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nbtxlog.h
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1 /*-------------------------------------------------------------------------
2  *
3  * nbtxlog.h
4  * header file for postgres btree xlog routines
5  *
6  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  * src/include/access/nbtxlog.h
10  *
11  *-------------------------------------------------------------------------
12  */
13 #ifndef NBTXLOG_H
14 #define NBTXLOG_H
15 
16 #include "access/transam.h"
17 #include "access/xlogreader.h"
18 #include "lib/stringinfo.h"
19 #include "storage/off.h"
20 
21 /*
22  * XLOG records for btree operations
23  *
24  * XLOG allows to store some information in high 4 bits of log
25  * record xl_info field
26  */
27 #define XLOG_BTREE_INSERT_LEAF 0x00 /* add index tuple without split */
28 #define XLOG_BTREE_INSERT_UPPER 0x10 /* same, on a non-leaf page */
29 #define XLOG_BTREE_INSERT_META 0x20 /* same, plus update metapage */
30 #define XLOG_BTREE_SPLIT_L 0x30 /* add index tuple with split */
31 #define XLOG_BTREE_SPLIT_R 0x40 /* as above, new item on right */
32 #define XLOG_BTREE_INSERT_POST 0x50 /* add index tuple with posting split */
33 #define XLOG_BTREE_DEDUP 0x60 /* deduplicate tuples for a page */
34 #define XLOG_BTREE_DELETE 0x70 /* delete leaf index tuples for a page */
35 #define XLOG_BTREE_UNLINK_PAGE 0x80 /* delete a half-dead page */
36 #define XLOG_BTREE_UNLINK_PAGE_META 0x90 /* same, and update metapage */
37 #define XLOG_BTREE_NEWROOT 0xA0 /* new root page */
38 #define XLOG_BTREE_MARK_PAGE_HALFDEAD 0xB0 /* mark a leaf as half-dead */
39 #define XLOG_BTREE_VACUUM 0xC0 /* delete entries on a page during
40  * vacuum */
41 #define XLOG_BTREE_REUSE_PAGE 0xD0 /* old page is about to be reused from
42  * FSM */
43 #define XLOG_BTREE_META_CLEANUP 0xE0 /* update cleanup-related data in the
44  * metapage */
45 
46 /*
47  * All that we need to regenerate the meta-data page
48  */
49 typedef struct xl_btree_metadata
50 {
59 
60 /*
61  * This is what we need to know about simple (without split) insert.
62  *
63  * This data record is used for INSERT_LEAF, INSERT_UPPER, INSERT_META, and
64  * INSERT_POST. Note that INSERT_META and INSERT_UPPER implies it's not a
65  * leaf page, while INSERT_POST and INSERT_LEAF imply that it must be a leaf
66  * page.
67  *
68  * Backup Blk 0: original page
69  * Backup Blk 1: child's left sibling, if INSERT_UPPER or INSERT_META
70  * Backup Blk 2: xl_btree_metadata, if INSERT_META
71  *
72  * Note: The new tuple is actually the "original" new item in the posting
73  * list split insert case (i.e. the INSERT_POST case). A split offset for
74  * the posting list is logged before the original new item. Recovery needs
75  * both, since it must do an in-place update of the existing posting list
76  * that was split as an extra step. Also, recovery generates a "final"
77  * newitem. See _bt_swap_posting() for details on posting list splits.
78  */
79 typedef struct xl_btree_insert
80 {
82 
83  /* POSTING SPLIT OFFSET FOLLOWS (INSERT_POST case) */
84  /* NEW TUPLE ALWAYS FOLLOWS AT THE END */
86 
87 #define SizeOfBtreeInsert (offsetof(xl_btree_insert, offnum) + sizeof(OffsetNumber))
88 
89 /*
90  * On insert with split, we save all the items going into the right sibling
91  * so that we can restore it completely from the log record. This way takes
92  * less xlog space than the normal approach, because if we did it standardly,
93  * XLogInsert would almost always think the right page is new and store its
94  * whole page image. The left page, however, is handled in the normal
95  * incremental-update fashion.
96  *
97  * Note: XLOG_BTREE_SPLIT_L and XLOG_BTREE_SPLIT_R share this data record.
98  * There are two variants to indicate whether the inserted tuple went into the
99  * left or right split page (and thus, whether the new item is stored or not).
100  * We always log the left page high key because suffix truncation can generate
101  * a new leaf high key using user-defined code. This is also necessary on
102  * internal pages, since the firstright item that the left page's high key was
103  * based on will have been truncated to zero attributes in the right page (the
104  * separator key is unavailable from the right page).
