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xlog_internal.h
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1 /*
2  * xlog_internal.h
3  *
4  * PostgreSQL write-ahead log internal declarations
5  *
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 xlogrecord.h.
10  *
11  * Note: This file must be includable in both frontend and backend contexts,
12  * to allow stand-alone tools like pg_receivewal to deal with WAL files.
13  *
14  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
15  * Portions Copyright (c) 1994, Regents of the University of California
16  *
17  * src/include/access/xlog_internal.h
18  */
19 #ifndef XLOG_INTERNAL_H
20 #define XLOG_INTERNAL_H
21 
22 #include "access/xlogdefs.h"
23 #include "access/xlogreader.h"
24 #include "datatype/timestamp.h"
25 #include "lib/stringinfo.h"
26 #include "pgtime.h"
27 #include "storage/block.h"
28 #include "storage/relfilenode.h"
29 
30 
31 /*
32  * Each page of XLOG file has a header like this:
33  */
34 #define XLOG_PAGE_MAGIC 0xD10E /* can be used as WAL version indicator */
35 
36 typedef struct XLogPageHeaderData
37 {
38  uint16 xlp_magic; /* magic value for correctness checks */
39  uint16 xlp_info; /* flag bits, see below */
40  TimeLineID xlp_tli; /* TimeLineID of first record on page */
41  XLogRecPtr xlp_pageaddr; /* XLOG address of this page */
42 
43  /*
44  * When there is not enough space on current page for whole record, we
45  * continue on the next page. xlp_rem_len is the number of bytes
46  * remaining from a previous page; it tracks xl_tot_len in the initial
47  * header. Note that the continuation data isn't necessarily aligned.
48  */
49  uint32 xlp_rem_len; /* total len of remaining data for record */
51 
52 #define SizeOfXLogShortPHD MAXALIGN(sizeof(XLogPageHeaderData))
53 
55 
56 /*
57  * When the XLP_LONG_HEADER flag is set, we store additional fields in the
58  * page header. (This is ordinarily done just in the first page of an
59  * XLOG file.) The additional fields serve to identify the file accurately.
60  */
61 typedef struct XLogLongPageHeaderData
62 {
63  XLogPageHeaderData std; /* standard header fields */
64  uint64 xlp_sysid; /* system identifier from pg_control */
65  uint32 xlp_seg_size; /* just as a cross-check */
66  uint32 xlp_xlog_blcksz; /* just as a cross-check */
68 
69 #define SizeOfXLogLongPHD MAXALIGN(sizeof(XLogLongPageHeaderData))
70 
72 
73 /* When record crosses page boundary, set this flag in new page's header */
74 #define XLP_FIRST_IS_CONTRECORD 0x0001
75 /* This flag indicates a "long" page header */
76 #define XLP_LONG_HEADER 0x0002
77 /* This flag indicates backup blocks starting in this page are optional */
78 #define XLP_BKP_REMOVABLE 0x0004
79 /* Replaces a missing contrecord; see CreateOverwriteContrecordRecord */
80 #define XLP_FIRST_IS_OVERWRITE_CONTRECORD 0x0008
81 /* All defined flag bits in xlp_info (used for validity checking of header) */
82 #define XLP_ALL_FLAGS 0x000F
83 
84 #define XLogPageHeaderSize(hdr) \
85  (((hdr)->xlp_info & XLP_LONG_HEADER) ? SizeOfXLogLongPHD : SizeOfXLogShortPHD)
86 
87 /* wal_segment_size can range from 1MB to 1GB */
88 #define WalSegMinSize 1024 * 1024
89 #define WalSegMaxSize 1024 * 1024 * 1024
90 /* default number of min and max wal segments */
91 #define DEFAULT_MIN_WAL_SEGS 5
92 #define DEFAULT_MAX_WAL_SEGS 64
93 
94 /* check that the given size is a valid wal_segment_size */
95 #define IsPowerOf2(x) (x > 0 && ((x) & ((x)-1)) == 0)
96 #define IsValidWalSegSize(size) \
97  (IsPowerOf2(size) && \
98  ((size) >= WalSegMinSize && (size) <= WalSegMaxSize))
99 
100 #define XLogSegmentsPerXLogId(wal_segsz_bytes) \
101  (UINT64CONST(0x100000000) / (wal_segsz_bytes))
102 
103 #define XLogSegNoOffsetToRecPtr(segno, offset, wal_segsz_bytes, dest) \
104  (dest) = (segno) * (wal_segsz_bytes) + (offset)
105 
106 #define XLogSegmentOffset(xlogptr, wal_segsz_bytes) \
107  ((xlogptr) & ((wal_segsz_bytes) - 1))
108 
109 /*
110  * Compute a segment number from an XLogRecPtr.
