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htup_details.h
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1 /*-------------------------------------------------------------------------
2  *
3  * htup_details.h
4  * POSTGRES heap tuple header definitions.
5  *
6  *
7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * src/include/access/htup_details.h
11  *
12  *-------------------------------------------------------------------------
13  */
14 #ifndef HTUP_DETAILS_H
15 #define HTUP_DETAILS_H
16 
17 #include "access/htup.h"
18 #include "access/transam.h"
19 #include "access/tupdesc.h"
20 #include "access/tupmacs.h"
21 #include "storage/bufpage.h"
22 
23 /*
24  * MaxTupleAttributeNumber limits the number of (user) columns in a tuple.
25  * The key limit on this value is that the size of the fixed overhead for
26  * a tuple, plus the size of the null-values bitmap (at 1 bit per column),
27  * plus MAXALIGN alignment, must fit into t_hoff which is uint8. On most
28  * machines the upper limit without making t_hoff wider would be a little
29  * over 1700. We use round numbers here and for MaxHeapAttributeNumber
30  * so that alterations in HeapTupleHeaderData layout won't change the
31  * supported max number of columns.
32  */
33 #define MaxTupleAttributeNumber 1664 /* 8 * 208 */
34 
35 /*
36  * MaxHeapAttributeNumber limits the number of (user) columns in a table.
37  * This should be somewhat less than MaxTupleAttributeNumber. It must be
38  * at least one less, else we will fail to do UPDATEs on a maximal-width
39  * table (because UPDATE has to form working tuples that include CTID).
40  * In practice we want some additional daylight so that we can gracefully
41  * support operations that add hidden "resjunk" columns, for example
42  * SELECT * FROM wide_table ORDER BY foo, bar, baz.
43  * In any case, depending on column data types you will likely be running
44  * into the disk-block-based limit on overall tuple size if you have more
45  * than a thousand or so columns. TOAST won't help.
46  */
47 #define MaxHeapAttributeNumber 1600 /* 8 * 200 */
48 
49 /*
50  * Heap tuple header. To avoid wasting space, the fields should be
51  * laid out in such a way as to avoid structure padding.
52  *
53  * Datums of composite types (row types) share the same general structure
54  * as on-disk tuples, so that the same routines can be used to build and
55  * examine them. However the requirements are slightly different: a Datum
56  * does not need any transaction visibility information, and it does need
57  * a length word and some embedded type information. We can achieve this
58  * by overlaying the xmin/cmin/xmax/cmax/xvac fields of a heap tuple
59  * with the fields needed in the Datum case. Typically, all tuples built
60  * in-memory will be initialized with the Datum fields; but when a tuple is
61  * about to be inserted in a table, the transaction fields will be filled,
62  * overwriting the datum fields.
63  *
64  * The overall structure of a heap tuple looks like:
65  * fixed fields (HeapTupleHeaderData struct)
66  * nulls bitmap (if HEAP_HASNULL is set in t_infomask)
67  * alignment padding (as needed to make user data MAXALIGN'd)
68  * object ID (if HEAP_HASOID_OLD is set in t_infomask, not created
69  * anymore)
70  * user data fields
71  *
72  * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three
73  * physical fields. Xmin and Xmax are always really stored, but Cmin, Cmax
74  * and Xvac share a field. This works because we know that Cmin and Cmax
75  * are only interesting for the lifetime of the inserting and deleting
76  * transaction respectively. If a tuple is inserted and deleted in the same
77  * transaction, we store a "combo" command id that can be mapped to the real
78  * cmin and cmax, but only by use of local state within the originating
79  * backend. See combocid.c for more details. Meanwhile, Xvac is only set by
80  * old-style VACUUM FULL, which does not have any command sub-structure and so
81  * does not need either Cmin or Cmax. (This requires that old-style VACUUM
82  * FULL never try to move a tuple whose Cmin or Cmax is still interesting,
83  * ie, an insert-in-progress or delete-in-progress tuple.)
