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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) 1996-2024, 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 #include "varatt.h"
23 
24 /*
25  * MaxTupleAttributeNumber limits the number of (user) columns in a tuple.
26  * The key limit on this value is that the size of the fixed overhead for
27  * a tuple, plus the size of the null-values bitmap (at 1 bit per column),
28  * plus MAXALIGN alignment, must fit into t_hoff which is uint8. On most
29  * machines the upper limit without making t_hoff wider would be a little
30  * over 1700. We use round numbers here and for MaxHeapAttributeNumber
31  * so that alterations in HeapTupleHeaderData layout won't change the
32  * supported max number of columns.
33  */
34 #define MaxTupleAttributeNumber 1664 /* 8 * 208 */
35 
36 /*
37  * MaxHeapAttributeNumber limits the number of (user) columns in a table.
38  * This should be somewhat less than MaxTupleAttributeNumber. It must be
39  * at least one less, else we will fail to do UPDATEs on a maximal-width
40  * table (because UPDATE has to form working tuples that include CTID).
41  * In practice we want some additional daylight so that we can gracefully
42  * support operations that add hidden "resjunk" columns, for example
43  * SELECT * FROM wide_table ORDER BY foo, bar, baz.
44  * In any case, depending on column data types you will likely be running
45  * into the disk-block-based limit on overall tuple size if you have more
46  * than a thousand or so columns. TOAST won't help.
47  */
48 #define MaxHeapAttributeNumber 1600 /* 8 * 200 */
49 
50 /*
51  * Heap tuple header. To avoid wasting space, the fields should be
52  * laid out in such a way as to avoid structure padding.
53  *
54  * Datums of composite types (row types) share the same general structure
55  * as on-disk tuples, so that the same routines can be used to build and
56  * examine them. However the requirements are slightly different: a Datum
57  * does not need any transaction visibility information, and it does need
58  * a length word and some embedded type information. We can achieve this
59  * by overlaying the xmin/cmin/xmax/cmax/xvac fields of a heap tuple
60  * with the fields needed in the Datum case. Typically, all tuples built
61  * in-memory will be initialized with the Datum fields; but when a tuple is
62  * about to be inserted in a table, the transaction fields will be filled,
63  * overwriting the datum fields.
64  *
65  * The overall structure of a heap tuple looks like:
66  * fixed fields (HeapTupleHeaderData struct)
67  * nulls bitmap (if HEAP_HASNULL is set in t_infomask)
68  * alignment padding (as needed to make user data MAXALIGN'd)
69  * object ID (if HEAP_HASOID_OLD is set in t_infomask, not created
70  * anymore)
71  * user data fields
72  *
73  * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three
74  * physical fields. Xmin and Xmax are always really stored, but Cmin, Cmax
75  * and Xvac share a field. This works because we know that Cmin and Cmax
76  * are only interesting for the lifetime of the inserting and deleting
77  * transaction respectively. If a tuple is inserted and deleted in the same
78  * transaction, we store a "combo" command id that can be mapped to the real
79  * cmin and cmax, but only by use of local state within the originating
80  * backend. See combocid.c for more details. Meanwhile, Xvac is only set by
81  * old-style VACUUM FULL, which does not have any command sub-structure and so
82  * does not need either Cmin or Cmax. (This requires that old-style VACUUM
83  * FULL never try to move a tuple whose Cmin or Cmax is still interesting,
84  * ie, an insert-in-progress or delete-in-progress tuple.)
85  *
86  * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
87  * is initialized with its own TID (location). If the tuple is ever updated,
88  * its t_ctid is changed to point to the replacement version of the tuple. Or
89  * if the tuple is moved from one partition to another, due to an update of
90  * the partition key, t_ctid is set to a special value to indicate that
91  * (see ItemPointerSetMovedPartitions). Thus, a tuple is the latest version
92  * of its row iff XMAX is invalid or
93  * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
94  * either locked or deleted). One can follow the chain of t_ctid links
95  * to find the newest version of the row, unless it was moved to a different
96  * partition. Beware however that VACUUM might
97  * erase the pointed-to (newer) tuple before erasing the pointing (older)
98  * tuple. Hence, when following a t_ctid link, it is necessary to check
99  * to see if the referenced slot is empty or contains an unrelated tuple.