111  *
112  * For XLByteToSeg, do the computation at face value. For XLByteToPrevSeg,
113  * a boundary byte is taken to be in the previous segment. This is suitable
114  * for deciding which segment to write given a pointer to a record end,
115  * for example.
116  */
117 #define XLByteToSeg(xlrp, logSegNo, wal_segsz_bytes) \
118  logSegNo = (xlrp) / (wal_segsz_bytes)
119 
120 #define XLByteToPrevSeg(xlrp, logSegNo, wal_segsz_bytes) \
121  logSegNo = ((xlrp) - 1) / (wal_segsz_bytes)
122 
123 /*
124  * Convert values of GUCs measured in megabytes to equiv. segment count.
125  * Rounds down.
126  */
127 #define XLogMBVarToSegs(mbvar, wal_segsz_bytes) \
128  ((mbvar) / ((wal_segsz_bytes) / (1024 * 1024)))
129 
130 /*
131  * Is an XLogRecPtr within a particular XLOG segment?
132  *
133  * For XLByteInSeg, do the computation at face value. For XLByteInPrevSeg,
134  * a boundary byte is taken to be in the previous segment.
135  */
136 #define XLByteInSeg(xlrp, logSegNo, wal_segsz_bytes) \
137  (((xlrp) / (wal_segsz_bytes)) == (logSegNo))
138 
139 #define XLByteInPrevSeg(xlrp, logSegNo, wal_segsz_bytes) \
140  ((((xlrp) - 1) / (wal_segsz_bytes)) == (logSegNo))
141 
142 /* Check if an XLogRecPtr value is in a plausible range */
143 #define XRecOffIsValid(xlrp) \
144  ((xlrp) % XLOG_BLCKSZ >= SizeOfXLogShortPHD)
145 
146 /*
147  * The XLog directory and control file (relative to $PGDATA)
148  */
149 #define XLOGDIR "pg_wal"
150 #define XLOG_CONTROL_FILE "global/pg_control"
151 
152 /*
153  * These macros encapsulate knowledge about the exact layout of XLog file
154  * names, timeline history file names, and archive-status file names.
155  */
156 #define MAXFNAMELEN 64
157 
158 /* Length of XLog file name */
159 #define XLOG_FNAME_LEN 24
160 
161 /*
162  * Generate a WAL segment file name. Do not use this macro in a helper
163  * function allocating the result generated.
164  */
165 #define XLogFileName(fname, tli, logSegNo, wal_segsz_bytes) \
166  snprintf(fname, MAXFNAMELEN, "%08X%08X%08X", tli, \
167  (uint32) ((logSegNo) / XLogSegmentsPerXLogId(wal_segsz_bytes)), \
168  (uint32) ((logSegNo) % XLogSegmentsPerXLogId(wal_segsz_bytes)))
169 
170 #define XLogFileNameById(fname, tli, log, seg) \
171  snprintf(fname, MAXFNAMELEN, "%08X%08X%08X", tli, log, seg)
172 
173 #define IsXLogFileName(fname) \
174  (strlen(fname) == XLOG_FNAME_LEN && \
175  strspn(fname, "0123456789ABCDEF") == XLOG_FNAME_LEN)
176 
177 /*
178  * XLOG segment with .partial suffix. Used by pg_receivewal and at end of
179  * archive recovery, when we want to archive a WAL segment but it might not
180  * be complete yet.