84  *
85  * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
86  * is initialized with its own TID (location). If the tuple is ever updated,
87  * its t_ctid is changed to point to the replacement version of the tuple. Or
88  * if the tuple is moved from one partition to another, due to an update of
89  * the partition key, t_ctid is set to a special value to indicate that
90  * (see ItemPointerSetMovedPartitions). Thus, a tuple is the latest version
91  * of its row iff XMAX is invalid or
92  * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
93  * either locked or deleted). One can follow the chain of t_ctid links
94  * to find the newest version of the row, unless it was moved to a different
95  * partition. Beware however that VACUUM might
96  * erase the pointed-to (newer) tuple before erasing the pointing (older)
97  * tuple. Hence, when following a t_ctid link, it is necessary to check
98  * to see if the referenced slot is empty or contains an unrelated tuple.
99  * Check that the referenced tuple has XMIN equal to the referencing tuple's
100  * XMAX to verify that it is actually the descendant version and not an
101  * unrelated tuple stored into a slot recently freed by VACUUM. If either
102  * check fails, one may assume that there is no live descendant version.
103  *
104  * t_ctid is sometimes used to store a speculative insertion token, instead
105  * of a real TID. A speculative token is set on a tuple that's being
106  * inserted, until the inserter is sure that it wants to go ahead with the
107  * insertion. Hence a token should only be seen on a tuple with an XMAX
108  * that's still in-progress, or invalid/aborted. The token is replaced with
109  * the tuple's real TID when the insertion is confirmed. One should never
110  * see a speculative insertion token while following a chain of t_ctid links,
111  * because they are not used on updates, only insertions.
112  *
113  * Following the fixed header fields, the nulls bitmap is stored (beginning
114  * at t_bits). The bitmap is *not* stored if t_infomask shows that there
115  * are no nulls in the tuple. If an OID field is present (as indicated by
116  * t_infomask), then it is stored just before the user data, which begins at
117  * the offset shown by t_hoff. Note that t_hoff must be a multiple of
118  * MAXALIGN.
119  */
120 
121 typedef struct HeapTupleFields
122 {
123  TransactionId t_xmin; /* inserting xact ID */
124  TransactionId t_xmax; /* deleting or locking xact ID */
125 
126  union
127  {
128  CommandId t_cid; /* inserting or deleting command ID, or both */
129  TransactionId t_xvac; /* old-style VACUUM FULL xact ID */
130  } t_field3;
132 
133 typedef struct DatumTupleFields
134 {
135  int32 datum_len_; /* varlena header (do not touch directly!) */
136 
137  int32 datum_typmod; /* -1, or identifier of a record type */
138 
139  Oid datum_typeid; /* composite type OID, or RECORDOID */
140 
141  /*
142  * datum_typeid cannot be a domain over composite, only plain composite,
143  * even if the datum is meant as a value of a domain-over-composite type.
144  * This is in line with the general principle that CoerceToDomain does not
145  * change the physical representation of the base type value.
146  *
147  * Note: field ordering is chosen with thought that Oid might someday
148  * widen to 64 bits.
149  */
151 
153 {
154  union
155  {
158  } t_choice;
159 
160  ItemPointerData t_ctid; /* current TID of this or newer tuple (or a
161  * speculative insertion token) */
162 
163  /* Fields below here must match MinimalTupleData! */
164 
165 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2
166  uint16 t_infomask2; /* number of attributes + various flags */
167 
168 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3
169  uint16 t_infomask; /* various flag bits, see below */
170 
171 #define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4
172  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
173 
174  /* ^ - 23 bytes - ^ */
175 
176 #define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5
177  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
178 
179  /* MORE DATA FOLLOWS AT END OF STRUCT */
180 };
181 
182 /* typedef appears in htup.h */
183 
184 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
185 
186 /*
187  * information stored in t_infomask:
188  */
189 #define HEAP_HASNULL 0x0001 /* has null attribute(s) */
190 #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
191 #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
192 #define HEAP_HASOID_OLD 0x0008 /* has an object-id field */
193 #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
194 #define HEAP_COMBOCID 0x0020 /* t_cid is a combo CID */
195 #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
196 #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
197 
198  /* xmax is a shared locker */
199 #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
200 
201 #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
202  HEAP_XMAX_KEYSHR_LOCK)
203 #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
204 #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
205 #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
206 #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
207 #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
208 #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
209 #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
210 #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
211  * VACUUM FULL; kept for binary
212  * upgrade support */
213 #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
214  * VACUUM FULL; kept for binary
215  * upgrade support */
216 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
217 
218 #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
219 
220 /*
221  * A tuple is only locked (i.e. not updated by its Xmax) if the
222  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
223  * not a multi and the EXCL_LOCK bit is set.