100  * Check that the referenced tuple has XMIN equal to the referencing tuple's
101  * XMAX to verify that it is actually the descendant version and not an
102  * unrelated tuple stored into a slot recently freed by VACUUM. If either
103  * check fails, one may assume that there is no live descendant version.
104  *
105  * t_ctid is sometimes used to store a speculative insertion token, instead
106  * of a real TID. A speculative token is set on a tuple that's being
107  * inserted, until the inserter is sure that it wants to go ahead with the
108  * insertion. Hence a token should only be seen on a tuple with an XMAX
109  * that's still in-progress, or invalid/aborted. The token is replaced with
110  * the tuple's real TID when the insertion is confirmed. One should never
111  * see a speculative insertion token while following a chain of t_ctid links,
112  * because they are not used on updates, only insertions.
113  *
114  * Following the fixed header fields, the nulls bitmap is stored (beginning
115  * at t_bits). The bitmap is *not* stored if t_infomask shows that there
116  * are no nulls in the tuple. If an OID field is present (as indicated by
117  * t_infomask), then it is stored just before the user data, which begins at
118  * the offset shown by t_hoff. Note that t_hoff must be a multiple of
119  * MAXALIGN.
120  */
121 
122 typedef struct HeapTupleFields
123 {
124  TransactionId t_xmin; /* inserting xact ID */
125  TransactionId t_xmax; /* deleting or locking xact ID */
126 
127  union
128  {
129  CommandId t_cid; /* inserting or deleting command ID, or both */
130  TransactionId t_xvac; /* old-style VACUUM FULL xact ID */
133 
134 typedef struct DatumTupleFields
135 {
136  int32 datum_len_; /* varlena header (do not touch directly!) */
137 
138  int32 datum_typmod; /* -1, or identifier of a record type */
139 
140  Oid datum_typeid; /* composite type OID, or RECORDOID */
141 
142  /*
143  * datum_typeid cannot be a domain over composite, only plain composite,
144  * even if the datum is meant as a value of a domain-over-composite type.
145  * This is in line with the general principle that CoerceToDomain does not
146  * change the physical representation of the base type value.
147  *
148  * Note: field ordering is chosen with thought that Oid might someday
149  * widen to 64 bits.
150  */
152 
154 {
155  union
156  {
160 
161  ItemPointerData t_ctid; /* current TID of this or newer tuple (or a
162  * speculative insertion token) */
163 
164  /* Fields below here must match MinimalTupleData! */
165 
166 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2
167  uint16 t_infomask2; /* number of attributes + various flags */
168 
169 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3
170  uint16 t_infomask; /* various flag bits, see below */
171 
172 #define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4
173  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
174 
175  /* ^ - 23 bytes - ^ */
176 
177 #define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5
178  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
179 
180  /* MORE DATA FOLLOWS AT END OF STRUCT */
181 };
182 
183 /* typedef appears in htup.h */
184 
185 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
186 
187 /*
188  * information stored in t_infomask:
189  */
190 #define HEAP_HASNULL 0x0001 /* has null attribute(s) */
191 #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
192 #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
193 #define HEAP_HASOID_OLD 0x0008 /* has an object-id field */
194 #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
195 #define HEAP_COMBOCID 0x0020 /* t_cid is a combo CID */
196 #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
197 #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
198 
199  /* xmax is a shared locker */
200 #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
201 
202 #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
203  HEAP_XMAX_KEYSHR_LOCK)
204 #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
205 #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
206 #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
207 #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
208 #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
209 #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
210 #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
211 #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
212  * VACUUM FULL; kept for binary
213  * upgrade support */
214 #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
215  * VACUUM FULL; kept for binary
216  * upgrade support */
217 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
218 
219 #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
220 
221 /*
222  * A tuple is only locked (i.e. not updated by its Xmax) if the
223  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
224  * not a multi and the EXCL_LOCK bit is set.
225  *
226  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
227  * aborted updater transaction.
228  *
229  * Beware of multiple evaluations of the argument.
