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) 1996-2010, PostgreSQL Global Development Group
12 * Portions Copyright (c) 1994, Regents of the University of California
14 * $PostgreSQL: pgsql/src/include/access/xlog_internal.h,v 1.28 2010/01/15 09:19:06 heikki Exp $
16 #ifndef XLOG_INTERNAL_H
17 #define XLOG_INTERNAL_H
19 #include "access/xlog.h"
22 #include "storage/block.h"
23 #include "storage/relfilenode.h"
27 * Header info for a backup block appended to an XLOG record.
29 * As a trivial form of data compression, the XLOG code is aware that
30 * PG data pages usually contain an unused "hole" in the middle, which
31 * contains only zero bytes. If hole_length > 0 then we have removed
32 * such a "hole" from the stored data (and it's not counted in the
33 * XLOG record's CRC, either). Hence, the amount of block data actually
34 * present following the BkpBlock struct is BLCKSZ - hole_length bytes.
36 * Note that we don't attempt to align either the BkpBlock struct or the
37 * block's data. So, the struct must be copied to aligned local storage
40 typedef struct BkpBlock
42 RelFileNode node; /* relation containing block */
43 ForkNumber fork; /* fork within the relation */
44 BlockNumber block; /* block number */
45 uint16 hole_offset; /* number of bytes before "hole" */
46 uint16 hole_length; /* number of bytes in "hole" */
48 /* ACTUAL BLOCK DATA FOLLOWS AT END OF STRUCT */
52 * When there is not enough space on current page for whole record, we
53 * continue on the next page with continuation record. (However, the
54 * XLogRecord header will never be split across pages; if there's less than
55 * SizeOfXLogRecord space left at the end of a page, we just waste it.)
57 * Note that xl_rem_len includes backup-block data; that is, it tracks
58 * xl_tot_len not xl_len in the initial header. Also note that the
59 * continuation data isn't necessarily aligned.
61 typedef struct XLogContRecord
63 uint32 xl_rem_len; /* total len of remaining data for record */
65 /* ACTUAL LOG DATA FOLLOWS AT END OF STRUCT */
69 #define SizeOfXLogContRecord sizeof(XLogContRecord)
72 * Each page of XLOG file has a header like this:
74 #define XLOG_PAGE_MAGIC 0xD166 /* can be used as WAL version indicator */
76 typedef struct XLogPageHeaderData
78 uint16 xlp_magic; /* magic value for correctness checks */
79 uint16 xlp_info; /* flag bits, see below */
80 TimeLineID xlp_tli; /* TimeLineID of first record on page */
81 XLogRecPtr xlp_pageaddr; /* XLOG address of this page */
84 #define SizeOfXLogShortPHD MAXALIGN(sizeof(XLogPageHeaderData))
86 typedef XLogPageHeaderData *XLogPageHeader;
89 * When the XLP_LONG_HEADER flag is set, we store additional fields in the
90 * page header. (This is ordinarily done just in the first page of an
91 * XLOG file.) The additional fields serve to identify the file accurately.
93 typedef struct XLogLongPageHeaderData
95 XLogPageHeaderData std; /* standard header fields */
96 uint64 xlp_sysid; /* system identifier from pg_control */
97 uint32 xlp_seg_size; /* just as a cross-check */
98 uint32 xlp_xlog_blcksz; /* just as a cross-check */
99 } XLogLongPageHeaderData;
101 #define SizeOfXLogLongPHD MAXALIGN(sizeof(XLogLongPageHeaderData))
103 typedef XLogLongPageHeaderData *XLogLongPageHeader;
105 /* When record crosses page boundary, set this flag in new page's header */
106 #define XLP_FIRST_IS_CONTRECORD 0x0001
107 /* This flag indicates a "long" page header */
108 #define XLP_LONG_HEADER 0x0002
109 /* All defined flag bits in xlp_info (used for validity checking of header) */
110 #define XLP_ALL_FLAGS 0x0003
112 #define XLogPageHeaderSize(hdr) \
113 (((hdr)->xlp_info & XLP_LONG_HEADER) ? SizeOfXLogLongPHD : SizeOfXLogShortPHD)
116 * We break each logical log file (xlogid value) into segment files of the
117 * size indicated by XLOG_SEG_SIZE. One possible segment at the end of each
118 * log file is wasted, to ensure that we don't have problems representing
119 * last-byte-position-plus-1.
121 #define XLogSegSize ((uint32) XLOG_SEG_SIZE)
122 #define XLogSegsPerFile (((uint32) 0xffffffff) / XLogSegSize)
123 #define XLogFileSize (XLogSegsPerFile * XLogSegSize)
127 * Macros for manipulating XLOG pointers
130 /* Increment an xlogid/segment pair */
131 #define NextLogSeg(logId, logSeg) \
133 if ((logSeg) >= XLogSegsPerFile-1) \
142 /* Decrement an xlogid/segment pair (assume it's not 0,0) */
143 #define PrevLogSeg(logId, logSeg) \
150 (logSeg) = XLogSegsPerFile-1; \
154 /* Align a record pointer to next page */
155 #define NextLogPage(recptr) \
157 if (recptr.xrecoff % XLOG_BLCKSZ != 0) \
159 (XLOG_BLCKSZ - recptr.xrecoff % XLOG_BLCKSZ); \
160 if (recptr.xrecoff >= XLogFileSize) \
163 recptr.xrecoff = 0; \
168 * Compute ID and segment from an XLogRecPtr.