105  *
106  * Backup Blk 0: original page / new left page
107  *
108  * The left page's data portion contains the new item, if it's the _L variant.
109  * _R variant split records generally do not have a newitem (_R variant leaf
110  * page split records that must deal with a posting list split will include an
111  * explicit newitem, though it is never used on the right page -- it is
112  * actually an orignewitem needed to update existing posting list). The new
113  * high key of the left/original page appears last of all (and must always be
114  * present).
115  *
116  * Page split records that need the REDO routine to deal with a posting list
117  * split directly will have an explicit newitem, which is actually an
118  * orignewitem (the newitem as it was before the posting list split, not
119  * after). A posting list split always has a newitem that comes immediately
120  * after the posting list being split (which would have overlapped with
121  * orignewitem prior to split). Usually REDO must deal with posting list
122  * splits with an _L variant page split record, and usually both the new
123  * posting list and the final newitem go on the left page (the existing
124  * posting list will be inserted instead of the old, and the final newitem
125  * will be inserted next to that). However, _R variant split records will
126  * include an orignewitem when the split point for the page happens to have a
127  * lastleft tuple that is also the posting list being split (leaving newitem
128  * as the page split's firstright tuple). The existence of this corner case
129  * does not change the basic fact about newitem/orignewitem for the REDO
130  * routine: it is always state used for the left page alone. (This is why the
131  * record's postingoff field isn't a reliable indicator of whether or not a
132  * posting list split occurred during the page split; a non-zero value merely
133  * indicates that the REDO routine must reconstruct a new posting list tuple
134  * that is needed for the left page.)
135  *
136  * This posting list split handling is equivalent to the xl_btree_insert REDO
137  * routine's INSERT_POST handling. While the details are more complicated
138  * here, the concept and goals are exactly the same. See _bt_swap_posting()
139  * for details on posting list splits.
140  *
141  * Backup Blk 1: new right page
142  *
143  * The right page's data portion contains the right page's tuples in the form
144  * used by _bt_restore_page. This includes the new item, if it's the _R
145  * variant. The right page's tuples also include the right page's high key
146  * with either variant (moved from the left/original page during the split),
147  * unless the split happened to be of the rightmost page on its level, where
148  * there is no high key for new right page.
149  *
150  * Backup Blk 2: next block (orig page's rightlink), if any
151  * Backup Blk 3: child's left sibling, if non-leaf split
152  */
153 typedef struct xl_btree_split
154 {
155  uint32 level; /* tree level of page being split */
156  OffsetNumber firstrightoff; /* first origpage item on rightpage */
157  OffsetNumber newitemoff; /* new item's offset */
158  uint16 postingoff; /* offset inside orig posting tuple */
160 
161 #define SizeOfBtreeSplit (offsetof(xl_btree_split, postingoff) + sizeof(uint16))
162 
163 /*
164  * When page is deduplicated, consecutive groups of tuples with equal keys are
165  * merged together into posting list tuples.
166  *
167  * The WAL record represents a deduplication pass for a leaf page. An array
168  * of BTDedupInterval structs follows.
169  */
170 typedef struct xl_btree_dedup
171 {
173 
174  /* DEDUPLICATION INTERVALS FOLLOW */
176 
177 #define SizeOfBtreeDedup (offsetof(xl_btree_dedup, nintervals) + sizeof(uint16))
178 
179 /*
180  * This is what we need to know about page reuse within btree. This record
181  * only exists to generate a conflict point for Hot Standby.
182  *
183  * Note that we must include a RelFileNode in the record because we don't
184  * actually register the buffer with the record.
185  */
186 typedef struct xl_btree_reuse_page
187 {
192 
193 #define SizeOfBtreeReusePage (sizeof(xl_btree_reuse_page))
194 
195 /*
196  * xl_btree_vacuum and xl_btree_delete records describe deletion of index
197  * tuples on a leaf page. The former variant is used by VACUUM, while the
198  * latter variant is used by the ad-hoc deletions that sometimes take place
199  * when btinsert() is called.
200  *
201  * The records are very similar. The only difference is that xl_btree_delete
202  * has to include a latestRemovedXid field to generate recovery conflicts.
203  * (VACUUM operations can just rely on earlier conflicts generated during
204  * pruning of the table whose TIDs the to-be-deleted index tuples point to.
205  * There are also small differences between each REDO routine that we don't go
206  * into here.)
