PostgreSQL Source Code  git master
pg_control.h
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * pg_control.h
4  * The system control file "pg_control" is not a heap relation.
5  * However, we define it here so that the format is documented.
6  *
7  *
8  * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
9  * Portions Copyright (c) 1994, Regents of the University of California
10  *
11  * src/include/catalog/pg_control.h
12  *
13  *-------------------------------------------------------------------------
14  */
15 #ifndef PG_CONTROL_H
16 #define PG_CONTROL_H
17 
18 #include "access/xlogdefs.h"
19 #include "pgtime.h" /* for pg_time_t */
20 #include "port/pg_crc32c.h"
21 
22 
23 /* Version identifier for this pg_control format */
24 #define PG_CONTROL_VERSION 1100
25 
26 /* Nonce key length, see below */
27 #define MOCK_AUTH_NONCE_LEN 32
28 
29 /*
30  * Body of CheckPoint XLOG records. This is declared here because we keep
31  * a copy of the latest one in pg_control for possible disaster recovery.
32  * Changing this struct requires a PG_CONTROL_VERSION bump.
33  */
34 typedef struct CheckPoint
35 {
36  XLogRecPtr redo; /* next RecPtr available when we began to
37  * create CheckPoint (i.e. REDO start point) */
38  TimeLineID ThisTimeLineID; /* current TLI */
39  TimeLineID PrevTimeLineID; /* previous TLI, if this record begins a new
40  * timeline (equals ThisTimeLineID otherwise) */
41  bool fullPageWrites; /* current full_page_writes */
42  uint32 nextXidEpoch; /* higher-order bits of nextXid */
43  TransactionId nextXid; /* next free XID */
44  Oid nextOid; /* next free OID */
45  MultiXactId nextMulti; /* next free MultiXactId */
46  MultiXactOffset nextMultiOffset; /* next free MultiXact offset */
47  TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */
48  Oid oldestXidDB; /* database with minimum datfrozenxid */
49  MultiXactId oldestMulti; /* cluster-wide minimum datminmxid */
50  Oid oldestMultiDB; /* database with minimum datminmxid */
51  pg_time_t time; /* time stamp of checkpoint */
52  TransactionId oldestCommitTsXid; /* oldest Xid with valid commit
53  * timestamp */
54  TransactionId newestCommitTsXid; /* newest Xid with valid commit
55  * timestamp */
56 
57  /*
58  * Oldest XID still running. This is only needed to initialize hot standby
59  * mode from an online checkpoint, so we only bother calculating this for
60  * online checkpoints and only when wal_level is replica. Otherwise it's
61  * set to InvalidTransactionId.
62  */
64 } CheckPoint;
65 
66 /* XLOG info values for XLOG rmgr */
67 #define XLOG_CHECKPOINT_SHUTDOWN 0x00
68 #define XLOG_CHECKPOINT_ONLINE 0x10
69 #define XLOG_NOOP 0x20
70 #define XLOG_NEXTOID 0x30
71 #define XLOG_SWITCH 0x40
72 #define XLOG_BACKUP_END 0x50
73 #define XLOG_PARAMETER_CHANGE 0x60
74 #define XLOG_RESTORE_POINT 0x70
75 #define XLOG_FPW_CHANGE 0x80
76 #define XLOG_END_OF_RECOVERY 0x90
77 #define XLOG_FPI_FOR_HINT 0xA0
78 #define XLOG_FPI 0xB0
79 
80 
81 /*
82  * System status indicator. Note this is stored in pg_control; if you change
83  * it, you must bump PG_CONTROL_VERSION
84  */
85 typedef enum DBState
86 {
94 } DBState;
95 
96 /*
97  * Contents of pg_control.
98  */
99 
100 typedef struct ControlFileData
101 {
102  /*
103  * Unique system identifier --- to ensure we match up xlog files with the
104  * installation that produced them.
105  */
107 
108  /*
109  * Version identifier information. Keep these fields at the same offset,
110  * especially pg_control_version; they won't be real useful if they move
111  * around. (For historical reasons they must be 8 bytes into the file
112  * rather than immediately at the front.)
113  *
114  * pg_control_version identifies the format of pg_control itself.
115  * catalog_version_no identifies the format of the system catalogs.
116  *
117  * There are additional version identifiers in individual files; for
118  * example, WAL logs contain per-page magic numbers that can serve as
119  * version cues for the WAL log.