170 * For XLByteToSeg, do the computation at face value. For XLByteToPrevSeg,
171 * a boundary byte is taken to be in the previous segment. This is suitable
172 * for deciding which segment to write given a pointer to a record end,
173 * for example. (We can assume xrecoff is not zero, since no valid recptr
176 #define XLByteToSeg(xlrp, logId, logSeg) \
177 ( logId = (xlrp).xlogid, \
178 logSeg = (xlrp).xrecoff / XLogSegSize \
180 #define XLByteToPrevSeg(xlrp, logId, logSeg) \
181 ( logId = (xlrp).xlogid, \
182 logSeg = ((xlrp).xrecoff - 1) / XLogSegSize \
186 * Is an XLogRecPtr within a particular XLOG segment?
188 * For XLByteInSeg, do the computation at face value. For XLByteInPrevSeg,
189 * a boundary byte is taken to be in the previous segment.
191 #define XLByteInSeg(xlrp, logId, logSeg) \
192 ((xlrp).xlogid == (logId) && \
193 (xlrp).xrecoff / XLogSegSize == (logSeg))
195 #define XLByteInPrevSeg(xlrp, logId, logSeg) \
196 ((xlrp).xlogid == (logId) && \
197 ((xlrp).xrecoff - 1) / XLogSegSize == (logSeg))
199 /* Check if an xrecoff value is in a plausible range */
200 #define XRecOffIsValid(xrecoff) \
201 ((xrecoff) % XLOG_BLCKSZ >= SizeOfXLogShortPHD && \
202 (XLOG_BLCKSZ - (xrecoff) % XLOG_BLCKSZ) >= SizeOfXLogRecord)
205 * The XLog directory and control file (relative to $PGDATA)
207 #define XLOGDIR "pg_xlog"
208 #define XLOG_CONTROL_FILE "global/pg_control"
211 * These macros encapsulate knowledge about the exact layout of XLog file
212 * names, timeline history file names, and archive-status file names.
214 #define MAXFNAMELEN 64
216 #define XLogFileName(fname, tli, log, seg) \
217 snprintf(fname, MAXFNAMELEN, "%08X%08X%08X", tli, log, seg)
219 #define XLogFilePath(path, tli, log, seg) \
220 snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X", tli, log, seg)
222 #define TLHistoryFileName(fname, tli) \
223 snprintf(fname, MAXFNAMELEN, "%08X.history", tli)
225 #define TLHistoryFilePath(path, tli) \
226 snprintf(path, MAXPGPATH, XLOGDIR "/%08X.history", tli)
228 #define StatusFilePath(path, xlog, suffix) \
229 snprintf(path, MAXPGPATH, XLOGDIR "/archive_status/%s%s", xlog, suffix)
231 #define BackupHistoryFileName(fname, tli, log, seg, offset) \
232 snprintf(fname, MAXFNAMELEN, "%08X%08X%08X.%08X.backup", tli, log, seg, offset)
234 #define BackupHistoryFilePath(path, tli, log, seg, offset) \
235 snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X.%08X.backup", tli, log, seg, offset)
239 * Method table for resource managers.
241 * RmgrTable[] is indexed by RmgrId values (see rmgr.h).
243 typedef struct RmgrData
246 void (*rm_redo) (XLogRecPtr lsn, XLogRecord *rptr);
247 void (*rm_desc) (StringInfo buf, uint8 xl_info, char *rec);
248 void (*rm_startup) (void);
249 void (*rm_cleanup) (void);
250 bool (*rm_safe_restartpoint) (void);
253 extern const RmgrData RmgrTable[];
256 * Exported to support xlog switching from bgwriter
258 extern pg_time_t GetLastSegSwitchTime(void);
259 extern XLogRecPtr RequestXLogSwitch(void);
262 * These aren't in xlog.h because I'd rather not include fmgr.h there.
264 extern Datum pg_start_backup(PG_FUNCTION_ARGS);
265 extern Datum pg_stop_backup(PG_FUNCTION_ARGS);
266 extern Datum pg_switch_xlog(PG_FUNCTION_ARGS);
267 extern Datum pg_current_xlog_location(PG_FUNCTION_ARGS);
268 extern Datum pg_current_xlog_insert_location(PG_FUNCTION_ARGS);
269 extern Datum pg_last_xlog_receive_location(PG_FUNCTION_ARGS);
270 extern Datum pg_last_xlog_replay_location(PG_FUNCTION_ARGS);
271 extern Datum pg_xlogfile_name_offset(PG_FUNCTION_ARGS);
272 extern Datum pg_xlogfile_name(PG_FUNCTION_ARGS);
273 extern Datum pg_is_in_recovery(PG_FUNCTION_ARGS);
275 #endif /* XLOG_INTERNAL_H */