PostgreSQL Source Code  git master
htup_details.h
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * htup_details.h
4  * POSTGRES heap tuple header definitions.
5  *
6  *
7  * Portions Copyright (c) 1996-2018, 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/tupdesc.h"
19 #include "access/tupmacs.h"
20 #include "access/transam.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 is set in t_infomask)
69  * user data fields
70  *
71  * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three
72  * physical fields. Xmin and Xmax are always really stored, but Cmin, Cmax
73  * and Xvac share a field. This works because we know that Cmin and Cmax
74  * are only interesting for the lifetime of the inserting and deleting
75  * transaction respectively. If a tuple is inserted and deleted in the same
76  * transaction, we store a "combo" command id that can be mapped to the real
77  * cmin and cmax, but only by use of local state within the originating
78  * backend. See combocid.c for more details. Meanwhile, Xvac is only set by
79  * old-style VACUUM FULL, which does not have any command sub-structure and so
80  * does not need either Cmin or Cmax. (This requires that old-style VACUUM
81  * FULL never try to move a tuple whose Cmin or Cmax is still interesting,
82  * ie, an insert-in-progress or delete-in-progress tuple.)
83  *
84  * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
85  * is initialized with its own TID (location). If the tuple is ever updated,
86  * its t_ctid is changed to point to the replacement version of the tuple or
87  * the block number (ip_blkid) is invalidated if the tuple is moved from one
88  * partition to another partition relation due to an update of the partition
89  * key. Thus, a tuple is the latest version of its row iff XMAX is invalid or
90  * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
91  * either locked or deleted). One can follow the chain of t_ctid links
92  * to find the newest version of the row. Beware however that VACUUM might
93  * erase the pointed-to (newer) tuple before erasing the pointing (older)
94  * tuple. Hence, when following a t_ctid link, it is necessary to check
95  * to see if the referenced slot is empty or contains an unrelated tuple.
96  * Check that the referenced tuple has XMIN equal to the referencing tuple's
97  * XMAX to verify that it is actually the descendant version and not an
98  * unrelated tuple stored into a slot recently freed by VACUUM. If either
99  * check fails, one may assume that there is no live descendant version.
100  *
101  * t_ctid is sometimes used to store a speculative insertion token, instead
102  * of a real TID. A speculative token is set on a tuple that's being
103  * inserted, until the inserter is sure that it wants to go ahead with the
104  * insertion. Hence a token should only be seen on a tuple with an XMAX
105  * that's still in-progress, or invalid/aborted. The token is replaced with
106  * the tuple's real TID when the insertion is confirmed. One should never
107  * see a speculative insertion token while following a chain of t_ctid links,
108  * because they are not used on updates, only insertions.
109  *
110  * Following the fixed header fields, the nulls bitmap is stored (beginning
111  * at t_bits). The bitmap is *not* stored if t_infomask shows that there
112  * are no nulls in the tuple. If an OID field is present (as indicated by
113  * t_infomask), then it is stored just before the user data, which begins at
114  * the offset shown by t_hoff. Note that t_hoff must be a multiple of
115  * MAXALIGN.
116  */
117 
118 typedef struct HeapTupleFields
119 {
120  TransactionId t_xmin; /* inserting xact ID */
121  TransactionId t_xmax; /* deleting or locking xact ID */
122 
123  union
124  {
125  CommandId t_cid; /* inserting or deleting command ID, or both */
126  TransactionId t_xvac; /* old-style VACUUM FULL xact ID */
127  } t_field3;
129 
130 typedef struct DatumTupleFields
131 {
132  int32 datum_len_; /* varlena header (do not touch directly!) */
133 
134  int32 datum_typmod; /* -1, or identifier of a record type */
135 
136  Oid datum_typeid; /* composite type OID, or RECORDOID */
137 
138  /*
139  * datum_typeid cannot be a domain over composite, only plain composite,
140  * even if the datum is meant as a value of a domain-over-composite type.
141  * This is in line with the general principle that CoerceToDomain does not
142  * change the physical representation of the base type value.
143  *
144  * Note: field ordering is chosen with thought that Oid might someday
145  * widen to 64 bits.