181  */
182 #define IsPartialXLogFileName(fname) \
183  (strlen(fname) == XLOG_FNAME_LEN + strlen(".partial") && \
184  strspn(fname, "0123456789ABCDEF") == XLOG_FNAME_LEN && \
185  strcmp((fname) + XLOG_FNAME_LEN, ".partial") == 0)
186 
187 #define XLogFromFileName(fname, tli, logSegNo, wal_segsz_bytes) \
188  do { \
189  uint32 log; \
190  uint32 seg; \
191  sscanf(fname, "%08X%08X%08X", tli, &log, &seg); \
192  *logSegNo = (uint64) log * XLogSegmentsPerXLogId(wal_segsz_bytes) + seg; \
193  } while (0)
194 
195 #define XLogFilePath(path, tli, logSegNo, wal_segsz_bytes) \
196  snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X", tli, \
197  (uint32) ((logSegNo) / XLogSegmentsPerXLogId(wal_segsz_bytes)), \
198  (uint32) ((logSegNo) % XLogSegmentsPerXLogId(wal_segsz_bytes)))
199 
200 #define TLHistoryFileName(fname, tli) \
201  snprintf(fname, MAXFNAMELEN, "%08X.history", tli)
202 
203 #define IsTLHistoryFileName(fname) \
204  (strlen(fname) == 8 + strlen(".history") && \
205  strspn(fname, "0123456789ABCDEF") == 8 && \
206  strcmp((fname) + 8, ".history") == 0)
207 
208 #define TLHistoryFilePath(path, tli) \
209  snprintf(path, MAXPGPATH, XLOGDIR "/%08X.history", tli)
210 
211 #define StatusFilePath(path, xlog, suffix) \
212  snprintf(path, MAXPGPATH, XLOGDIR "/archive_status/%s%s", xlog, suffix)
213 
214 #define BackupHistoryFileName(fname, tli, logSegNo, startpoint, wal_segsz_bytes) \
215  snprintf(fname, MAXFNAMELEN, "%08X%08X%08X.%08X.backup", tli, \
216  (uint32) ((logSegNo) / XLogSegmentsPerXLogId(wal_segsz_bytes)), \
217  (uint32) ((logSegNo) % XLogSegmentsPerXLogId(wal_segsz_bytes)), \
218  (uint32) (XLogSegmentOffset(startpoint, wal_segsz_bytes)))
219 
220 #define IsBackupHistoryFileName(fname) \
221  (strlen(fname) > XLOG_FNAME_LEN && \
222  strspn(fname, "0123456789ABCDEF") == XLOG_FNAME_LEN && \
223  strcmp((fname) + strlen(fname) - strlen(".backup"), ".backup") == 0)
224 
225 #define BackupHistoryFilePath(path, tli, logSegNo, startpoint, wal_segsz_bytes) \
226  snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X.%08X.backup", tli, \
227  (uint32) ((logSegNo) / XLogSegmentsPerXLogId(wal_segsz_bytes)), \
228  (uint32) ((logSegNo) % XLogSegmentsPerXLogId(wal_segsz_bytes)), \
229  (uint32) (XLogSegmentOffset((startpoint), wal_segsz_bytes)))
230 
231 /*
232  * Information logged when we detect a change in one of the parameters
233  * important for Hot Standby.
234  */
235 typedef struct xl_parameter_change
236 {
246 
247 /* logs restore point */
248 typedef struct xl_restore_point
249 {
253 
254 /* Overwrite of prior contrecord */
256 {
260 
261 /* End of recovery mark, when we don't do an END_OF_RECOVERY checkpoint */
262 typedef struct xl_end_of_recovery
263 {
265  TimeLineID ThisTimeLineID; /* new TLI */
266  TimeLineID PrevTimeLineID; /* previous TLI we forked off from */
268 
269 /*
270  * The functions in xloginsert.c construct a chain of XLogRecData structs
271  * to represent the final WAL record.
272  */
273 typedef struct XLogRecData
274 {
275  struct XLogRecData *next; /* next struct in chain, or NULL */
276  char *data; /* start of rmgr data to include */
277  uint32 len; /* length of rmgr data to include */
279 
280 /*
281  * Recovery target action.
282  */
283 typedef enum
284 {
289 
290 /*
291  * Method table for resource managers.
292  *
293  * This struct must be kept in sync with the PG_RMGR definition in
294  * rmgr.c.
295  *
296  * rm_identify must return a name for the record based on xl_info (without
297  * reference to the rmid). For example, XLOG_BTREE_VACUUM would be named
298  * "VACUUM". rm_desc can then be called to obtain additional detail for the
299  * record, if available (e.g. the last block).