230  */
231 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
232  (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
233  (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
234 
235 /*
236  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
237  * HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_KEYSHR_LOCK must come from a tuple that was
238  * share-locked in 9.2 or earlier and then pg_upgrade'd.
239  *
240  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
241  * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a
242  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
243  * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and
244  * up, so if we see that combination we know for certain that the tuple was
245  * locked in an earlier release; since all such lockers are gone (they cannot
246  * survive through pg_upgrade), such tuples can safely be considered not
247  * locked.
248  *
249  * We must not resolve such multixacts locally, because the result would be
250  * bogus, regardless of where they stand with respect to the current valid
251  * multixact range.
252  */
253 #define HEAP_LOCKED_UPGRADED(infomask) \
254 ( \
255  ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
256  ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
257  (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
258 )
259 
260 /*
261  * Use these to test whether a particular lock is applied to a tuple
262  */
263 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
264  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
265 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
266  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
267 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
268  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
269 
270 /* turn these all off when Xmax is to change */
271 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
272  HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
273 
274 /*
275  * information stored in t_infomask2:
276  */
277 #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
278 /* bits 0x1800 are available */
279 #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
280  * modified, or tuple deleted */
281 #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
282 #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
283 
284 #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
285 
286 /*
287  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is
288  * only used in tuples that are in the hash table, and those don't need
289  * any visibility information, so we can overlay it on a visibility flag
290  * instead of using up a dedicated bit.
291  */
292 #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
293 
294 /*
295  * HeapTupleHeader accessor macros
296  *
297  * Note: beware of multiple evaluations of "tup" argument. But the Set
298  * macros evaluate their other argument only once.
299  */
300 
301 /*
302  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
303  * originally used to insert the tuple. However, the tuple might actually
304  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
305  * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
306  * the xmin to FrozenTransactionId, and that value may still be encountered
307  * on disk.
308  */
309 #define HeapTupleHeaderGetRawXmin(tup) \
310 ( \
311  (tup)->t_choice.t_heap.t_xmin \
312 )
313 
314 #define HeapTupleHeaderGetXmin(tup) \
315 ( \
316  HeapTupleHeaderXminFrozen(tup) ? \
317  FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
318 )
319 
320 #define HeapTupleHeaderSetXmin(tup, xid) \
321 ( \
322  (tup)->t_choice.t_heap.t_xmin = (xid) \
323 )
324 
325 #define HeapTupleHeaderXminCommitted(tup) \
326 ( \
327  ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
328 )
329 
330 #define HeapTupleHeaderXminInvalid(tup) \
331 ( \
332  ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
333  HEAP_XMIN_INVALID \
334 )
335 
336 #define HeapTupleHeaderXminFrozen(tup) \
337 ( \
338  ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
339 )
340 
341 #define HeapTupleHeaderSetXminCommitted(tup) \
342 ( \
343  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
344  ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
345 )
346 
347 #define HeapTupleHeaderSetXminInvalid(tup) \
348 ( \
349  AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
350  ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
351 )
352 
353 #define HeapTupleHeaderSetXminFrozen(tup) \
354 ( \
355  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
356  ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
357 )
358 
359 /*
360  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid
361  * that updated a tuple, you might need to resolve the MultiXactId if certain
362  * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care
363  * to resolve the MultiXactId if necessary. This might involve multixact I/O,
364  * so it should only be used if absolutely necessary.
365  */
366 #define HeapTupleHeaderGetUpdateXid(tup) \
367 ( \
368  (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
369  ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
370  !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
371  HeapTupleGetUpdateXid(tup) \
372  : \
373  HeapTupleHeaderGetRawXmax(tup) \
374 )
375 
376 #define HeapTupleHeaderGetRawXmax(tup) \
377 ( \
378  (tup)->t_choice.t_heap.t_xmax \
379 )
380 
381 #define HeapTupleHeaderSetXmax(tup, xid) \
382 ( \
383  (tup)->t_choice.t_heap.t_xmax = (xid) \
384 )
385 
386 /*
387  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
388  * it is useful or not. Most code should use HeapTupleHeaderGetCmin or
389  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
390  * get a legitimate result, ie you are in the originating transaction!