207  *
208  * xl_btree_vacuum and xl_btree_delete both represent deletion of any number
209  * of index tuples on a single leaf page using page offset numbers. Both also
210  * support "updates" of index tuples, which is how deletes of a subset of TIDs
211  * contained in an existing posting list tuple are implemented.
212  *
213  * Updated posting list tuples are represented using xl_btree_update metadata.
214  * The REDO routines each use the xl_btree_update entries (plus each
215  * corresponding original index tuple from the target leaf page) to generate
216  * the final updated tuple.
217  *
218  * Updates are only used when there will be some remaining TIDs left by the
219  * REDO routine. Otherwise the posting list tuple just gets deleted outright.
220  */
221 typedef struct xl_btree_vacuum
222 {
225 
226  /* DELETED TARGET OFFSET NUMBERS FOLLOW */
227  /* UPDATED TARGET OFFSET NUMBERS FOLLOW */
228  /* UPDATED TUPLES METADATA (xl_btree_update) ARRAY FOLLOWS */
230 
231 #define SizeOfBtreeVacuum (offsetof(xl_btree_vacuum, nupdated) + sizeof(uint16))
232 
233 typedef struct xl_btree_delete
234 {
238 
239  /* DELETED TARGET OFFSET NUMBERS FOLLOW */
240  /* UPDATED TARGET OFFSET NUMBERS FOLLOW */
241  /* UPDATED TUPLES METADATA (xl_btree_update) ARRAY FOLLOWS */
243 
244 #define SizeOfBtreeDelete (offsetof(xl_btree_delete, nupdated) + sizeof(uint16))
245 
246 /*
247  * The offsets that appear in xl_btree_update metadata are offsets into the
248  * original posting list from tuple, not page offset numbers. These are
249  * 0-based. The page offset number for the original posting list tuple comes
250  * from the main xl_btree_vacuum/xl_btree_delete record.
251  */
252 typedef struct xl_btree_update
253 {
255 
256  /* POSTING LIST uint16 OFFSETS TO A DELETED TID FOLLOW */
258 
259 #define SizeOfBtreeUpdate (offsetof(xl_btree_update, ndeletedtids) + sizeof(uint16))
260 
261 /*
262  * This is what we need to know about marking an empty subtree for deletion.
263  * The target identifies the tuple removed from the parent page (note that we
264  * remove this tuple's downlink and the *following* tuple's key). Note that
265  * the leaf page is empty, so we don't need to store its content --- it is
266  * just reinitialized during recovery using the rest of the fields.
267  *
268  * Backup Blk 0: leaf block
269  * Backup Blk 1: top parent
270  */
272 {
273  OffsetNumber poffset; /* deleted tuple id in parent page */
274 
275  /* information needed to recreate the leaf page: */
276  BlockNumber leafblk; /* leaf block ultimately being deleted */
277  BlockNumber leftblk; /* leaf block's left sibling, if any */
278  BlockNumber rightblk; /* leaf block's right sibling */
279  BlockNumber topparent; /* topmost internal page in the subtree */
281 
282 #define SizeOfBtreeMarkPageHalfDead (offsetof(xl_btree_mark_page_halfdead, topparent) + sizeof(BlockNumber))
283 
284 /*
285  * This is what we need to know about deletion of a btree page. Note that we
286  * only leave behind a small amount of bookkeeping information in deleted
287  * pages (deleted pages must be kept around as tombstones for a while). It is
288  * convenient for the REDO routine to regenerate its target page from scratch.
289  * This is why WAL record describes certain details that are actually directly
290  * available from the target page.
291  *
292  * Backup Blk 0: target block being deleted
293  * Backup Blk 1: target block's left sibling, if any
294  * Backup Blk 2: target block's right sibling
295  * Backup Blk 3: leaf block (if different from target)
296  * Backup Blk 4: metapage (if rightsib becomes new fast root)
297  */
298 typedef struct xl_btree_unlink_page
299 {
300  BlockNumber leftsib; /* target block's left sibling, if any */
301  BlockNumber rightsib; /* target block's right sibling */
302  uint32 level; /* target block's level */
303  FullTransactionId safexid; /* target block's BTPageSetDeleted() XID */
304 
305  /*
306  * Information needed to recreate a half-dead leaf page with correct
307  * topparent link. The fields are only used when deletion operation's
308  * target page is an internal page. REDO routine creates half-dead page
309  * from scratch to keep things simple (this is the same convenient
310  * approach used for the target page itself).
