Change how a base backup decides which files have checksums.

Previously, it thought that any plain file located under global, base,
or a tablespace directory had checksums unless it was in a short list
of excluded files. Now, it thinks that files in those directories have
checksums if parse_filename_for_nontemp_relation says that they are
relation files. (Temporary relation files don't matter because they're
excluded from the backup anyway.)

This changes the behavior if you have stray files not managed by
PostgreSQL in the relevant directories. Previously, you'd get some
kind of checksum-related complaint if such files existed, assuming
that the cluster had checksums enabled and that the base backup
wasn't run with NOVERIFY_CHECKSUMS. Now, you won't get those
complaints any more. That seems like an improvement to me, because
those files were presumably not created by PostgreSQL and so there
is no reason to think that they would be checksummed like a
PostgreSQL relation file. (If we want to complain about such files,
we should complain about them existing at all, not just about their
checksums.)

The point of this change is to make the code more consistent.
sendDir() was already calling parse_filename_for_nontemp_relation()
as part of an effort to determine which files to include in the
backup. So, it already had the information about whether a certain
file was a relation file. sendFile() then used a separate method,
embodied in is_checksummed_file(), to make what is essentially
the same determination. It's better not to make the same decision
using two different methods, especially in closely-related code.

Patch by me. Reviewed by Dilip Kumar and Álvaro Herrera. Thanks
also to Jakub Wartak and Peter Eisentraut for comments, suggestions,
and testing on the larger patch set of which this is a part.

Discussion: http://postgr.es/m/CAFiTN-snhaKkWhi2Gz5i3cZeKefun6sYL==wBoqqnTXxX4_mFA@mail.gmail.com
Discussion: http://postgr.es/m/202311141312.u4qx5gtpvfq3@alvherre.pgsql

Author: robertmhaas

src/backend/backup/basebackup.c

@@ -82,7 +82,8 @@ static int64 sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeo
 					 backup_manifest_info *manifest, Oid spcoid);
 static bool sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
 					 struct stat *statbuf, bool missing_ok,
-					 Oid dboid, Oid spcoid,
+					 Oid dboid, Oid spcoid, RelFileNumber relfilenumber,
+					 unsigned segno,
 					 backup_manifest_info *manifest);
 static off_t read_file_data_into_buffer(bbsink *sink,
 										const char *readfilename, int fd,
@@ -104,7 +105,6 @@ static void convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
 static void perform_base_backup(basebackup_options *opt, bbsink *sink);
 static void parse_basebackup_options(List *options, basebackup_options *opt);
 static int	compareWalFileNames(const ListCell *a, const ListCell *b);
-static bool is_checksummed_file(const char *fullpath, const char *filename);
 static int	basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
 								 const char *filename, bool partial_read_ok);
 
@@ -213,23 +213,6 @@ static const struct exclude_list_item excludeFiles[] =
 	{NULL, false}
 };
 
-/*
- * List of files excluded from checksum validation.
- *
- * Note: this list should be kept in sync with what pg_checksums.c
- * includes.
- */
-static const struct exclude_list_item noChecksumFiles[] = {
-	{"pg_control", false},
-	{"pg_filenode.map", false},
-	{"pg_internal.init", true},
-	{"PG_VERSION", false},
-#ifdef EXEC_BACKEND
-	{"config_exec_params", true},
-#endif
-	{NULL, false}
-};
-
 /*
  * Actually do a base backup for the specified tablespaces.
  *
@@ -356,7 +339,8 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 							 errmsg("could not stat file \"%s\": %m",
 									XLOG_CONTROL_FILE)));
 				sendFile(sink, XLOG_CONTROL_FILE, XLOG_CONTROL_FILE, &statbuf,
-						 false, InvalidOid, InvalidOid, &manifest);
+						 false, InvalidOid, InvalidOid,
+						 InvalidRelFileNumber, 0, &manifest);
 			}
 			else
 			{
@@ -625,7 +609,8 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 						 errmsg("could not stat file \"%s\": %m", pathbuf)));
 
 			sendFile(sink, pathbuf, pathbuf, &statbuf, false,
-					 InvalidOid, InvalidOid, &manifest);
+					 InvalidOid, InvalidOid, InvalidRelFileNumber, 0,
+					 &manifest);
 