120  */
121  uint32 pg_control_version; /* PG_CONTROL_VERSION */
122  uint32 catalog_version_no; /* see catversion.h */
123 
124  /*
125  * System status data
126  */
127  DBState state; /* see enum above */
128  pg_time_t time; /* time stamp of last pg_control update */
129  XLogRecPtr checkPoint; /* last check point record ptr */
130 
131  CheckPoint checkPointCopy; /* copy of last check point record */
132 
133  XLogRecPtr unloggedLSN; /* current fake LSN value, for unlogged rels */
134 
135  /*
136  * These two values determine the minimum point we must recover up to
137  * before starting up:
138  *
139  * minRecoveryPoint is updated to the latest replayed LSN whenever we
140  * flush a data change during archive recovery. That guards against
141  * starting archive recovery, aborting it, and restarting with an earlier
142  * stop location. If we've already flushed data changes from WAL record X
143  * to disk, we mustn't start up until we reach X again. Zero when not
144  * doing archive recovery.
145  *
146  * backupStartPoint is the redo pointer of the backup start checkpoint, if
147  * we are recovering from an online backup and haven't reached the end of
148  * backup yet. It is reset to zero when the end of backup is reached, and
149  * we mustn't start up before that. A boolean would suffice otherwise, but
150  * we use the redo pointer as a cross-check when we see an end-of-backup
151  * record, to make sure the end-of-backup record corresponds the base
152  * backup we're recovering from.
153  *
154  * backupEndPoint is the backup end location, if we are recovering from an
155  * online backup which was taken from the standby and haven't reached the
156  * end of backup yet. It is initialized to the minimum recovery point in
157  * pg_control which was backed up last. It is reset to zero when the end
158  * of backup is reached, and we mustn't start up before that.
159  *
160  * If backupEndRequired is true, we know for sure that we're restoring
161  * from a backup, and must see a backup-end record before we can safely
162  * start up. If it's false, but backupStartPoint is set, a backup_label
163  * file was found at startup but it may have been a leftover from a stray
164  * pg_start_backup() call, not accompanied by pg_stop_backup().
165  */
171 
172  /*
173  * Parameter settings that determine if the WAL can be used for archival
174  * or hot standby.
175  */
183 
184  /*
185  * This data is used to check for hardware-architecture compatibility of
186  * the database and the backend executable. We need not check endianness
187  * explicitly, since the pg_control version will surely look wrong to a
188  * machine of different endianness, but we do need to worry about MAXALIGN
189  * and floating-point format. (Note: storage layout nominally also
190  * depends on SHORTALIGN and INTALIGN, but in practice these are the same
191  * on all architectures of interest.)
192  *
193  * Testing just one double value is not a very bulletproof test for
194  * floating-point compatibility, but it will catch most cases.
195  */
196  uint32 maxAlign; /* alignment requirement for tuples */
197  double floatFormat; /* constant 1234567.0 */
198 #define FLOATFORMAT_VALUE 1234567.0
199 
200  /*
201  * This data is used to make sure that configuration of this database is
202  * compatible with the backend executable.
203  */
204  uint32 blcksz; /* data block size for this DB */
205  uint32 relseg_size; /* blocks per segment of large relation */
206 
207  uint32 xlog_blcksz; /* block size within WAL files */
208  uint32 xlog_seg_size; /* size of each WAL segment */
209 
210  uint32 nameDataLen; /* catalog name field width */
211  uint32 indexMaxKeys; /* max number of columns in an index */
212 
213  uint32 toast_max_chunk_size; /* chunk size in TOAST tables */
214  uint32 loblksize; /* chunk size in pg_largeobject */
215 
216  /* flags indicating pass-by-value status of various types */
217  bool float4ByVal; /* float4 pass-by-value? */
218  bool float8ByVal; /* float8, int8, etc pass-by-value? */
219 
220  /* Are data pages protected by checksums? Zero if no checksum version */
222 
223  /*
224  * Random nonce, used in authentication requests that need to proceed
225  * based on values that are cluster-unique, like a SASL exchange that
226  * failed at an early stage.
