4 * PostgreSQL transaction log internal declarations
6 * NOTE: this file is intended to contain declarations useful for
7 * manipulating the XLOG files directly, but it is not supposed to be
8 * needed by rmgr routines (redo support for individual record types).
9 * So the XLogRecord typedef and associated stuff appear in xlog.h.
11 * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
12 * Portions Copyright (c) 1994, Regents of the University of California
14 * src/include/access/xlog_internal.h
16 #ifndef XLOG_INTERNAL_H
17 #define XLOG_INTERNAL_H
19 #include "access/xlog.h"
20 #include "storage/block.h"
21 #include "storage/relfilenode.h"
25 * Header info for a backup block appended to an XLOG record.
27 * As a trivial form of data compression, the XLOG code is aware that
28 * PG data pages usually contain an unused "hole" in the middle, which
29 * contains only zero bytes. If hole_length > 0 then we have removed
30 * such a "hole" from the stored data (and it's not counted in the
31 * XLOG record's CRC, either). Hence, the amount of block data actually
32 * present following the BkpBlock struct is BLCKSZ - hole_length bytes.
34 * Note that we don't attempt to align either the BkpBlock struct or the
35 * block's data. So, the struct must be copied to aligned local storage
38 typedef struct BkpBlock
40 RelFileNode node; /* relation containing block */
41 ForkNumber fork; /* fork within the relation */
42 BlockNumber block; /* block number */
43 uint16 hole_offset; /* number of bytes before "hole" */
44 uint16 hole_length; /* number of bytes in "hole" */
46 /* ACTUAL BLOCK DATA FOLLOWS AT END OF STRUCT */
50 * When there is not enough space on current page for whole record, we
51 * continue on the next page with continuation record. (However, the
52 * XLogRecord header will never be split across pages; if there's less than
53 * SizeOfXLogRecord space left at the end of a page, we just waste it.)
55 * Note that xl_rem_len includes backup-block data; that is, it tracks
56 * xl_tot_len not xl_len in the initial header. Also note that the
57 * continuation data isn't necessarily aligned.
59 typedef struct XLogContRecord
61 uint32 xl_rem_len; /* total len of remaining data for record */
63 /* ACTUAL LOG DATA FOLLOWS AT END OF STRUCT */
67 #define SizeOfXLogContRecord sizeof(XLogContRecord)
70 * Each page of XLOG file has a header like this:
72 #define XLOG_PAGE_MAGIC 0xD068 /* can be used as WAL version indicator */
74 typedef struct XLogPageHeaderData
76 uint16 xlp_magic; /* magic value for correctness checks */
77 uint16 xlp_info; /* flag bits, see below */
78 TimeLineID xlp_tli; /* TimeLineID of first record on page */
79 XLogRecPtr xlp_pageaddr; /* XLOG address of this page */
82 #define SizeOfXLogShortPHD MAXALIGN(sizeof(XLogPageHeaderData))
84 typedef XLogPageHeaderData *XLogPageHeader;
87 * When the XLP_LONG_HEADER flag is set, we store additional fields in the
88 * page header. (This is ordinarily done just in the first page of an
89 * XLOG file.) The additional fields serve to identify the file accurately.
91 typedef struct XLogLongPageHeaderData
93 XLogPageHeaderData std; /* standard header fields */
94 uint64 xlp_sysid; /* system identifier from pg_control */
95 uint32 xlp_seg_size; /* just as a cross-check */
96 uint32 xlp_xlog_blcksz; /* just as a cross-check */
97 } XLogLongPageHeaderData;
99 #define SizeOfXLogLongPHD MAXALIGN(sizeof(XLogLongPageHeaderData))
101 typedef XLogLongPageHeaderData *XLogLongPageHeader;
103 /* When record crosses page boundary, set this flag in new page's header */
104 #define XLP_FIRST_IS_CONTRECORD 0x0001
105 /* This flag indicates a "long" page header */
106 #define XLP_LONG_HEADER 0x0002
107 /* All defined flag bits in xlp_info (used for validity checking of header) */
108 #define XLP_ALL_FLAGS 0x0003
110 #define XLogPageHeaderSize(hdr) \
111 (((hdr)->xlp_info & XLP_LONG_HEADER) ? SizeOfXLogLongPHD : SizeOfXLogShortPHD)
114 * We break each logical log file (xlogid value) into segment files of the
115 * size indicated by XLOG_SEG_SIZE. One possible segment at the end of each
116 * log file is wasted, to ensure that we don't have problems representing
117 * last-byte-position-plus-1.
119 #define XLogSegSize ((uint32) XLOG_SEG_SIZE)
120 #define XLogSegsPerFile (((uint32) 0xffffffff) / XLogSegSize)
121 #define XLogFileSize (XLogSegsPerFile * XLogSegSize)
125 * Macros for manipulating XLOG pointers
128 /* Increment an xlogid/segment pair */
129 #define NextLogSeg(logId, logSeg) \
131 if ((logSeg) >= XLogSegsPerFile-1) \
140 /* Decrement an xlogid/segment pair (assume it's not 0,0) */
141 #define PrevLogSeg(logId, logSeg) \
148 (logSeg) = XLogSegsPerFile-1; \
152 /* Align a record pointer to next page */
153 #define NextLogPage(recptr) \
155 if ((recptr).xrecoff % XLOG_BLCKSZ != 0) \
156 (recptr).xrecoff += \
157 (XLOG_BLCKSZ - (recptr).xrecoff % XLOG_BLCKSZ); \
158 if ((recptr).xrecoff >= XLogFileSize) \
160 ((recptr).xlogid)++; \
161 (recptr).xrecoff = 0; \
166 * Compute ID and segment from an XLogRecPtr.
