diff options
Diffstat (limited to 'src/include/access/xlog.h')
| -rw-r--r-- | src/include/access/xlog.h | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index ab471738970..1d1aa9c1526 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -6,7 +6,7 @@ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.61 2005/05/20 14:53:26 momjian Exp $ + * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.62 2005/06/02 05:55:29 tgl Exp $ */ #ifndef XLOG_H #define XLOG_H @@ -19,23 +19,31 @@ /* - * Header for each record in XLOG + * The overall layout of an XLOG record is: + * Fixed-size header (XLogRecord struct) + * rmgr-specific data + * BkpBlock + * backup block data + * BkpBlock + * backup block data + * ... * - * NOTE: xl_len counts only the rmgr data, not the XLogRecord header, - * and also not any backup blocks appended to the record (which are signaled - * by xl_info flag bits). The total space needed for an XLOG record is - * really: - * - * SizeOfXLogRecord + xl_len + n_backup_blocks * (sizeof(BkpBlock) + BLCKSZ) + * where there can be zero to three backup blocks (as signaled by xl_info flag + * bits). XLogRecord structs always start on MAXALIGN boundaries in the WAL + * files, and we round up SizeOfXLogRecord so that the rmgr data is also + * guaranteed to begin on a MAXALIGN boundary. However, no padding is added + * to align BkpBlock structs or backup block data. * - * rounded up to a MAXALIGN boundary (so that all xlog records start on - * MAXALIGN boundaries). + * NOTE: xl_len counts only the rmgr data, not the XLogRecord header, + * and also not any backup blocks. xl_tot_len counts everything. Neither + * length field is rounded up to an alignment boundary. */ typedef struct XLogRecord { - crc64 xl_crc; /* CRC for this record */ + pg_crc32 xl_crc; /* CRC for this record */ XLogRecPtr xl_prev; /* ptr to previous record in log */ TransactionId xl_xid; /* xact id */ + uint32 xl_tot_len; /* total len of entire record */ uint32 xl_len; /* total len of rmgr data */ uint8 xl_info; /* flag bits, see below */ RmgrId xl_rmid; /* resource manager for this record */ |