pg_verifybackup: Refactor parse_manifest_file.

Return a pointer to the manifest_data instead of individual pointers
to relevant data stored within the manifest_data object. The previous
approach scales poorly if we add more things to the backup manifest,
as has been proposed.

Amul Sul, reviewed by Sravan Velagandula, Michael Paquier, and me.

Discussion: http://postgr.es/m/CAAJ_b95=1LONf99-M_ep588fL_WgLJfdnb7XG4GWE7JDD22E4w@mail.gmail.com

Author: robertmhaas

src/bin/pg_verifybackup/pg_verifybackup.c

@@ -94,31 +94,28 @@ typedef struct manifest_wal_range
 } manifest_wal_range;
 
 /*
- * Details we need in callbacks that occur while parsing a backup manifest.
+ * All the data parsed from a backup_manifest file.
  */
-typedef struct parser_context
+typedef struct manifest_data
 {
-	manifest_files_hash *ht;
+	manifest_files_hash *files;
 	manifest_wal_range *first_wal_range;
 	manifest_wal_range *last_wal_range;
-} parser_context;
+} manifest_data;
 
 /*
  * All of the context information we need while checking a backup manifest.
  */
 typedef struct verifier_context
 {
-	manifest_files_hash *ht;
+	manifest_data *manifest;
 	char	   *backup_directory;
 	SimpleStringList ignore_list;
 	bool		exit_on_error;
 	bool		saw_any_error;
 } verifier_context;
 
-static void parse_manifest_file(char *manifest_path,
-								manifest_files_hash **ht_p,
-								manifest_wal_range **first_wal_range_p);
-
+static manifest_data *parse_manifest_file(char *manifest_path);
 static void verifybackup_per_file_cb(JsonManifestParseContext *context,
 									 char *pathname, size_t size,
 									 pg_checksum_type checksum_type,
@@ -142,8 +139,7 @@ static void verify_file_checksum(verifier_context *context,
 								 manifest_file *m, char *fullpath);
 static void parse_required_wal(verifier_context *context,
 							   char *pg_waldump_path,
-							   char *wal_directory,
-							   manifest_wal_range *first_wal_range);
+							   char *wal_directory);
 
 static void report_backup_error(verifier_context *context,
 								const char *pg_restrict fmt,...)
@@ -185,7 +181,6 @@ main(int argc, char **argv)
 
 	int			c;
 	verifier_context context;
-	manifest_wal_range *first_wal_range;
 	char	   *manifest_path = NULL;
 	bool		no_parse_wal = false;
 	bool		quiet = false;
@@ -338,7 +333,7 @@ main(int argc, char **argv)
 	 * the manifest as fatal; there doesn't seem to be much point in trying to
 	 * verify the backup directory against a corrupted manifest.
 	 */
-	parse_manifest_file(manifest_path, &context.ht, &first_wal_range);
+	context.manifest = parse_manifest_file(manifest_path);
 
 	/*
 	 * Now scan the files in the backup directory. At this stage, we verify
@@ -367,8 +362,7 @@ main(int argc, char **argv)
 	 * not to do so.
 	 */
 	if (!no_parse_wal)
-		parse_required_wal(&context, pg_waldump_path,
-						   wal_directory, first_wal_range);
+		parse_required_wal(&context, pg_waldump_path, wal_directory);
 
 	/*
 	 * If everything looks OK, tell the user this, unless we were asked to
@@ -385,9 +379,8 @@ main(int argc, char **argv)
  * all the files it mentions, and a linked list of all the WAL ranges it
  * mentions.
  */
-static void
-parse_manifest_file(char *manifest_path, manifest_files_hash **ht_p,
-					manifest_wal_range **first_wal_range_p)
+static manifest_data *
+parse_manifest_file(char *manifest_path)
 {
 	int			fd;
 	struct stat statbuf;
@@ -396,8 +389,8 @@ parse_manifest_file(char *manifest_path, manifest_files_hash **ht_p,
 	manifest_files_hash *ht;
 	char	   *buffer;
 	int			rc;
-	parser_context private_context;
 	JsonManifestParseContext context;
+	manifest_data *result;
 
 	/* Open the manifest file. */
 	if ((fd = open(manifest_path, O_RDONLY | PG_BINARY, 0)) < 0)
@@ -436,10 +429,9 @@ parse_manifest_file(char *manifest_path, manifest_files_hash **ht_p,
 	close(fd);
 