224  *
225  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
226  * aborted updater transaction.
227  *
228  * Beware of multiple evaluations of the argument.
229  */
230 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
231  (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
232  (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
233 
234 /*
235  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
236  * HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_KEYSHR_LOCK must come from a tuple that was
237  * share-locked in 9.2 or earlier and then pg_upgrade'd.
238  *
239  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
240  * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a
241  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
242  * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and
243  * up, so if we see that combination we know for certain that the tuple was
244  * locked in an earlier release; since all such lockers are gone (they cannot
245  * survive through pg_upgrade), such tuples can safely be considered not
246  * locked.
247  *
248  * We must not resolve such multixacts locally, because the result would be
249  * bogus, regardless of where they stand with respect to the current valid
250  * multixact range.
251  */
252 #define HEAP_LOCKED_UPGRADED(infomask) \
253 ( \
254  ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
255  ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
256  (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
257 )
258 
259 /*
260  * Use these to test whether a particular lock is applied to a tuple
261  */
262 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
263  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
264 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
265  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
266 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
267  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
268 
269 /* turn these all off when Xmax is to change */
270 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
271  HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
272 
273 /*
274  * information stored in t_infomask2:
275  */
276 #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
277 /* bits 0x1800 are available */
278 #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
279  * modified, or tuple deleted */
280 #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
281 #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
282 
283 #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
284 
285 /*
286  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is
287  * only used in tuples that are in the hash table, and those don't need
288  * any visibility information, so we can overlay it on a visibility flag
289  * instead of using up a dedicated bit.
290  */
291 #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
292 
293 /*
294  * HeapTupleHeader accessor macros
295  *
296  * Note: beware of multiple evaluations of "tup" argument. But the Set
297  * macros evaluate their other argument only once.
298  */
299 
300 /*
301  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
302  * originally used to insert the tuple. However, the tuple might actually
303  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
304  * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
305  * the xmin to FrozenTransactionId, and that value may still be encountered
306  * on disk.
307  */
308 #define HeapTupleHeaderGetRawXmin(tup) \
309 ( \
310  (tup)->t_choice.t_heap.t_xmin \
311 )
312 
313 #define HeapTupleHeaderGetXmin(tup) \
314 ( \
315  HeapTupleHeaderXminFrozen(tup) ? \
316  FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
317 )
318 
319 #define HeapTupleHeaderSetXmin(tup, xid) \
320 ( \
321  (tup)->t_choice.t_heap.t_xmin = (xid) \
322 )
323 
324 #define HeapTupleHeaderXminCommitted(tup) \
325 ( \
326  ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
327 )
328 
329 #define HeapTupleHeaderXminInvalid(tup) \
330 ( \
331  ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
332  HEAP_XMIN_INVALID \
333 )
334 
335 #define HeapTupleHeaderXminFrozen(tup) \
336 ( \
337  ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
338 )
339 
340 #define HeapTupleHeaderSetXminCommitted(tup) \
341 ( \
342  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
343  ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
344 )
345 
346 #define HeapTupleHeaderSetXminInvalid(tup) \
347 ( \
348  AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
349  ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
350 )
351 
352 #define HeapTupleHeaderSetXminFrozen(tup) \
353 ( \
354  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
355  ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
356 )
357 
358 /*
359  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid
360  * that updated a tuple, you might need to resolve the MultiXactId if certain
361  * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care
362  * to resolve the MultiXactId if necessary. This might involve multixact I/O,
363  * so it should only be used if absolutely necessary.