146  */
148 
150 {
151  union
152  {
155  } t_choice;
156 
157  ItemPointerData t_ctid; /* current TID of this or newer tuple (or a
158  * speculative insertion token) */
159 
160  /* Fields below here must match MinimalTupleData! */
161 
162 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2
163  uint16 t_infomask2; /* number of attributes + various flags */
164 
165 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3
166  uint16 t_infomask; /* various flag bits, see below */
167 
168 #define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4
169  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
170 
171  /* ^ - 23 bytes - ^ */
172 
173 #define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5
174  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
175 
176  /* MORE DATA FOLLOWS AT END OF STRUCT */
177 };
178 
179 /* typedef appears in htup.h */
180 
181 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
182 
183 /*
184  * information stored in t_infomask:
185  */
186 #define HEAP_HASNULL 0x0001 /* has null attribute(s) */
187 #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
188 #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
189 #define HEAP_HASOID 0x0008 /* has an object-id field */
190 #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
191 #define HEAP_COMBOCID 0x0020 /* t_cid is a combo cid */
192 #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
193 #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
194 
195  /* xmax is a shared locker */
196 #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
197 
198 #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
199  HEAP_XMAX_KEYSHR_LOCK)
200 #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
201 #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
202 #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
203 #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
204 #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
205 #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
206 #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
207 #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
208  * VACUUM FULL; kept for binary
209  * upgrade support */
210 #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
211  * VACUUM FULL; kept for binary
212  * upgrade support */
213 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
214 
215 #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
216 
217 /*
218  * A tuple is only locked (i.e. not updated by its Xmax) if the
219  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
220  * not a multi and the EXCL_LOCK bit is set.
221  *
222  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
223  * aborted updater transaction.
224  *
225  * Beware of multiple evaluations of the argument.
226  */
227 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
228  (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
229  (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
230 
231 /*
232  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
233  * XMAX_EXCL_LOCK and XMAX_KEYSHR_LOCK must come from a tuple that was
234  * share-locked in 9.2 or earlier and then pg_upgrade'd.
235  *
236  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
237  * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a
238  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
239  * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and
240  * up, so if we see that combination we know for certain that the tuple was
241  * locked in an earlier release; since all such lockers are gone (they cannot
242  * survive through pg_upgrade), such tuples can safely be considered not
243  * locked.
244  *
245  * We must not resolve such multixacts locally, because the result would be
246  * bogus, regardless of where they stand with respect to the current valid
247  * multixact range.
248  */
249 #define HEAP_LOCKED_UPGRADED(infomask) \
250 ( \
251  ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
252  ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
253  (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
254 )
255 
256 /*
257  * Use these to test whether a particular lock is applied to a tuple
258  */
259 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
260  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
261 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
262  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
263 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
264  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
265 
266 /* turn these all off when Xmax is to change */
267 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
268  HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
269 
270 /*
271  * information stored in t_infomask2:
272  */
273 #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
274 /* bits 0x1800 are available */
275 #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
276  * modified, or tuple deleted */
277 #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
278 #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
279 
280 #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
281 
282 /*
283  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is
284  * only used in tuples that are in the hash table, and those don't need
285  * any visibility information, so we can overlay it on a visibility flag
286  * instead of using up a dedicated bit.
287  */
288 #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
289 
290 /*
291  * Special value used in t_ctid.ip_posid, to indicate that it holds a
292  * speculative insertion token rather than a real TID. This must be higher
293  * than MaxOffsetNumber, so that it can be distinguished from a valid
294  * offset number in a regular item pointer.
295  */
296 #define SpecTokenOffsetNumber 0xfffe
297 
298 /*
299  * HeapTupleHeader accessor macros
300  *
301  * Note: beware of multiple evaluations of "tup" argument. But the Set
302  * macros evaluate their other argument only once.
303  */
304 
305 /*
306  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
307  * originally used to insert the tuple. However, the tuple might actually
308  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
309  * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
310  * the xmin to FrozenTransactionId, and that value may still be encountered
311  * on disk.
312  */
313 #define HeapTupleHeaderGetRawXmin(tup) \
314 ( \
315  (tup)->t_choice.t_heap.t_xmin \
316 )
317 
318 #define HeapTupleHeaderGetXmin(tup) \
319 ( \
320  HeapTupleHeaderXminFrozen(tup) ? \
321  FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
322 )
323 
324 #define HeapTupleHeaderSetXmin(tup, xid) \
325 ( \
326  (tup)->t_choice.t_heap.t_xmin = (xid) \
327 )
328 
329 #define HeapTupleHeaderXminCommitted(tup) \
330 ( \
331  ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
332 )
333 
334 #define HeapTupleHeaderXminInvalid(tup) \
335 ( \
336  ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
337  HEAP_XMIN_INVALID \
338 )
339 
340 #define HeapTupleHeaderXminFrozen(tup) \
341 ( \
342  ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
343 )
344 
345 #define HeapTupleHeaderSetXminCommitted(tup) \
346 ( \
347  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
348  ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
349 )
350 
351 #define HeapTupleHeaderSetXminInvalid(tup) \
352 ( \
353  AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
354  ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
355 )
356 
357 #define HeapTupleHeaderSetXminFrozen(tup) \
358 ( \
359  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
360  ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
361 )
362 
363 /*
364  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid
365  * that updated a tuple, you might need to resolve the MultiXactId if certain
366  * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care
367  * to resolve the MultiXactId if necessary. This might involve multixact I/O,
368  * so it should only be used if absolutely necessary.