 	/* Parse the manifest. */
-	private_context.ht = ht;
-	private_context.first_wal_range = NULL;
-	private_context.last_wal_range = NULL;
-	context.private_data = &private_context;
+	result = pg_malloc0(sizeof(manifest_data));
+	result->files = ht;
+	context.private_data = result;
 	context.per_file_cb = verifybackup_per_file_cb;
 	context.per_wal_range_cb = verifybackup_per_wal_range_cb;
 	context.error_cb = report_manifest_error;
@@ -448,9 +440,7 @@ parse_manifest_file(char *manifest_path, manifest_files_hash **ht_p,
 	/* Done with the buffer. */
 	pfree(buffer);
 
-	/* Return the file hash table and WAL range list we constructed. */
-	*ht_p = ht;
-	*first_wal_range_p = private_context.first_wal_range;
+	return result;
 }
 
 /*
@@ -480,8 +470,8 @@ verifybackup_per_file_cb(JsonManifestParseContext *context,
 						 pg_checksum_type checksum_type,
 						 int checksum_length, uint8 *checksum_payload)
 {
-	parser_context *pcxt = context->private_data;
-	manifest_files_hash *ht = pcxt->ht;
+	manifest_data *manifest = context->private_data;
+	manifest_files_hash *ht = manifest->files;
 	manifest_file *m;
 	bool		found;
 
@@ -508,23 +498,23 @@ verifybackup_per_wal_range_cb(JsonManifestParseContext *context,
 							  TimeLineID tli,
 							  XLogRecPtr start_lsn, XLogRecPtr end_lsn)
 {
-	parser_context *pcxt = context->private_data;
+	manifest_data *manifest = context->private_data;
 	manifest_wal_range *range;
 
 	/* Allocate and initialize a struct describing this WAL range. */
 	range = palloc(sizeof(manifest_wal_range));
 	range->tli = tli;
 	range->start_lsn = start_lsn;
 	range->end_lsn = end_lsn;
-	range->prev = pcxt->last_wal_range;
+	range->prev = manifest->last_wal_range;
 	range->next = NULL;
 
 	/* Add it to the end of the list. */
-	if (pcxt->first_wal_range == NULL)
-		pcxt->first_wal_range = range;
+	if (manifest->first_wal_range == NULL)
+		manifest->first_wal_range = range;
 	else
-		pcxt->last_wal_range->next = range;
-	pcxt->last_wal_range = range;
+		manifest->last_wal_range->next = range;
+	manifest->last_wal_range = range;
 }
 
 /*
@@ -639,7 +629,7 @@ verify_backup_file(verifier_context *context, char *relpath, char *fullpath)
 	}
 
 	/* Check whether there's an entry in the manifest hash. */
-	m = manifest_files_lookup(context->ht, relpath);
+	m = manifest_files_lookup(context->manifest->files, relpath);
 	if (m == NULL)
 	{
 		report_backup_error(context,
@@ -679,11 +669,12 @@ verify_backup_file(verifier_context *context, char *relpath, char *fullpath)
 static void
 report_extra_backup_files(verifier_context *context)
 {
+	manifest_data *manifest = context->manifest;
 	manifest_files_iterator it;
 	manifest_file *m;
 
-	manifest_files_start_iterate(context->ht, &it);
-	while ((m = manifest_files_iterate(context->ht, &it)) != NULL)
+	manifest_files_start_iterate(manifest->files, &it);
+	while ((m = manifest_files_iterate(manifest->files, &it)) != NULL)
 		if (!m->matched && !should_ignore_relpath(context, m->pathname))
 			report_backup_error(context,
 								"\"%s\" is present in the manifest but not on disk",
@@ -698,13 +689,14 @@ report_extra_backup_files(verifier_context *context)
 static void
 verify_backup_checksums(verifier_context *context)
 {
+	manifest_data *manifest = context->manifest;
 	manifest_files_iterator it;
 	manifest_file *m;
 
 	progress_report(false);
 
-	manifest_files_start_iterate(context->ht, &it);
-	while ((m = manifest_files_iterate(context->ht, &it)) != NULL)
+	manifest_files_start_iterate(manifest->files, &it);
+	while ((m = manifest_files_iterate(manifest->files, &it)) != NULL)
 	{
 		if (should_verify_checksum(m) &&
 			!should_ignore_relpath(context, m->pathname))
@@ -833,9 +825,10 @@ verify_file_checksum(verifier_context *context, manifest_file *m,
  */
 static void
 parse_required_wal(verifier_context *context, char *pg_waldump_path,
-				   char *wal_directory, manifest_wal_range *first_wal_range)
+				   char *wal_directory)
 {
-	manifest_wal_range *this_wal_range = first_wal_range;
+	manifest_data *manifest = context->manifest;
+	manifest_wal_range *this_wal_range = manifest->first_wal_range;
 
 	while (this_wal_range != NULL)
 	{