_itemptrs[1].  The error message also reported (0, 1) as the
expected value instead of (blk, off).  As a result, any decoding error
in the second item pointer (where the varbyte delta encoding is
exercised) would go undetected.

Author: Jianghua Yang <[email protected]>
---
 .../modules/test_ginpostinglist/test_ginpostinglist.c     | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/test/modules/test_ginpostinglist/test_ginpostinglist.c b/src/test/modules/test_ginpostinglist/test_ginpostinglist.c
index 83cf3469886..6d84364f5c5 100644
--- a/src/test/modules/test_ginpostinglist/test_ginpostinglist.c
+++ b/src/test/modules/test_ginpostinglist/test_ginpostinglist.c
@@ -72,12 +72,12 @@ test_itemptr_pair(BlockNumber blk, OffsetNumber off, int maxsize)
 			 ItemPointerGetOffsetNumber(&decoded_itemptrs[0]));
 
 	if (ndecoded == 2 &&
-		!ItemPointerEquals(&orig_itemptrs[0], &decoded_itemptrs[0]))
+		!ItemPointerEquals(&orig_itemptrs[1], &decoded_itemptrs[1]))
 	{
 		elog(ERROR, "mismatch on second itemptr: (%u, %d) vs (%u, %d)",
-			 0, 1,
-			 ItemPointerGetBlockNumber(&decoded_itemptrs[0]),
-			 ItemPointerGetOffsetNumber(&decoded_itemptrs[0]));
+			 blk, off,
+			 ItemPointerGetBlockNumber(&decoded_itemptrs[1]),
+			 ItemPointerGetOffsetNumber(&decoded_itemptrs[1]));
 	}
 }
 
-- 
2.50.1 (Apple Git-155)

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  Subject: Re: BUG: test_ginpostinglist second itemptr check is a no-op due to copy-paste error
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