369  */
370 #define HeapTupleHeaderGetUpdateXid(tup) \
371 ( \
372  (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
373  ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
374  !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
375  HeapTupleGetUpdateXid(tup) \
376  : \
377  HeapTupleHeaderGetRawXmax(tup) \
378 )
379 
380 #define HeapTupleHeaderGetRawXmax(tup) \
381 ( \
382  (tup)->t_choice.t_heap.t_xmax \
383 )
384 
385 #define HeapTupleHeaderSetXmax(tup, xid) \
386 ( \
387  (tup)->t_choice.t_heap.t_xmax = (xid) \
388 )
389 
390 /*
391  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
392  * it is useful or not. Most code should use HeapTupleHeaderGetCmin or
393  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
394  * get a legitimate result, ie you are in the originating transaction!
395  */
396 #define HeapTupleHeaderGetRawCommandId(tup) \
397 ( \
398  (tup)->t_choice.t_heap.t_field3.t_cid \
399 )
400 
401 /* SetCmin is reasonably simple since we never need a combo CID */
402 #define HeapTupleHeaderSetCmin(tup, cid) \
403 do { \
404  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
405  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
406  (tup)->t_infomask &= ~HEAP_COMBOCID; \
407 } while (0)
408 
409 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
410 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
411 do { \
412  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
413  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
414  if (iscombo) \
415  (tup)->t_infomask |= HEAP_COMBOCID; \
416  else \
417  (tup)->t_infomask &= ~HEAP_COMBOCID; \
418 } while (0)
419 
420 #define HeapTupleHeaderGetXvac(tup) \
421 ( \
422  ((tup)->t_infomask & HEAP_MOVED) ? \
423  (tup)->t_choice.t_heap.t_field3.t_xvac \
424  : \
425  InvalidTransactionId \
426 )
427 
428 #define HeapTupleHeaderSetXvac(tup, xid) \
429 do { \
430  Assert((tup)->t_infomask & HEAP_MOVED); \
431  (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
432 } while (0)
433 
434 #define HeapTupleHeaderIsSpeculative(tup) \
435 ( \
436  (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \
437 )
438 
439 #define HeapTupleHeaderGetSpeculativeToken(tup) \
440 ( \
441  AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
442  ItemPointerGetBlockNumber(&(tup)->t_ctid) \
443 )
444 
445 #define HeapTupleHeaderSetSpeculativeToken(tup, token) \
446 ( \
447  ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
448 )
449 
450 #define HeapTupleHeaderSetMovedPartitions(tup) \
451  ItemPointerSetMovedPartitions(&(tup)->t_ctid)
452 
453 #define HeapTupleHeaderIndicatesMovedPartitions(tup) \
454  ItemPointerIndicatesMovedPartitions(&tup->t_ctid)
455 
456 #define HeapTupleHeaderGetDatumLength(tup) \
457  VARSIZE(tup)
458 
459 #define HeapTupleHeaderSetDatumLength(tup, len) \
460  SET_VARSIZE(tup, len)
461 
462 #define HeapTupleHeaderGetTypeId(tup) \
463 ( \
464  (tup)->t_choice.t_datum.datum_typeid \
465 )
466 
467 #define HeapTupleHeaderSetTypeId(tup, typeid) \
468 ( \
469  (tup)->t_choice.t_datum.datum_typeid = (typeid) \
470 )
471 
472 #define HeapTupleHeaderGetTypMod(tup) \
473 ( \
474  (tup)->t_choice.t_datum.datum_typmod \
475 )
476 
477 #define HeapTupleHeaderSetTypMod(tup, typmod) \
478 ( \
479  (tup)->t_choice.t_datum.datum_typmod = (typmod) \
480 )
481 
482 #define HeapTupleHeaderGetOid(tup) \
483 ( \
484  ((tup)->t_infomask & HEAP_HASOID) ? \
485  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
486  : \
487  InvalidOid \
488 )
489 
490 #define HeapTupleHeaderSetOid(tup, oid) \
491 do { \
492  Assert((tup)->t_infomask & HEAP_HASOID); \
493  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) = (oid); \
494 } while (0)
495 
496 /*
497  * Note that we stop considering a tuple HOT-updated as soon as it is known
498  * aborted or the would-be updating transaction is known aborted. For best
499  * efficiency, check tuple visibility before using this macro, so that the
500  * INVALID bits will be as up to date as possible.