364  */
365 #define HeapTupleHeaderGetUpdateXid(tup) \
366 ( \
367  (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
368  ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
369  !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
370  HeapTupleGetUpdateXid(tup) \
371  : \
372  HeapTupleHeaderGetRawXmax(tup) \
373 )
374 
375 #define HeapTupleHeaderGetRawXmax(tup) \
376 ( \
377  (tup)->t_choice.t_heap.t_xmax \
378 )
379 
380 #define HeapTupleHeaderSetXmax(tup, xid) \
381 ( \
382  (tup)->t_choice.t_heap.t_xmax = (xid) \
383 )
384 
385 /*
386  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
387  * it is useful or not. Most code should use HeapTupleHeaderGetCmin or
388  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
389  * get a legitimate result, ie you are in the originating transaction!
390  */
391 #define HeapTupleHeaderGetRawCommandId(tup) \
392 ( \
393  (tup)->t_choice.t_heap.t_field3.t_cid \
394 )
395 
396 /* SetCmin is reasonably simple since we never need a combo CID */
397 #define HeapTupleHeaderSetCmin(tup, cid) \
398 do { \
399  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
400  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
401  (tup)->t_infomask &= ~HEAP_COMBOCID; \
402 } while (0)
403 
404 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
405 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
406 do { \
407  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
408  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
409  if (iscombo) \
410  (tup)->t_infomask |= HEAP_COMBOCID; \
411  else \
412  (tup)->t_infomask &= ~HEAP_COMBOCID; \
413 } while (0)
414 
415 #define HeapTupleHeaderGetXvac(tup) \
416 ( \
417  ((tup)->t_infomask & HEAP_MOVED) ? \
418  (tup)->t_choice.t_heap.t_field3.t_xvac \
419  : \
420  InvalidTransactionId \
421 )
422 
423 #define HeapTupleHeaderSetXvac(tup, xid) \
424 do { \
425  Assert((tup)->t_infomask & HEAP_MOVED); \
426  (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
427 } while (0)
428 
429 #define HeapTupleHeaderIsSpeculative(tup) \
430 ( \
431  (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \
432 )
433 
434 #define HeapTupleHeaderGetSpeculativeToken(tup) \
435 ( \
436  AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
437  ItemPointerGetBlockNumber(&(tup)->t_ctid) \
438 )
439 
440 #define HeapTupleHeaderSetSpeculativeToken(tup, token) \
441 ( \
442  ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
443 )
444 
445 #define HeapTupleHeaderIndicatesMovedPartitions(tup) \
446  ItemPointerIndicatesMovedPartitions(&(tup)->t_ctid)
447 
448 #define HeapTupleHeaderSetMovedPartitions(tup) \
449  ItemPointerSetMovedPartitions(&(tup)->t_ctid)
450 
451 #define HeapTupleHeaderGetDatumLength(tup) \
452  VARSIZE(tup)
453 
454 #define HeapTupleHeaderSetDatumLength(tup, len) \
455  SET_VARSIZE(tup, len)
456 
457 #define HeapTupleHeaderGetTypeId(tup) \
458 ( \
459  (tup)->t_choice.t_datum.datum_typeid \
460 )
461 
462 #define HeapTupleHeaderSetTypeId(tup, typeid) \
463 ( \
464  (tup)->t_choice.t_datum.datum_typeid = (typeid) \
465 )
466 
467 #define HeapTupleHeaderGetTypMod(tup) \
468 ( \
469  (tup)->t_choice.t_datum.datum_typmod \
470 )
471 
472 #define HeapTupleHeaderSetTypMod(tup, typmod) \
473 ( \
474  (tup)->t_choice.t_datum.datum_typmod = (typmod) \
475 )
476 
477 /*
478  * Note that we stop considering a tuple HOT-updated as soon as it is known
479  * aborted or the would-be updating transaction is known aborted. For best
480  * efficiency, check tuple visibility before using this macro, so that the
481  * INVALID bits will be as up to date as possible.