300  *
301  * rm_mask takes as input a page modified by the resource manager and masks
302  * out bits that shouldn't be flagged by wal_consistency_checking.
303  *
304  * RmgrTable[] is indexed by RmgrId values (see rmgrlist.h).
305  */
306 typedef struct RmgrData
307 {
308  const char *rm_name;
309  void (*rm_redo) (XLogReaderState *record);
310  void (*rm_desc) (StringInfo buf, XLogReaderState *record);
311  const char *(*rm_identify) (uint8 info);
312  void (*rm_startup) (void);
313  void (*rm_cleanup) (void);
314  void (*rm_mask) (char *pagedata, BlockNumber blkno);
316 
317 extern const RmgrData RmgrTable[];
318 
319 /*
320  * Exported to support xlog switching from checkpointer
321  */
322 extern pg_time_t GetLastSegSwitchData(XLogRecPtr *lastSwitchLSN);
323 extern XLogRecPtr RequestXLogSwitch(bool mark_unimportant);
324 
325 extern void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli);
326 
327 /*
328  * Exported for the functions in timeline.c and xlogarchive.c. Only valid
329  * in the startup process.
330  */
331 extern bool ArchiveRecoveryRequested;
332 extern bool InArchiveRecovery;
333 extern bool StandbyMode;
334 extern char *recoveryRestoreCommand;
335 
336 #endif /* XLOG_INTERNAL_H */
uint32 BlockNumber
Definition: block.h:31
unsigned short uint16
Definition: c.h:440
unsigned int uint32
Definition: c.h:441
unsigned char uint8
Definition: c.h:439
int64 TimestampTz
Definition: timestamp.h:39
static char * buf
Definition: pg_test_fsync.c:69
int64 pg_time_t
Definition: pgtime.h:23
void(* rm_mask)(char *pagedata, BlockNumber blkno)
void(* rm_redo)(XLogReaderState *record)
void(* rm_cleanup)(void)
const char * rm_name
void(* rm_startup)(void)
void(* rm_desc)(StringInfo buf, XLogReaderState *record)
XLogPageHeaderData std
Definition: xlog_internal.h:63
TimeLineID xlp_tli
Definition: xlog_internal.h:40
XLogRecPtr xlp_pageaddr
Definition: xlog_internal.h:41
struct XLogRecData * next
TimeLineID PrevTimeLineID
TimestampTz end_time
TimeLineID ThisTimeLineID
char rp_name[MAXFNAMELEN]
TimestampTz rp_time
const RmgrData RmgrTable[]
Definition: rmgr.c:36
struct xl_overwrite_contrecord xl_overwrite_contrecord
struct XLogLongPageHeaderData XLogLongPageHeaderData
XLogRecPtr RequestXLogSwitch(bool mark_unimportant)
Definition: xlog.c:10122
struct xl_restore_point xl_restore_point
XLogLongPageHeaderData * XLogLongPageHeader
Definition: xlog_internal.h:71
struct XLogRecData XLogRecData
RecoveryTargetAction
@ RECOVERY_TARGET_ACTION_PAUSE
@ RECOVERY_TARGET_ACTION_PROMOTE
@ RECOVERY_TARGET_ACTION_SHUTDOWN
bool ArchiveRecoveryRequested
Definition: xlog.c:257
bool InArchiveRecovery
Definition: xlog.c:258
char * recoveryRestoreCommand
Definition: xlog.c:268
#define MAXFNAMELEN
pg_time_t GetLastSegSwitchData(XLogRecPtr *lastSwitchLSN)
Definition: xlog.c:8815
XLogPageHeaderData * XLogPageHeader
Definition: xlog_internal.h:54
bool StandbyMode
Definition: xlog.c:289
struct xl_parameter_change xl_parameter_change
void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli)
Definition: xlog.c:12053
struct XLogPageHeaderData XLogPageHeaderData
struct xl_end_of_recovery xl_end_of_recovery
struct RmgrData RmgrData
uint64 XLogRecPtr
Definition: xlogdefs.h:21
uint32 TimeLineID
Definition: xlogdefs.h:59