501  */
502 #define HeapTupleHeaderIsHotUpdated(tup) \
503 ( \
504  ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
505  ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
506  !HeapTupleHeaderXminInvalid(tup) \
507 )
508 
509 #define HeapTupleHeaderSetHotUpdated(tup) \
510 ( \
511  (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
512 )
513 
514 #define HeapTupleHeaderClearHotUpdated(tup) \
515 ( \
516  (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
517 )
518 
519 #define HeapTupleHeaderIsHeapOnly(tup) \
520 ( \
521  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
522 )
523 
524 #define HeapTupleHeaderSetHeapOnly(tup) \
525 ( \
526  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
527 )
528 
529 #define HeapTupleHeaderClearHeapOnly(tup) \
530 ( \
531  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
532 )
533 
534 #define HeapTupleHeaderHasMatch(tup) \
535 ( \
536  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
537 )
538 
539 #define HeapTupleHeaderSetMatch(tup) \
540 ( \
541  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
542 )
543 
544 #define HeapTupleHeaderClearMatch(tup) \
545 ( \
546  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
547 )
548 
549 #define HeapTupleHeaderGetNatts(tup) \
550  ((tup)->t_infomask2 & HEAP_NATTS_MASK)
551 
552 #define HeapTupleHeaderSetNatts(tup, natts) \
553 ( \
554  (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
555 )
556 
557 #define HeapTupleHeaderHasExternal(tup) \
558  (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
559 
560 
561 /*
562  * BITMAPLEN(NATTS) -
563  * Computes size of null bitmap given number of data columns.
564  */
565 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
566 
567 /*
568  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
569  * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the
570  * other stuff that has to be on a disk page. Since heap pages use no
571  * "special space", there's no deduction for that.
572  *
573  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
574  * an otherwise-empty page can indeed hold a tuple of this size. Because
575  * ItemIds and tuples have different alignment requirements, don't assume that
576  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
577  */
578 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
579 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader)
580 
581 /*
582  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
583  * fit on one heap page. (Note that indexes could have more, because they
584  * use a smaller tuple header.) We arrive at the divisor because each tuple
585  * must be maxaligned, and it must have an associated item pointer.
586  *
587  * Note: with HOT, there could theoretically be more line pointers (not actual
588  * tuples) than this on a heap page. However we constrain the number of line
589  * pointers to this anyway, to avoid excessive line-pointer bloat and not
590  * require increases in the size of work arrays.
591  */
592 #define MaxHeapTuplesPerPage \
593  ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
594  (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
595 
596 /*
597  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
598  * data fields of char(n) and similar types. It need not have anything
599  * directly to do with the *actual* upper limit of varlena values, which
600  * is currently 1Gb (see TOAST structures in postgres.h). I've set it
601  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
602  */
603 #define MaxAttrSize (10 * 1024 * 1024)
604 
605 
606 /*
607  * MinimalTuple is an alternative representation that is used for transient
608  * tuples inside the executor, in places where transaction status information
609  * is not required, the tuple rowtype is known, and shaving off a few bytes
610  * is worthwhile because we need to store many tuples. The representation
611  * is chosen so that tuple access routines can work with either full or
612  * minimal tuples via a HeapTupleData pointer structure. The access routines
613  * see no difference, except that they must not access the transaction status
614  * or t_ctid fields because those aren't there.
615  *
616  * For the most part, MinimalTuples should be accessed via TupleTableSlot
617  * routines. These routines will prevent access to the "system columns"
618  * and thereby prevent accidental use of the nonexistent fields.
619  *
620  * MinimalTupleData contains a length word, some padding, and fields matching
621  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
622  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
623  * structs. This makes data alignment rules equivalent in both cases.
624  *
625  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
626  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
627  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
628  * data would start. This trick is what makes the structs seem equivalent.
629  *
630  * