v2-0001-Fix-bugs-in-pg_wal_summary_contents.patch

From 47bcd6d19e45b98b006fff1b495c8b65bd84c377 Mon Sep 17 00:00:00 2001
From: Fujii Masao <fujii@postgresql.org>
Date: Wed, 3 Jul 2024 15:50:30 +0900
Subject: [PATCH v2] Fix bugs in pg_wal_summary_contents().

Previously, pg_wal_summary_contents() had two issues,
causing discrepancies between pg_wal_summary_contents()
and the pg_walsummary command on the same WAL summary file:

(1) It did not emit the limit block when that's the only data for
     a particular relation fork.
(2) It emitted the same limit block multiple times if the list of
     block numbers was long enough.

This commit fixes these bugs.

Backpatch to v17 where pg_wal_summary_contents() was added.

Author: Fujii Masao
Reviewed-by: Robert Haas
Discussion: https://postgr.es/m/90980ee6-2da6-42f6-a7b0-b7bae62ae279@oss.nttdata.com
---
 src/backend/backup/walsummaryfuncs.c | 34 ++++++++++++++--------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/backend/backup/walsummaryfuncs.c b/src/backend/backup/walsummaryfuncs.c
index f082488b33..bb6a3a4a36 100644
--- a/src/backend/backup/walsummaryfuncs.c
+++ b/src/backend/backup/walsummaryfuncs.c
@@ -118,6 +118,23 @@ pg_wal_summary_contents(PG_FUNCTION_ARGS)
 		values[2] = ObjectIdGetDatum(rlocator.dbOid);
 		values[3] = Int16GetDatum((int16) forknum);
 
+		/*
+		 * If the limit block is not InvalidBlockNumber, emit an extra row
+		 * with that block number and limit_block = true.
+		 *
+		 * There is no point in doing this when the limit_block is
+		 * InvalidBlockNumber, because no block with that number or any higher
+		 * number can ever exist.
+		 */
+		if (BlockNumberIsValid(limit_block))
+		{
+			values[4] = Int64GetDatum((int64) limit_block);
+			values[5] = BoolGetDatum(true);
+
+			tuple = heap_form_tuple(rsi->setDesc, values, nulls);
+			tuplestore_puttuple(rsi->setResult, tuple);
+		}
+
 		/* Loop over blocks within the current relation fork. */
 		while (1)
 		{
@@ -143,23 +160,6 @@ pg_wal_summary_contents(PG_FUNCTION_ARGS)
 				tuple = heap_form_tuple(rsi->setDesc, values, nulls);
 				tuplestore_puttuple(rsi->setResult, tuple);
 			}
-
-			/*
-			 * If the limit block is not InvalidBlockNumber, emit an extra row
-			 * with that block number and limit_block = true.
-			 *
-			 * There is no point in doing this when the limit_block is
-			 * InvalidBlockNumber, because no block with that number or any
-			 * higher number can ever exist.
-			 */
-			if (BlockNumberIsValid(limit_block))
-			{
-				values[4] = Int64GetDatum((int64) limit_block);
-				values[5] = BoolGetDatum(true);
-
-				tuple = heap_form_tuple(rsi->setDesc, values, nulls);
-				tuplestore_puttuple(rsi->setResult, tuple);
-			}
 		}
 	}
 
-- 
2.45.1