391  */
392 #define HeapTupleHeaderGetRawCommandId(tup) \
393 ( \
394  (tup)->t_choice.t_heap.t_field3.t_cid \
395 )
396 
397 /* SetCmin is reasonably simple since we never need a combo CID */
398 #define HeapTupleHeaderSetCmin(tup, cid) \
399 do { \
400  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
401  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
402  (tup)->t_infomask &= ~HEAP_COMBOCID; \
403 } while (0)
404 
405 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
406 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
407 do { \
408  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
409  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
410  if (iscombo) \
411  (tup)->t_infomask |= HEAP_COMBOCID; \
412  else \
413  (tup)->t_infomask &= ~HEAP_COMBOCID; \
414 } while (0)
415 
416 #define HeapTupleHeaderGetXvac(tup) \
417 ( \
418  ((tup)->t_infomask & HEAP_MOVED) ? \
419  (tup)->t_choice.t_heap.t_field3.t_xvac \
420  : \
421  InvalidTransactionId \
422 )
423 
424 #define HeapTupleHeaderSetXvac(tup, xid) \
425 do { \
426  Assert((tup)->t_infomask & HEAP_MOVED); \
427  (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
428 } while (0)
429 
431  "invalid speculative token constant");
432 
433 #define HeapTupleHeaderIsSpeculative(tup) \
434 ( \
435  (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \
436 )
437 
438 #define HeapTupleHeaderGetSpeculativeToken(tup) \
439 ( \
440  AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
441  ItemPointerGetBlockNumber(&(tup)->t_ctid) \
442 )
443 
444 #define HeapTupleHeaderSetSpeculativeToken(tup, token) \
445 ( \
446  ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
447 )
448 
449 #define HeapTupleHeaderIndicatesMovedPartitions(tup) \
450  ItemPointerIndicatesMovedPartitions(&(tup)->t_ctid)
451 
452 #define HeapTupleHeaderSetMovedPartitions(tup) \
453  ItemPointerSetMovedPartitions(&(tup)->t_ctid)
454 
455 #define HeapTupleHeaderGetDatumLength(tup) \
456  VARSIZE(tup)
457 
458 #define HeapTupleHeaderSetDatumLength(tup, len) \
459  SET_VARSIZE(tup, len)
460 
461 #define HeapTupleHeaderGetTypeId(tup) \
462 ( \
463  (tup)->t_choice.t_datum.datum_typeid \
464 )
465 
466 #define HeapTupleHeaderSetTypeId(tup, typeid) \
467 ( \
468  (tup)->t_choice.t_datum.datum_typeid = (typeid) \
469 )
470 
471 #define HeapTupleHeaderGetTypMod(tup) \
472 ( \
473  (tup)->t_choice.t_datum.datum_typmod \
474 )
475 
476 #define HeapTupleHeaderSetTypMod(tup, typmod) \
477 ( \
478  (tup)->t_choice.t_datum.datum_typmod = (typmod) \
479 )
480 
481 /*
482  * Note that we stop considering a tuple HOT-updated as soon as it is known
483  * aborted or the would-be updating transaction is known aborted. For best
484  * efficiency, check tuple visibility before using this macro, so that the
485  * INVALID bits will be as up to date as possible.
486  */
487 #define HeapTupleHeaderIsHotUpdated(tup) \
488 ( \
489  ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
490  ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
491  !HeapTupleHeaderXminInvalid(tup) \
492 )
493 
494 #define HeapTupleHeaderSetHotUpdated(tup) \
495 ( \
496  (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
497 )
498 
499 #define HeapTupleHeaderClearHotUpdated(tup) \
500 ( \
501  (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
502 )
503 
504 #define HeapTupleHeaderIsHeapOnly(tup) \
505 ( \
506  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
507 )
508 
509 #define HeapTupleHeaderSetHeapOnly(tup) \
510 ( \
511  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
512 )
513 
514 #define HeapTupleHeaderClearHeapOnly(tup) \
515 ( \
516  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
517 )
518 
519 #define HeapTupleHeaderHasMatch(tup) \
520 ( \
521  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
522 )
523 
524 #define HeapTupleHeaderSetMatch(tup) \
525 ( \
526  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
527 )
528 
529 #define HeapTupleHeaderClearMatch(tup) \
530 ( \
531  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
532 )
533 
534 #define HeapTupleHeaderGetNatts(tup) \
535  ((tup)->t_infomask2 & HEAP_NATTS_MASK)
536 
537 #define HeapTupleHeaderSetNatts(tup, natts) \
538 ( \
539  (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
540 )
541 
542 #define HeapTupleHeaderHasExternal(tup) \
543  (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
544 
545 
546 /*
547  * BITMAPLEN(NATTS) -
548  * Computes size of null bitmap given number of data columns.