482  */
483 #define HeapTupleHeaderIsHotUpdated(tup) \
484 ( \
485  ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
486  ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
487  !HeapTupleHeaderXminInvalid(tup) \
488 )
489 
490 #define HeapTupleHeaderSetHotUpdated(tup) \
491 ( \
492  (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
493 )
494 
495 #define HeapTupleHeaderClearHotUpdated(tup) \
496 ( \
497  (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
498 )
499 
500 #define HeapTupleHeaderIsHeapOnly(tup) \
501 ( \
502  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
503 )
504 
505 #define HeapTupleHeaderSetHeapOnly(tup) \
506 ( \
507  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
508 )
509 
510 #define HeapTupleHeaderClearHeapOnly(tup) \
511 ( \
512  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
513 )
514 
515 #define HeapTupleHeaderHasMatch(tup) \
516 ( \
517  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
518 )
519 
520 #define HeapTupleHeaderSetMatch(tup) \
521 ( \
522  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
523 )
524 
525 #define HeapTupleHeaderClearMatch(tup) \
526 ( \
527  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
528 )
529 
530 #define HeapTupleHeaderGetNatts(tup) \
531  ((tup)->t_infomask2 & HEAP_NATTS_MASK)
532 
533 #define HeapTupleHeaderSetNatts(tup, natts) \
534 ( \
535  (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
536 )
537 
538 #define HeapTupleHeaderHasExternal(tup) \
539  (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
540 
541 
542 /*
543  * BITMAPLEN(NATTS) -
544  * Computes size of null bitmap given number of data columns.
545  */
546 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
547 
548 /*
549  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
550  * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the
551  * other stuff that has to be on a disk page. Since heap pages use no
552  * "special space", there's no deduction for that.
553  *
554  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
555  * an otherwise-empty page can indeed hold a tuple of this size. Because
556  * ItemIds and tuples have different alignment requirements, don't assume that
557  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
558  */
559 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
560 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader)
561 
562 /*
563  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
564  * fit on one heap page. (Note that indexes could have more, because they
565  * use a smaller tuple header.) We arrive at the divisor because each tuple
566  * must be maxaligned, and it must have an associated line pointer.
567  *
568  * Note: with HOT, there could theoretically be more line pointers (not actual
569  * tuples) than this on a heap page. However we constrain the number of line
570  * pointers to this anyway, to avoid excessive line-pointer bloat and not
571  * require increases in the size of work arrays.
572  */
573 #define MaxHeapTuplesPerPage \
574  ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
575  (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
576 
577 /*
578  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
579  * data fields of char(n) and similar types. It need not have anything
580  * directly to do with the *actual* upper limit of varlena values, which
581  * is currently 1Gb (see TOAST structures in postgres.h). I've set it
582  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
583  */
584 #define MaxAttrSize (10 * 1024 * 1024)
585 
586 
587 /*
588  * MinimalTuple is an alternative representation that is used for transient
589  * tuples inside the executor, in places where transaction status information
590  * is not required, the tuple rowtype is known, and shaving off a few bytes
591  * is worthwhile because we need to store many tuples. The representation
592  * is chosen so that tuple access routines can work with either full or
593  * minimal tuples via a HeapTupleData pointer structure. The access routines
594  * see no difference, except that they must not access the transaction status
595  * or t_ctid fields because those aren't there.
596  *
597  * For the most part, MinimalTuples should be accessed via TupleTableSlot
598  * routines. These routines will prevent access to the "system columns"
599  * and thereby prevent accidental use of the nonexistent fields.
600  *
601  * MinimalTupleData contains a length word, some padding, and fields matching
602  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
603  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
604  * structs. This makes data alignment rules equivalent in both cases.
605  *
606  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
607  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
608  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
609  * data would start. This trick is what makes the structs seem equivalent.
610  *
611  * Note that t_hoff is computed the same as in a full tuple, hence it includes
612  * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
613  *
614  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
615  * other than the length word. tuplesort.c and tuplestore.c use this to avoid
616  * writing the padding to disk.