 			/* unconditionally mark file as archived */
 			StatusFilePath(pathbuf, fname, ".done");
@@ -1166,7 +1151,8 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 	struct stat statbuf;
 	int64		size = 0;
 	const char *lastDir;		/* Split last dir from parent path. */
-	bool		isDbDir = false;	/* Does this directory contain relations? */
+	bool		isRelationDir = false;	/* Does directory contain relations? */
+	Oid			dboid = InvalidOid;
 
 	/*
 	 * Determine if the current path is a database directory that can contain
@@ -1193,17 +1179,23 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 			 strncmp(lastDir - (sizeof(TABLESPACE_VERSION_DIRECTORY) - 1),
 					 TABLESPACE_VERSION_DIRECTORY,
 					 sizeof(TABLESPACE_VERSION_DIRECTORY) - 1) == 0))
-			isDbDir = true;
+		{
+			isRelationDir = true;
+			dboid = atooid(lastDir + 1);
+		}
 	}
+	else if (strcmp(path, "./global") == 0)
+		isRelationDir = true;
 
 	dir = AllocateDir(path);
 	while ((de = ReadDir(dir, path)) != NULL)
 	{
 		int			excludeIdx;
 		bool		excludeFound;
-		RelFileNumber relNumber;
-		ForkNumber	relForkNum;
-		unsigned	segno;
+		RelFileNumber relfilenumber = InvalidRelFileNumber;
+		ForkNumber	relForkNum = InvalidForkNumber;
+		unsigned	segno = 0;
+		bool		isRelationFile = false;
 
 		/* Skip special stuff */
 		if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
@@ -1251,37 +1243,40 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		if (excludeFound)
 			continue;
 
+		/*
+		 * If there could be non-temporary relation files in this directory,
+		 * try to parse the filename.
+		 */
+		if (isRelationDir)
+			isRelationFile =
+				parse_filename_for_nontemp_relation(de->d_name,
+													&relfilenumber,
+													&relForkNum, &segno);
+
 		/* Exclude all forks for unlogged tables except the init fork */
-		if (isDbDir &&
-			parse_filename_for_nontemp_relation(de->d_name, &relNumber,
-												&relForkNum, &segno))
+		if (isRelationFile && relForkNum != INIT_FORKNUM)
 		{
-			/* Never exclude init forks */
-			if (relForkNum != INIT_FORKNUM)
-			{
-				char		initForkFile[MAXPGPATH];
+			char		initForkFile[MAXPGPATH];
 
-				/*
-				 * If any other type of fork, check if there is an init fork
-				 * with the same RelFileNumber. If so, the file can be
-				 * excluded.
-				 */
-				snprintf(initForkFile, sizeof(initForkFile), "%s/%u_init",
-						 path, relNumber);
+			/*
+			 * If any other type of fork, check if there is an init fork with
+			 * the same RelFileNumber. If so, the file can be excluded.
+			 */
+			snprintf(initForkFile, sizeof(initForkFile), "%s/%u_init",
+					 path, relfilenumber);
 
-				if (lstat(initForkFile, &statbuf) == 0)
-				{
-					elog(DEBUG2,
-						 "unlogged relation file \"%s\" excluded from backup",
-						 de->d_name);
+			if (lstat(initForkFile, &statbuf) == 0)
+			{
+				elog(DEBUG2,
+					 "unlogged relation file \"%s\" excluded from backup",
+					 de->d_name);
 
-					continue;
-				}
+				continue;
 			}
 		}
 
 		/* Exclude temporary relations */
-		if (isDbDir && looks_like_temp_rel_name(de->d_name))
+		if (OidIsValid(dboid) && looks_like_temp_rel_name(de->d_name))
 		{
 			elog(DEBUG2,
 				 "temporary relation file \"%s\" excluded from backup",
@@ -1420,8 +1415,8 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 
 			if (!sizeonly)
 				sent = sendFile(sink, pathbuf, pathbuf + basepathlen + 1, &statbuf,
-								true, isDbDir ? atooid(lastDir + 1) : InvalidOid, spcoid,
-								manifest);
+								true, dboid, spcoid,
+								relfilenumber, segno, manifest);
 
 			if (sent || sizeonly)
 			{
@@ -1443,40 +1438,6 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 	return size;
 }
 