549  */
550 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
551 
552 /*
553  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
554  * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the
555  * other stuff that has to be on a disk page. Since heap pages use no
556  * "special space", there's no deduction for that.
557  *
558  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
559  * an otherwise-empty page can indeed hold a tuple of this size. Because
560  * ItemIds and tuples have different alignment requirements, don't assume that
561  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
562  */
563 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
564 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader)
565 
566 /*
567  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
568  * fit on one heap page. (Note that indexes could have more, because they
569  * use a smaller tuple header.) We arrive at the divisor because each tuple
570  * must be maxaligned, and it must have an associated line pointer.
571  *
572  * Note: with HOT, there could theoretically be more line pointers (not actual
573  * tuples) than this on a heap page. However we constrain the number of line
574  * pointers to this anyway, to avoid excessive line-pointer bloat and not
575  * require increases in the size of work arrays.
576  */
577 #define MaxHeapTuplesPerPage \
578  ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
579  (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
580 
581 /*
582  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
583  * data fields of char(n) and similar types. It need not have anything
584  * directly to do with the *actual* upper limit of varlena values, which
585  * is currently 1Gb (see TOAST structures in postgres.h). I've set it
586  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
587  */
588 #define MaxAttrSize (10 * 1024 * 1024)
589 
590 
591 /*
592  * MinimalTuple is an alternative representation that is used for transient
593  * tuples inside the executor, in places where transaction status information
594  * is not required, the tuple rowtype is known, and shaving off a few bytes
595  * is worthwhile because we need to store many tuples. The representation
596  * is chosen so that tuple access routines can work with either full or
597  * minimal tuples via a HeapTupleData pointer structure. The access routines
598  * see no difference, except that they must not access the transaction status
599  * or t_ctid fields because those aren't there.
600  *
601  * For the most part, MinimalTuples should be accessed via TupleTableSlot
602  * routines. These routines will prevent access to the "system columns"
603  * and thereby prevent accidental use of the nonexistent fields.
604  *
605  * MinimalTupleData contains a length word, some padding, and fields matching
606  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
607  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
608  * structs. This makes data alignment rules equivalent in both cases.
609  *
610  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
611  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
612  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
613  * data would start. This trick is what makes the structs seem equivalent.
614  *
615  * Note that t_hoff is computed the same as in a full tuple, hence it includes
616  * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
617  *
618  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
619  * other than the length word. tuplesort.c and tuplestore.c use this to avoid
620  * writing the padding to disk.
621  */
622 #define MINIMAL_TUPLE_OFFSET \
623  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
624 #define MINIMAL_TUPLE_PADDING \
625  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
626 #define MINIMAL_TUPLE_DATA_OFFSET \
627  offsetof(MinimalTupleData, t_infomask2)
628 
629 struct MinimalTupleData
630 {
631  uint32 t_len; /* actual length of minimal tuple */
632 
634 
635  /* Fields below here must match HeapTupleHeaderData! */
636 
637  uint16 t_infomask2; /* number of attributes + various flags */
638 
639  uint16 t_infomask; /* various flag bits, see below */
640 
641  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
642 
643  /* ^ - 23 bytes - ^ */
644 
645  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
646 
647  /* MORE DATA FOLLOWS AT END OF STRUCT */
648 };
649 
650 /* typedef appears in htup.h */
651 
652 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
653 
654 
655 /*
656  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
657  */
658 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
659 
660 /*
661  * Accessor macros to be used with HeapTuple pointers.