617  */
618 #define MINIMAL_TUPLE_OFFSET \
619  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
620 #define MINIMAL_TUPLE_PADDING \
621  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
622 #define MINIMAL_TUPLE_DATA_OFFSET \
623  offsetof(MinimalTupleData, t_infomask2)
624 
626 {
627  uint32 t_len; /* actual length of minimal tuple */
628 
629  char mt_padding[MINIMAL_TUPLE_PADDING];
630 
631  /* Fields below here must match HeapTupleHeaderData! */
632 
633  uint16 t_infomask2; /* number of attributes + various flags */
634 
635  uint16 t_infomask; /* various flag bits, see below */
636 
637  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
638 
639  /* ^ - 23 bytes - ^ */
640 
641  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
642 
643  /* MORE DATA FOLLOWS AT END OF STRUCT */
644 };
645 
646 /* typedef appears in htup.h */
647 
648 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
649 
650 
651 /*
652  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
653  */
654 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
655 
656 /*
657  * Accessor macros to be used with HeapTuple pointers.
658  */
659 
660 #define HeapTupleHasNulls(tuple) \
661  (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
662 
663 #define HeapTupleNoNulls(tuple) \
664  (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
665 
666 #define HeapTupleHasVarWidth(tuple) \
667  (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
668 
669 #define HeapTupleAllFixed(tuple) \
670  (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
671 
672 #define HeapTupleHasExternal(tuple) \
673  (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
674 
675 #define HeapTupleIsHotUpdated(tuple) \
676  HeapTupleHeaderIsHotUpdated((tuple)->t_data)
677 
678 #define HeapTupleSetHotUpdated(tuple) \
679  HeapTupleHeaderSetHotUpdated((tuple)->t_data)
680 
681 #define HeapTupleClearHotUpdated(tuple) \
682  HeapTupleHeaderClearHotUpdated((tuple)->t_data)
683 
684 #define HeapTupleIsHeapOnly(tuple) \
685  HeapTupleHeaderIsHeapOnly((tuple)->t_data)
686 
687 #define HeapTupleSetHeapOnly(tuple) \
688  HeapTupleHeaderSetHeapOnly((tuple)->t_data)
689 
690 #define HeapTupleClearHeapOnly(tuple) \
691  HeapTupleHeaderClearHeapOnly((tuple)->t_data)
692 
693 
694 /* ----------------
695  * fastgetattr
696  *
697  * Fetch a user attribute's value as a Datum (might be either a
698  * value, or a pointer into the data area of the tuple).
699  *
700  * This must not be used when a system attribute might be requested.
701  * Furthermore, the passed attnum MUST be valid. Use heap_getattr()
702  * instead, if in doubt.
703  *
704  * This gets called many times, so we macro the cacheable and NULL
705  * lookups, and call nocachegetattr() for the rest.
706  * ----------------
707  */
708 
709 #if !defined(DISABLE_COMPLEX_MACRO)
710 
711 #define fastgetattr(tup, attnum, tupleDesc, isnull) \
712 ( \
713  AssertMacro((attnum) > 0), \
714  (*(isnull) = false), \
715  HeapTupleNoNulls(tup) ? \
716  ( \
717  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \
718  ( \
719  fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \
720  (char *) (tup)->t_data + (tup)->t_data->t_hoff + \
721  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\
722  ) \
723  : \
724  nocachegetattr((tup), (attnum), (tupleDesc)) \
725  ) \
726  : \
727  ( \
728  att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \
729  ( \
730  (*(isnull) = true), \
731  (Datum)NULL \
732  ) \
733  : \
734  ( \
735  nocachegetattr((tup), (attnum), (tupleDesc)) \
736  ) \
737  ) \
738 )
739 #else /* defined(DISABLE_COMPLEX_MACRO) */
740 
741 extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
742  bool *isnull);
743 #endif /* defined(DISABLE_COMPLEX_MACRO) */
744 
745 
746 /* ----------------
747  * heap_getattr
748  *
749  * Extract an attribute of a heap tuple and return it as a Datum.
750  * This works for either system or user attributes. The given attnum
751  * is properly range-checked.