168 * For XLByteToSeg, do the computation at face value. For XLByteToPrevSeg,
169 * a boundary byte is taken to be in the previous segment. This is suitable
170 * for deciding which segment to write given a pointer to a record end,
171 * for example. (We can assume xrecoff is not zero, since no valid recptr
174 #define XLByteToSeg(xlrp, logId, logSeg) \
175 ( logId = (xlrp).xlogid, \
176 logSeg = (xlrp).xrecoff / XLogSegSize \
178 #define XLByteToPrevSeg(xlrp, logId, logSeg) \
179 ( logId = (xlrp).xlogid, \
180 logSeg = ((xlrp).xrecoff - 1) / XLogSegSize \
184 * Is an XLogRecPtr within a particular XLOG segment?
186 * For XLByteInSeg, do the computation at face value. For XLByteInPrevSeg,
187 * a boundary byte is taken to be in the previous segment.
189 #define XLByteInSeg(xlrp, logId, logSeg) \
190 ((xlrp).xlogid == (logId) && \
191 (xlrp).xrecoff / XLogSegSize == (logSeg))
193 #define XLByteInPrevSeg(xlrp, logId, logSeg) \
194 ((xlrp).xlogid == (logId) && \
195 ((xlrp).xrecoff - 1) / XLogSegSize == (logSeg))
197 /* Check if an xrecoff value is in a plausible range */
198 #define XRecOffIsValid(xrecoff) \
199 ((xrecoff) % XLOG_BLCKSZ >= SizeOfXLogShortPHD && \
200 (XLOG_BLCKSZ - (xrecoff) % XLOG_BLCKSZ) >= SizeOfXLogRecord)
203 * The XLog directory and control file (relative to $PGDATA)
205 #define XLOGDIR "pg_xlog"
206 #define XLOG_CONTROL_FILE "global/pg_control"
209 * These macros encapsulate knowledge about the exact layout of XLog file
210 * names, timeline history file names, and archive-status file names.
212 #define MAXFNAMELEN 64
214 #define XLogFileName(fname, tli, log, seg) \
215 snprintf(fname, MAXFNAMELEN, "%08X%08X%08X", tli, log, seg)
217 #define XLogFromFileName(fname, tli, log, seg) \
218 sscanf(fname, "%08X%08X%08X", tli, log, seg)
220 #define XLogFilePath(path, tli, log, seg) \
221 snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X", tli, log, seg)
223 #define TLHistoryFileName(fname, tli) \
224 snprintf(fname, MAXFNAMELEN, "%08X.history", tli)
226 #define TLHistoryFilePath(path, tli) \
227 snprintf(path, MAXPGPATH, XLOGDIR "/%08X.history", tli)
229 #define StatusFilePath(path, xlog, suffix) \
230 snprintf(path, MAXPGPATH, XLOGDIR "/archive_status/%s%s", xlog, suffix)
232 #define BackupHistoryFileName(fname, tli, log, seg, offset) \
233 snprintf(fname, MAXFNAMELEN, "%08X%08X%08X.%08X.backup", tli, log, seg, offset)
235 #define BackupHistoryFilePath(path, tli, log, seg, offset) \
236 snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X.%08X.backup", tli, log, seg, offset)
240 * Method table for resource managers.
242 * RmgrTable[] is indexed by RmgrId values (see rmgr.h).
244 typedef struct RmgrData
247 void (*rm_redo) (XLogRecPtr lsn, XLogRecord *rptr);
248 void (*rm_desc) (StringInfo buf, uint8 xl_info, char *rec);
249 void (*rm_startup) (void);
250 void (*rm_cleanup) (void);
251 bool (*rm_safe_restartpoint) (void);
254 extern const RmgrData RmgrTable[];
257 * Exported to support xlog switching from bgwriter
259 extern pg_time_t GetLastSegSwitchTime(void);
260 extern XLogRecPtr RequestXLogSwitch(void);
263 * These aren't in xlog.h because I'd rather not include fmgr.h there.
265 extern Datum pg_start_backup(PG_FUNCTION_ARGS);
266 extern Datum pg_stop_backup(PG_FUNCTION_ARGS);
267 extern Datum pg_switch_xlog(PG_FUNCTION_ARGS);
268 extern Datum pg_create_restore_point(PG_FUNCTION_ARGS);
269 extern Datum pg_current_xlog_location(PG_FUNCTION_ARGS);
270 extern Datum pg_current_xlog_insert_location(PG_FUNCTION_ARGS);
271 extern Datum pg_last_xlog_receive_location(PG_FUNCTION_ARGS);
272 extern Datum pg_last_xlog_replay_location(PG_FUNCTION_ARGS);
273 extern Datum pg_last_xact_replay_timestamp(PG_FUNCTION_ARGS);
274 extern Datum pg_xlogfile_name_offset(PG_FUNCTION_ARGS);
275 extern Datum pg_xlogfile_name(PG_FUNCTION_ARGS);
276 extern Datum pg_is_in_recovery(PG_FUNCTION_ARGS);
277 extern Datum pg_xlog_replay_pause(PG_FUNCTION_ARGS);
278 extern Datum pg_xlog_replay_resume(PG_FUNCTION_ARGS);
279 extern Datum pg_is_xlog_replay_paused(PG_FUNCTION_ARGS);
281 #endif /* XLOG_INTERNAL_H */