662  */
663 
664 #define HeapTupleHasNulls(tuple) \
665  (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
666 
667 #define HeapTupleNoNulls(tuple) \
668  (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
669 
670 #define HeapTupleHasVarWidth(tuple) \
671  (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
672 
673 #define HeapTupleAllFixed(tuple) \
674  (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
675 
676 #define HeapTupleHasExternal(tuple) \
677  (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
678 
679 #define HeapTupleIsHotUpdated(tuple) \
680  HeapTupleHeaderIsHotUpdated((tuple)->t_data)
681 
682 #define HeapTupleSetHotUpdated(tuple) \
683  HeapTupleHeaderSetHotUpdated((tuple)->t_data)
684 
685 #define HeapTupleClearHotUpdated(tuple) \
686  HeapTupleHeaderClearHotUpdated((tuple)->t_data)
687 
688 #define HeapTupleIsHeapOnly(tuple) \
689  HeapTupleHeaderIsHeapOnly((tuple)->t_data)
690 
691 #define HeapTupleSetHeapOnly(tuple) \
692  HeapTupleHeaderSetHeapOnly((tuple)->t_data)
693 
694 #define HeapTupleClearHeapOnly(tuple) \
695  HeapTupleHeaderClearHeapOnly((tuple)->t_data)
696 
697 /* prototypes for functions in common/heaptuple.c */
698 extern Size heap_compute_data_size(TupleDesc tupleDesc,
699  const Datum *values, const bool *isnull);
700 extern void heap_fill_tuple(TupleDesc tupleDesc,
701  const Datum *values, const bool *isnull,
702  char *data, Size data_size,
703  uint16 *infomask, bits8 *bit);
704 extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);
705 extern Datum nocachegetattr(HeapTuple tup, int attnum,
706  TupleDesc tupleDesc);
707 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
708  bool *isnull);
709 extern Datum getmissingattr(TupleDesc tupleDesc,
710  int attnum, bool *isnull);
711 extern HeapTuple heap_copytuple(HeapTuple tuple);
713 extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);
714 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
715  const Datum *values, const bool *isnull);
717  TupleDesc tupleDesc,
718  const Datum *replValues,
719  const bool *replIsnull,
720  const bool *doReplace);
722  TupleDesc tupleDesc,
723  int nCols,
724  const int *replCols,
725  const Datum *replValues,
726  const bool *replIsnull);
727 extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
728  Datum *values, bool *isnull);
729 extern void heap_freetuple(HeapTuple htup);
730 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
731  const Datum *values, const bool *isnull);
732 extern void heap_free_minimal_tuple(MinimalTuple mtup);
736 extern size_t varsize_any(void *p);
737 extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
738 extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
739 
740 #ifndef FRONTEND
741 /*
742  * fastgetattr
743  * Fetch a user attribute's value as a Datum (might be either a
744  * value, or a pointer into the data area of the tuple).
745  *
746  * This must not be used when a system attribute might be requested.
747  * Furthermore, the passed attnum MUST be valid. Use heap_getattr()
748  * instead, if in doubt.
749  *
750  * This gets called many times, so we macro the cacheable and NULL
751  * lookups, and call nocachegetattr() for the rest.
752  */
753 static inline Datum
754 fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
755 {
756  Assert(attnum > 0);
757 
758  *isnull = false;
759  if (HeapTupleNoNulls(tup))
760  {
761  Form_pg_attribute att;
762 
763  att = TupleDescAttr(tupleDesc, attnum - 1);
764  if (att->attcacheoff >= 0)
765  return fetchatt(att, (char *) tup->t_data + tup->t_data->t_hoff +
766  att->attcacheoff);
767  else
768  return nocachegetattr(tup, attnum, tupleDesc);
769  }
770  else
771  {
772  if (att_isnull(attnum - 1, tup->t_data->t_bits))
773  {
774  *isnull = true;
775  return (Datum) NULL;
776  }
777  else
778  return nocachegetattr(tup, attnum, tupleDesc);
779  }
780 }
781 
782 /*
783  * heap_getattr
784  * Extract an attribute of a heap tuple and return it as a Datum.
785  * This works for either system or user attributes. The given attnum
786  * is properly range-checked.