752  *
753  * If the field in question has a NULL value, we return a zero Datum
754  * and set *isnull == true. Otherwise, we set *isnull == false.
755  *
756  * <tup> is the pointer to the heap tuple. <attnum> is the attribute
757  * number of the column (field) caller wants. <tupleDesc> is a
758  * pointer to the structure describing the row and all its fields.
759  * ----------------
760  */
761 #define heap_getattr(tup, attnum, tupleDesc, isnull) \
762  ( \
763  ((attnum) > 0) ? \
764  ( \
765  ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
766  getmissingattr((tupleDesc), (attnum), (isnull)) \
767  : \
768  fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \
769  ) \
770  : \
771  heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \
772  )
773 
774 
775 /* prototypes for functions in common/heaptuple.c */
776 extern Size heap_compute_data_size(TupleDesc tupleDesc,
777  Datum *values, bool *isnull);
778 extern void heap_fill_tuple(TupleDesc tupleDesc,
779  Datum *values, bool *isnull,
780  char *data, Size data_size,
781  uint16 *infomask, bits8 *bit);
782 extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);
783 extern Datum nocachegetattr(HeapTuple tup, int attnum,
784  TupleDesc att);
785 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
786  bool *isnull);
787 extern Datum getmissingattr(TupleDesc tupleDesc,
788  int attnum, bool *isnull);
789 extern HeapTuple heap_copytuple(HeapTuple tuple);
791 extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);
792 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
793  Datum *values, bool *isnull);
795  TupleDesc tupleDesc,
796  Datum *replValues,
797  bool *replIsnull,
798  bool *doReplace);
800  TupleDesc tupleDesc,
801  int nCols,
802  int *replCols,
803  Datum *replValues,
804  bool *replIsnull);
805 extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
806  Datum *values, bool *isnull);
807 extern void heap_freetuple(HeapTuple htup);
808 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
809  Datum *values, bool *isnull);
810 extern void heap_free_minimal_tuple(MinimalTuple mtup);
814 extern size_t varsize_any(void *p);
815 extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
816 extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
817 
818 #endif /* HTUP_DETAILS_H */
uint32 CommandId
Definition: c.h:601
#define fastgetattr(tup, attnum, tupleDesc, isnull)
Definition: htup_details.h:711
HeapTupleFields t_heap
Definition: htup_details.h:156
union HeapTupleFields::@42 t_field3
uint32 TransactionId
Definition: c.h:587
Size heap_compute_data_size(TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:119
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1338
unsigned char uint8
Definition: c.h:439
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1458
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:706
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:350
struct DatumTupleFields DatumTupleFields
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:627
size_t varsize_any(void *p)
Definition: heaptuple.c:1498
unsigned int Oid
Definition: postgres_ext.h:31
DatumTupleFields t_datum
Definition: htup_details.h:157
signed int int32
Definition: c.h:429
TransactionId t_xmax
Definition: htup_details.h:124
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1427
Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull)
Definition: heaptuple.c:84
unsigned short uint16
Definition: c.h:440
HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *replValues, bool *replIsnull, bool *doReplace)
Definition: heaptuple.c:1113
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1480
ItemPointerData t_ctid
Definition: htup_details.h:160
unsigned int uint32
Definition: c.h:441
TransactionId t_xmin
Definition: htup_details.h:123
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:620
uint8 bits8
Definition: c.h:448
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1356
struct HeapTupleFields HeapTupleFields
bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:359
uintptr_t Datum
Definition: postgres.h:411
TransactionId t_xvac
Definition: htup_details.h:129
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:1249
int16 attnum
Definition: pg_attribute.h:83
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1020
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1439
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:680
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull)
Definition: heaptuple.c:1181
MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:957
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:391
size_t Size
Definition: c.h:540
HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:969
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att)
Definition: heaptuple.c:423
static Datum values[MAXATTR]
Definition: bootstrap.c:166
void heap_fill_tuple(TupleDesc tupleDesc, Datum *values, bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit)
Definition: heaptuple.c:304
CommandId t_cid
Definition: htup_details.h:128
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:984