From a050f2d857b2e5321b9e1110f6a41185d91c51ee Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 22 Aug 2024 07:56:04 +0200
Subject: [PATCH v1] pg_upgrade: Support for upgrading to checksums enabled

When upgrading between instances with different checksum settings, the
--copy (default) mode automatically sets (or unsets) the checksum on
the fly.

TODO: What to do about the Windows code path?
---
 src/bin/pg_upgrade/controldata.c   | 17 +++++-----------
 src/bin/pg_upgrade/file.c          | 31 +++++++++++++++++++++++++++++-
 src/bin/pg_upgrade/pg_upgrade.h    |  3 ++-
 src/bin/pg_upgrade/relfilenumber.c |  2 +-
 4 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 854c6887a23..583cbf109cf 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -693,18 +693,11 @@ check_control_data(ControlData *oldctrl,
 	 * check_for_isn_and_int8_passing_mismatch().
 	 */
 
-	/*
-	 * We might eventually allow upgrades from checksum to no-checksum
-	 * clusters.
-	 */
-	if (oldctrl->data_checksum_version == 0 &&
-		newctrl->data_checksum_version != 0)
-		pg_fatal("old cluster does not use data checksums but the new one does");
-	else if (oldctrl->data_checksum_version != 0 &&
-			 newctrl->data_checksum_version == 0)
-		pg_fatal("old cluster uses data checksums but the new one does not");
-	else if (oldctrl->data_checksum_version != newctrl->data_checksum_version)
-		pg_fatal("old and new cluster pg_controldata checksum versions do not match");
+	if (oldctrl->data_checksum_version != newctrl->data_checksum_version)
+	{
+		if (user_opts.transfer_mode != TRANSFER_MODE_COPY)
+			pg_fatal("when upgrading between clusters with different data checksum settings, transfer mode --copy must be used");
+	}
 }
 
 
diff --git a/src/bin/pg_upgrade/file.c b/src/bin/pg_upgrade/file.c
index 73932504cae..0a16ad79237 100644
--- a/src/bin/pg_upgrade/file.c
+++ b/src/bin/pg_upgrade/file.c
@@ -80,12 +80,14 @@ cloneFile(const char *src, const char *dst,
  */
 void
 copyFile(const char *src, const char *dst,
-		 const char *schemaName, const char *relName)
+		 const char *schemaName, const char *relName,
+		 int segno)
 {
 #ifndef WIN32
 	int			src_fd;
 	int			dest_fd;
 	char	   *buffer;
+	BlockNumber blocknum;
 
 	if ((src_fd = open(src, O_RDONLY | PG_BINARY, 0)) < 0)
 		pg_fatal("error while copying relation \"%s.%s\": could not open file \"%s\": %m",
@@ -101,6 +103,8 @@ copyFile(const char *src, const char *dst,
 
 	buffer = (char *) pg_malloc(COPY_BUF_SIZE);
 
+	blocknum = segno * old_cluster.controldata.largesz;
+
 	/* perform data copying i.e read src source, write to destination */
 	while (true)
 	{
@@ -113,6 +117,31 @@ copyFile(const char *src, const char *dst,
 		if (nbytes == 0)
 			break;
 
+		/*
+		 * Update checksums if upgrading between different settings
+		 */
+		if (old_cluster.controldata.data_checksum_version != new_cluster.controldata.data_checksum_version)
+		{
+			/* must deal in whole blocks */
+			nbytes = nbytes / BLCKSZ * BLCKSZ;
+
+			for (int i = 0; i * BLCKSZ < nbytes; i++)
+			{
+				char	   *page = buffer + i * BLCKSZ;
+				PageHeader	header = (PageHeader) page;
+
+				if (PageIsNew(page))
+					continue;
+
+				if (new_cluster.controldata.data_checksum_version == 1)
+					header->pd_checksum = pg_checksum_page(page, blocknum);
+				else
+					header->pd_checksum = 0;
+
+				blocknum++;
+			}
+		}
+
 		errno = 0;
 		if (write(dest_fd, buffer, nbytes) != nbytes)
 		{
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index cdb6e2b7597..c6a4ade53a7 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -404,7 +404,8 @@ bool		pid_lock_file_exists(const char *datadir);
 void		cloneFile(const char *src, const char *dst,
 					  const char *schemaName, const char *relName);
 void		copyFile(const char *src, const char *dst,
-					 const char *schemaName, const char *relName);
+					 const char *schemaName, const char *relName,
+					 int segno);
 void		copyFileByRange(const char *src, const char *dst,
 							const char *schemaName, const char *relName);
 void		linkFile(const char *src, const char *dst,
diff --git a/src/bin/pg_upgrade/relfilenumber.c b/src/bin/pg_upgrade/relfilenumber.c
index 1d3054d78bd..2ae69d71159 100644
--- a/src/bin/pg_upgrade/relfilenumber.c
+++ b/src/bin/pg_upgrade/relfilenumber.c
@@ -250,7 +250,7 @@ transfer_relfile(FileNameMap *map, const char *type_suffix, bool vm_must_add_fro
 				case TRANSFER_MODE_COPY:
 					pg_log(PG_VERBOSE, "copying \"%s\" to \"%s\"",
 						   old_file, new_file);
-					copyFile(old_file, new_file, map->nspname, map->relname);
+					copyFile(old_file, new_file, map->nspname, map->relname, segno);
 					break;
 				case TRANSFER_MODE_COPY_FILE_RANGE:
 					pg_log(PG_VERBOSE, "copying \"%s\" to \"%s\" with copy_file_range",

base-commit: 9bb842f95ef3384f0822c386a4c569780e613e4e
-- 
2.46.0