787  *
788  * If the field in question has a NULL value, we return a zero Datum
789  * and set *isnull == true. Otherwise, we set *isnull == false.
790  *
791  * <tup> is the pointer to the heap tuple. <attnum> is the attribute
792  * number of the column (field) caller wants. <tupleDesc> is a
793  * pointer to the structure describing the row and all its fields.
794  *
795  */
796 static inline Datum
797 heap_getattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
798 {
799  if (attnum > 0)
800  {
801  if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))
802  return getmissingattr(tupleDesc, attnum, isnull);
803  else
804  return fastgetattr(tup, attnum, tupleDesc, isnull);
805  }
806  else
807  return heap_getsysattr(tup, attnum, tupleDesc, isnull);
808 }
809 #endif /* FRONTEND */
810 
811 #endif /* HTUP_DETAILS_H */
static Datum values[MAXATTR]
Definition: bootstrap.c:152
unsigned short uint16
Definition: c.h:492
unsigned int uint32
Definition: c.h:493
signed int int32
Definition: c.h:481
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:385
uint8 bits8
Definition: c.h:500
unsigned char uint8
Definition: c.h:491
uint32 CommandId
Definition: c.h:653
uint32 TransactionId
Definition: c.h:639
size_t Size
Definition: c.h:592
Size heap_compute_data_size(TupleDesc tupleDesc, const Datum *values, const bool *isnull)
Definition: heaptuple.c:215
static Datum heap_getattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: htup_details.h:792
struct HeapTupleFields HeapTupleFields
#define HeapTupleHeaderGetNatts(tup)
Definition: htup_details.h:529
HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, const Datum *replValues, const bool *replIsnull, const bool *doReplace)
Definition: heaptuple.c:1209
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:802
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:776
size_t varsize_any(void *p)
Definition: heaptuple.c:1594
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1576
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:723
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, const Datum *values, const bool *isnull)
Definition: heaptuple.c:1452
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, const int *replCols, const Datum *replValues, const bool *replIsnull)
Definition: heaptuple.c:1277
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, const Datum *values, const bool *isnull)
Definition: heaptuple.c:1116
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1523
bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:455
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:519
#define HeapTupleNoNulls(tuple)
Definition: htup_details.h:662
Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull)
Definition: heaptuple.c:147
HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1065
void heap_fill_tuple(TupleDesc tupleDesc, const Datum *values, const bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit)
Definition: heaptuple.c:400
struct DatumTupleFields DatumTupleFields
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:1345
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1535
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:619
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1080
StaticAssertDecl(MaxOffsetNumber< SpecTokenOffsetNumber, "invalid speculative token constant")
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1554
MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1053
static Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: htup_details.h:749
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1434
#define SpecTokenOffsetNumber
Definition: itemptr.h:63
Assert(fmt[strlen(fmt) - 1] !='\n')
#define MaxOffsetNumber
Definition: off.h:28
int16 attnum
Definition: pg_attribute.h:74
FormData_pg_attribute * Form_pg_attribute
Definition: pg_attribute.h:209
const void * data
uintptr_t Datum
Definition: postgres.h:64
unsigned int Oid
Definition: postgres_ext.h:31
HeapTupleHeader t_data
Definition: htup.h:68
TransactionId t_xmin
Definition: htup_details.h:124
union HeapTupleFields::@44 t_field3
CommandId t_cid
Definition: htup_details.h:129
TransactionId t_xmax
Definition: htup_details.h:125
TransactionId t_xvac
Definition: htup_details.h:130
union HeapTupleHeaderData::@45 t_choice
ItemPointerData t_ctid
Definition: htup_details.h:161
bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]
Definition: htup_details.h:178
HeapTupleFields t_heap
Definition: htup_details.h:157
DatumTupleFields t_datum
Definition: htup_details.h:158
char mt_padding[MINIMAL_TUPLE_PADDING]
Definition: htup_details.h:628
bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]
Definition: htup_details.h:640
#define TupleDescAttr(tupdesc, i)
Definition: tupdesc.h:92
static bool att_isnull(int ATT, const bits8 *BITS)
Definition: tupmacs.h:26
#define fetchatt(A, T)
Definition: tupmacs.h:46
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:391