311  */
314  BlockNumber leaftopparent; /* next child down in the subtree */
315 
316  /* xl_btree_metadata FOLLOWS IF XLOG_BTREE_UNLINK_PAGE_META */
318 
319 #define SizeOfBtreeUnlinkPage (offsetof(xl_btree_unlink_page, leaftopparent) + sizeof(BlockNumber))
320 
321 /*
322  * New root log record. There are zero tuples if this is to establish an
323  * empty root, or two if it is the result of splitting an old root.
324  *
325  * Note that although this implies rewriting the metadata page, we don't need
326  * an xl_btree_metadata record --- the rootblk and level are sufficient.
327  *
328  * Backup Blk 0: new root page (2 tuples as payload, if splitting old root)
329  * Backup Blk 1: left child (if splitting an old root)
330  * Backup Blk 2: metapage
331  */
332 typedef struct xl_btree_newroot
333 {
334  BlockNumber rootblk; /* location of new root (redundant with blk 0) */
335  uint32 level; /* its tree level */
337 
338 #define SizeOfBtreeNewroot (offsetof(xl_btree_newroot, level) + sizeof(uint32))
339 
340 
341 /*
342  * prototypes for functions in nbtxlog.c
343  */
344 extern void btree_redo(XLogReaderState *record);
345 extern void btree_desc(StringInfo buf, XLogReaderState *record);
346 extern const char *btree_identify(uint8 info);
347 extern void btree_xlog_startup(void);
348 extern void btree_xlog_cleanup(void);
349 extern void btree_mask(char *pagedata, BlockNumber blkno);
350 
351 #endif /* NBTXLOG_H */
uint16 ndeleted
Definition: nbtxlog.h:236
void btree_mask(char *pagedata, BlockNumber blkno)
Definition: nbtxlog.c:1090
bool allequalimage
Definition: nbtxlog.h:57
BlockNumber rootblk
Definition: nbtxlog.h:334
TransactionId latestRemovedXid
Definition: nbtxlog.h:235
void btree_desc(StringInfo buf, XLogReaderState *record)
Definition: nbtdesc.c:20
uint32 last_cleanup_num_delpages
Definition: nbtxlog.h:56
uint16 nintervals
Definition: nbtxlog.h:172
uint32 TransactionId
Definition: c.h:587
struct xl_btree_split xl_btree_split
struct xl_btree_reuse_page xl_btree_reuse_page
struct xl_btree_metadata xl_btree_metadata
BlockNumber root
Definition: nbtxlog.h:52
unsigned char uint8
Definition: c.h:439
FullTransactionId latestRemovedFullXid
Definition: nbtxlog.h:190
uint16 nupdated
Definition: nbtxlog.h:237
RelFileNode node
Definition: nbtxlog.h:188
uint32 level
Definition: nbtxlog.h:335
uint32 BlockNumber
Definition: block.h:31
uint16 nupdated
Definition: nbtxlog.h:224
struct xl_btree_newroot xl_btree_newroot
struct xl_btree_insert xl_btree_insert
uint16 OffsetNumber
Definition: off.h:24
struct xl_btree_delete xl_btree_delete
struct xl_btree_update xl_btree_update
unsigned short uint16
Definition: c.h:440
BlockNumber block
Definition: nbtxlog.h:189
const char * btree_identify(uint8 info)
Definition: nbtdesc.c:124
OffsetNumber newitemoff
Definition: nbtxlog.h:157
struct xl_btree_dedup xl_btree_dedup
struct xl_btree_mark_page_halfdead xl_btree_mark_page_halfdead
static char * buf
Definition: pg_test_fsync.c:68
unsigned int uint32
Definition: c.h:441
struct xl_btree_vacuum xl_btree_vacuum
void btree_xlog_cleanup(void)
Definition: nbtxlog.c:1080
uint32 version
Definition: nbtxlog.h:51
uint16 ndeleted
Definition: nbtxlog.h:223
uint32 level
Definition: nbtxlog.h:155
OffsetNumber offnum
Definition: nbtxlog.h:81
void btree_xlog_startup(void)
Definition: nbtxlog.c:1072
uint32 fastlevel
Definition: nbtxlog.h:55
struct xl_btree_unlink_page xl_btree_unlink_page
uint32 level
Definition: nbtxlog.h:53
BlockNumber fastroot
Definition: nbtxlog.h:54
uint16 postingoff
Definition: nbtxlog.h:158
OffsetNumber firstrightoff
Definition: nbtxlog.h:156
void btree_redo(XLogReaderState *record)
Definition: nbtxlog.c:1013
uint16 ndeletedtids
Definition: nbtxlog.h:254