-/*
- * Check if a file should have its checksum validated.
- * We validate checksums on files in regular tablespaces
- * (including global and default) only, and in those there
- * are some files that are explicitly excluded.
- */
-static bool
-is_checksummed_file(const char *fullpath, const char *filename)
-{
-	/* Check that the file is in a tablespace */
-	if (strncmp(fullpath, "./global/", 9) == 0 ||
-		strncmp(fullpath, "./base/", 7) == 0 ||
-		strncmp(fullpath, "/", 1) == 0)
-	{
-		int			excludeIdx;
-
-		/* Compare file against noChecksumFiles skip list */
-		for (excludeIdx = 0; noChecksumFiles[excludeIdx].name != NULL; excludeIdx++)
-		{
-			int			cmplen = strlen(noChecksumFiles[excludeIdx].name);
-
-			if (!noChecksumFiles[excludeIdx].match_prefix)
-				cmplen++;
-			if (strncmp(filename, noChecksumFiles[excludeIdx].name,
-						cmplen) == 0)
-				return false;
-		}
-
-		return true;
-	}
-	else
-		return false;
-}
-
 /*
  * Given the member, write the TAR header & send the file.
  *
@@ -1491,15 +1452,14 @@ is_checksummed_file(const char *fullpath, const char *filename)
 static bool
 sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
 		 struct stat *statbuf, bool missing_ok, Oid dboid, Oid spcoid,
+		 RelFileNumber relfilenumber, unsigned segno,
 		 backup_manifest_info *manifest)
 {
 	int			fd;
 	BlockNumber blkno = 0;
 	int			checksum_failures = 0;
 	off_t		cnt;
 	pgoff_t		bytes_done = 0;
-	int			segmentno = 0;
-	char	   *segmentpath;
 	bool		verify_checksum = false;
 	pg_checksum_context checksum_ctx;
 
@@ -1525,36 +1485,14 @@ sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
 	 */
 	Assert((sink->bbs_buffer_length % BLCKSZ) == 0);
 
-	if (!noverify_checksums && DataChecksumsEnabled())
-	{
-		char	   *filename;
-
-		/*
-		 * Get the filename (excluding path).  As last_dir_separator()
-		 * includes the last directory separator, we chop that off by
-		 * incrementing the pointer.
-		 */
-		filename = last_dir_separator(readfilename) + 1;
-
-		if (is_checksummed_file(readfilename, filename))
-		{
-			verify_checksum = true;
-
-			/*
-			 * Cut off at the segment boundary (".") to get the segment number
-			 * in order to mix it into the checksum.
-			 */
-			segmentpath = strstr(filename, ".");
-			if (segmentpath != NULL)
-			{
-				segmentno = atoi(segmentpath + 1);
-				if (segmentno == 0)
-					ereport(ERROR,
-							(errmsg("invalid segment number %d in file \"%s\"",
-									segmentno, filename)));
-			}
-		}
-	}
+	/*
+	 * If we weren't told not to verify checksums, and if checksums are
+	 * enabled for this cluster, and if this is a relation file, then verify
+	 * the checksum.
+	 */
+	if (!noverify_checksums && DataChecksumsEnabled() &&
+		RelFileNumberIsValid(relfilenumber))
+		verify_checksum = true;
 
 	/*
 	 * Loop until we read the amount of data the caller told us to expect. The
@@ -1569,7 +1507,7 @@ sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
 		/* Try to read some more data. */
 		cnt = read_file_data_into_buffer(sink, readfilename, fd, bytes_done,
 										 remaining,
-										 blkno + segmentno * RELSEG_SIZE,
+										 blkno + segno * RELSEG_SIZE,
 										 verify_checksum,
 										 &checksum_failures);