227  */
228  char mock_authentication_nonce[MOCK_AUTH_NONCE_LEN];
229 
230  /* CRC of all above ... MUST BE LAST! */
233 
234 /*
235  * Maximum safe value of sizeof(ControlFileData). For reliability's sake,
236  * it's critical that pg_control updates be atomic writes. That generally
237  * means the active data can't be more than one disk sector, which is 512
238  * bytes on common hardware. Be very careful about raising this limit.
239  */
240 #define PG_CONTROL_MAX_SAFE_SIZE 512
241 
242 /*
243  * Physical size of the pg_control file. Note that this is considerably
244  * bigger than the actually used size (ie, sizeof(ControlFileData)).
245  * The idea is to keep the physical size constant independent of format
246  * changes, so that ReadControlFile will deliver a suitable wrong-version
247  * message instead of a read error if it's looking at an incompatible file.
248  */
249 #define PG_CONTROL_FILE_SIZE 8192
250 
251 #endif /* PG_CONTROL_H */
int max_locks_per_xact
Definition: pg_control.h:181
int max_prepared_xacts
Definition: pg_control.h:180
uint32 TimeLineID
Definition: xlogdefs.h:45
int64 pg_time_t
Definition: pgtime.h:23
uint32 MultiXactOffset
Definition: c.h:486
pg_time_t time
Definition: pg_control.h:128
uint32 TransactionId
Definition: c.h:474
TimeLineID minRecoveryPointTLI
Definition: pg_control.h:167
int max_worker_processes
Definition: pg_control.h:179
uint32 pg_crc32c
Definition: pg_crc32c.h:38
TransactionId oldestActiveXid
Definition: pg_control.h:63
uint32 nameDataLen
Definition: pg_control.h:210
MultiXactId oldestMulti
Definition: pg_control.h:49
TimeLineID PrevTimeLineID
Definition: pg_control.h:39
uint32 pg_control_version
Definition: pg_control.h:121
CheckPoint checkPointCopy
Definition: pg_control.h:131
uint32 xlog_blcksz
Definition: pg_control.h:207
TransactionId oldestXid
Definition: pg_control.h:47
unsigned int Oid
Definition: postgres_ext.h:31
TransactionId nextXid
Definition: pg_control.h:43
pg_time_t time
Definition: pg_control.h:51
#define MOCK_AUTH_NONCE_LEN
Definition: pg_control.h:27
bool backupEndRequired
Definition: pg_control.h:170
MultiXactOffset nextMultiOffset
Definition: pg_control.h:46
TransactionId oldestCommitTsXid
Definition: pg_control.h:52
uint32 xlog_seg_size
Definition: pg_control.h:208
uint64 system_identifier
Definition: pg_control.h:106
uint32 nextXidEpoch
Definition: pg_control.h:42
uint32 data_checksum_version
Definition: pg_control.h:221
struct ControlFileData ControlFileData
XLogRecPtr unloggedLSN
Definition: pg_control.h:133
unsigned int uint32
Definition: c.h:325
pg_crc32c crc
Definition: pg_control.h:231
uint32 loblksize
Definition: pg_control.h:214
uint32 indexMaxKeys
Definition: pg_control.h:211
DBState
Definition: pg_control.h:85
TransactionId newestCommitTsXid
Definition: pg_control.h:54
Oid oldestMultiDB
Definition: pg_control.h:50
uint32 toast_max_chunk_size
Definition: pg_control.h:213
Oid nextOid
Definition: pg_control.h:44
XLogRecPtr backupEndPoint
Definition: pg_control.h:169
bool fullPageWrites
Definition: pg_control.h:41
TransactionId MultiXactId
Definition: c.h:484
bool track_commit_timestamp
Definition: pg_control.h:182
uint64 XLogRecPtr
Definition: xlogdefs.h:21
Oid oldestXidDB
Definition: pg_control.h:48
double floatFormat
Definition: pg_control.h:197
MultiXactId nextMulti
Definition: pg_control.h:45
uint32 catalog_version_no
Definition: pg_control.h:122
struct CheckPoint CheckPoint
TimeLineID ThisTimeLineID
Definition: pg_control.h:38
XLogRecPtr backupStartPoint
Definition: pg_control.h:168
uint32 relseg_size
Definition: pg_control.h:205
XLogRecPtr checkPoint
Definition: pg_control.h:129
XLogRecPtr redo
Definition: pg_control.h:36
XLogRecPtr minRecoveryPoint
Definition: pg_control.h:166