fix databaseOID usage for pg_ptrack_get_block()

Author: alubennikova

src/backup.c

@@ -2668,29 +2668,59 @@ get_last_ptrack_lsn(void)
 }
 
 char *
-pg_ptrack_get_block(Oid tblsOid,
+pg_ptrack_get_block(Oid dbOid,
+					Oid tblsOid,
 					Oid relOid,
 					BlockNumber blknum,
 					size_t *result_size)
 {
+	PGresult   *res_db;
 	PGresult   *res;
+	const char *dbname;
 	char	   *params[3];
 	char	   *result;
 	char	   *val;
+	PGconn	   *tmp_conn;
 
 	params[0] = palloc(64);
 	params[1] = palloc(64);
 	params[2] = palloc(64);
 
+	sprintf(params[0], "%i", dbOid);
+	res_db = pgut_execute(backup_conn,
+							"SELECT datname FROM pg_database WHERE oid=$1",
+							1, (const char **) params, true);
+	/*
+	 * If database is not found, it's not an error.
+	 * It could have been deleted.
+	 */
+	if (PQntuples(res_db) != 1 || PQnfields(res_db) != 1)
+	{
+		//elog(LOG, "Database with oid %d is not found", dbOid);
+		return NULL;
+	}
+
+	dbname = PQgetvalue(res_db, 0, 0);
+	if (strcmp(dbname, "template0") == 0)
+	{
+		/*
+		 * There is no way to connect to the template0 database.
+		 * But it's totally OK, since files there can never be changed.
+		 */
+		return NULL;
+	}
+	tmp_conn = pgut_connect(dbname);
+
 	/*
 	 * Use backup_conn, cause we can do it from any database.
 	 */
 	sprintf(params[0], "%i", tblsOid);
 	sprintf(params[1], "%i", relOid);
 	sprintf(params[2], "%u", blknum);
 
-// 	elog(WARNING, "pg_ptrack_get_block(%i, %i, %u)", tblsOid, relOid, blknum);
-	res = pgut_execute(backup_conn, "SELECT pg_ptrack_get_block($1, $2, $3)",
+	//elog(WARNING, "db %i pg_ptrack_get_block(%i, %i, %u)",dbOid, tblsOid, relOid, blknum);
+
+	res = pgut_execute(tmp_conn, "SELECT pg_ptrack_get_block($1, $2, $3)",
 					3, (const char **)params, true);
 
 	if (PQnfields(res) != 1)
@@ -2704,7 +2734,10 @@ pg_ptrack_get_block(Oid tblsOid,
 
 	result = (char *) PQunescapeBytea((unsigned char *) PQgetvalue(res, 0, 0),
 									  result_size);
+
+	pgut_disconnect(tmp_conn);
 	PQclear(res);
+	PQclear(res_db);
 	pfree(params[0]);
 	pfree(params[1]);
 	pfree(params[2]);

src/data.c

@@ -268,13 +268,15 @@ backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 
 		free(page);
 		page = NULL;
-
-		page = (Page) pg_ptrack_get_block(file->tblspcOid, file->relOid, absolute_blknum, &page_size);
+		page = (Page) pg_ptrack_get_block(file->dbOid, file->tblspcOid,
+										  file->relOid, absolute_blknum, &page_size);
 
 		if (page == NULL)
 		{
-			elog(WARNING, "File %s, block %u, file was truncated",
-					file->path, absolute_blknum);
+			/*
+			 * We may skip block for various reasons. It's fine.
+			 * Otherwise pg_ptrack_get_block would have failed with ERROR.
+			 */
 			return;
 		}
 

src/pg_probackup.h

@@ -320,7 +320,7 @@ extern const char *deparse_backup_mode(BackupMode mode);
 extern void process_block_change(ForkNumber forknum, RelFileNode rnode,
 								 BlockNumber blkno);
 
-extern char *pg_ptrack_get_block(Oid tblsOid, Oid relOid, BlockNumber blknum,
+extern char *pg_ptrack_get_block(Oid dbOid, Oid tblsOid, Oid relOid, BlockNumber blknum,
 								 size_t *result_size);
 /* in restore.c */
 extern int do_restore_or_validate(time_t target_backup_id,