read block via pg_ptrack_read_block() for every page in ptrack backups and every invalid page in other backup modes

src/backup.c

@@ -2694,3 +2694,45 @@ get_last_ptrack_lsn(void)
 	PQclear(res);
 	return lsn;
 }
+
+char *
+pg_ptrack_get_block(Oid relOid,
+					BlockNumber blknum,
+					size_t *result_size)
+{
+	PGresult   *res;
+	char	   *params[2];
+	char	   *result;
+	char	   *val;
+
+	params[0] = palloc(64);
+	params[1] = palloc(64);
+
+	/*
+	 * Use backup_conn, cause we can do it from any database.
+	 */
+	sprintf(params[0], "%i", relOid);
+	sprintf(params[1], "%u", blknum);
+	res = pgut_execute(backup_conn, "SELECT pg_ptrack_get_block($1, $2)",
+					2, (const char **)params, true);
+
+	if (PQnfields(res) != 1)
+		elog(WARNING, "cannot get file block for relation oid %u",
+		relOid);
+
+	val = PQgetvalue(res, 0, 0);
+
+	if (strcmp("x", val+1) == 0)
+	{
+		/* Ptrack file is missing */
+		return NULL;
+	}
+
+	result = (char *) PQunescapeBytea((unsigned char *) PQgetvalue(res, 0, 0),
+									  result_size);
+	PQclear(res);
+	pfree(params[0]);
+	pfree(params[1]);
+
+	return result;
+}

src/data.c

@@ -121,11 +121,13 @@ static void
 backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 				 BlockNumber blknum, BlockNumber nblocks,
 				 FILE *in, FILE *out,
-				 pg_crc32 *crc, int *n_skipped)
+				 pg_crc32 *crc, int *n_skipped,
+				 BackupMode backup_mode)
 {
 	BackupPageHeader	header;
 	off_t				offset;
 	DataPage			page; /* used as read buffer */
+	DataPage			*page_ptr = &page; /* used as read buffer */
 	DataPage			compressed_page; /* used as read buffer */
 	size_t				write_buffer_size;
 	/* maximum size of write buffer */
@@ -133,7 +135,7 @@ backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 	size_t				read_len = 0;
 	XLogRecPtr			page_lsn;
 	int					try_checksum = 100;
-
+	bool				page_is_invalid = true;
 	header.block = blknum;
 	offset = blknum * BLCKSZ;
 
@@ -156,6 +158,7 @@ backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 			{
 				elog(LOG, "File %s, block %u, file was truncated",
 					 file->path, blknum);
+				page_is_invalid = false;
 				return;
 			}
 			else if (try_checksum)
@@ -187,6 +190,7 @@ backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 			if (i == BLCKSZ)
 			{
 				elog(LOG, "File: %s blknum %u, empty page", file->path, blknum);
+				page_is_invalid = false;
 				break;
 			}
 
@@ -238,10 +242,24 @@ backup_data_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 									file->path, blknum);
 			}
 			else
+			{
+				page_is_invalid = false;
 				break; /* page header and checksum are correct */
+			}
 		}
 		else
+		{
+			page_is_invalid = false;
 			break; /* page header is correct and checksum check is disabled */
+		}
+	}
+
+
+	if (page_is_invalid ||
+		(backup_mode == BACKUP_MODE_DIFF_PTRACK))
+	{
+		size_t page_size = 0;
+		page_ptr = pg_ptrack_get_block(file->relOid, blknum, &page_size);
 	}
 
 	file->read_size += read_len;
@@ -388,7 +406,8 @@ backup_data_file(const char *from_root, const char *to_root,
 		for (blknum = 0; blknum < nblocks; blknum++)
 		{
 			backup_data_page(file, prev_backup_start_lsn, blknum,
-							 nblocks, in, out, &(file->crc), &n_blocks_skipped);
+							 nblocks, in, out, &(file->crc),
+							 &n_blocks_skipped, backup_mode);
 			n_blocks_read++;
 		}
 	}
@@ -400,7 +419,8 @@ backup_data_file(const char *from_root, const char *to_root,
 		while (datapagemap_next(iter, &blknum))
 		{
 			backup_data_page(file, prev_backup_start_lsn, blknum,
-							 nblocks, in, out, &(file->crc), &n_blocks_skipped);
+							 nblocks, in, out, &(file->crc),
+							 &n_blocks_skipped, backup_mode);
 			n_blocks_read++;
 		}
 

src/pg_probackup.h

@@ -320,6 +320,8 @@ extern bool fileExists(const char *path);
 extern void process_block_change(ForkNumber forknum, RelFileNode rnode,
 								 BlockNumber blkno);
 
+extern char *pg_ptrack_get_block(Oid relOid, BlockNumber blknum,
+								 size_t *result_size);
 /* in restore.c */
 extern int do_restore_or_validate(time_t target_backup_id,
 					  const char *target_time,