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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
122typedef 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
134typedef 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)
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)
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) \
399do { \
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) \
407do { \
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) \
425do { \
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) \
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 \
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
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.
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)
629struct MinimalTupleData
630{
631 uint32 t_len; /* actual length of minimal tuple */
635 /* Fields below here must match HeapTupleHeaderData! */
637 uint16 t_infomask2; /* number of attributes + various flags */
638
639 uint16 t_infomask; /* various flag bits, see below */
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)
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)
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 */
698extern Size heap_compute_data_size(TupleDesc tupleDesc,
699 const Datum *values, const bool *isnull);
700extern void heap_fill_tuple(TupleDesc tupleDesc,
701 const Datum *values, const bool *isnull,
702 char *data, Size data_size,
703 uint16 *infomask, bits8 *bit);
704extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);
705extern Datum nocachegetattr(HeapTuple tup, int attnum,
706 TupleDesc tupleDesc);
707extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
708 bool *isnull);
709extern Datum getmissingattr(TupleDesc tupleDesc,
710 int attnum, bool *isnull);
713extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);
714extern 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);
727extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
728 Datum *values, bool *isnull);
729extern void heap_freetuple(HeapTuple htup);
730extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
731 const Datum *values, const bool *isnull);
732extern void heap_free_minimal_tuple(MinimalTuple mtup);
736extern size_t varsize_any(void *p);
737extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
738extern 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.
750 * This gets called many times, so we macro the cacheable and NULL
751 * lookups, and call nocachegetattr() for the rest.
752 */
753static inline Datum
754fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
755{
756 Assert(attnum > 0);
757
758 *isnull = false;
759 if (HeapTupleNoNulls(tup))
760 {
761 CompactAttribute *att;
762
763 att = TupleDescCompactAttr(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 */
796static inline Datum
797heap_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:151
uint8_t uint8
Definition: c.h:483
#define Assert(condition)
Definition: c.h:812
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:417
uint8 bits8
Definition: c.h:492
int32_t int32
Definition: c.h:481
uint16_t uint16
Definition: c.h:484
uint32_t uint32
Definition: c.h:485
uint32 CommandId
Definition: c.h:620
uint32 TransactionId
Definition: c.h:606
size_t Size
Definition: c.h:559
Size heap_compute_data_size(TupleDesc tupleDesc, const Datum *values, const bool *isnull)
Definition: heaptuple.c:219
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:1210
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:804
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:778
size_t varsize_any(void *p)
Definition: heaptuple.c:1595
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1577
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:725
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, const Datum *values, const bool *isnull)
Definition: heaptuple.c:1453
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, const int *replCols, const Datum *replValues, const bool *replIsnull)
Definition: heaptuple.c:1278
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, const Datum *values, const bool *isnull)
Definition: heaptuple.c:1117
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1524
bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:456
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:521
#define HeapTupleNoNulls(tuple)
Definition: htup_details.h:662
Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull)
Definition: heaptuple.c:151
HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1066
void heap_fill_tuple(TupleDesc tupleDesc, const Datum *values, const bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit)
Definition: heaptuple.c:401
struct DatumTupleFields DatumTupleFields
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:1346
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1536
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:619
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1081
StaticAssertDecl(MaxOffsetNumber< SpecTokenOffsetNumber, "invalid speculative token constant")
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1555
MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1054
static Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: htup_details.h:749
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1435
#define SpecTokenOffsetNumber
Definition: itemptr.h:63
#define MaxOffsetNumber
Definition: off.h:28
int16 attnum
Definition: pg_attribute.h:74
const void * data
uintptr_t Datum
Definition: postgres.h:64
unsigned int Oid
Definition: postgres_ext.h:31
int32 attcacheoff
Definition: tupdesc.h:68
HeapTupleHeader t_data
Definition: htup.h:68
union HeapTupleFields::@46 t_field3
TransactionId t_xmin
Definition: htup_details.h:124
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::@47 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
static CompactAttribute * TupleDescCompactAttr(TupleDesc tupdesc, int i)
Definition: tupdesc.h:169
static bool att_isnull(int ATT, const bits8 *BITS)
Definition: tupmacs.h:26
#define fetchatt(A, T)
Definition: tupmacs.h:47
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:391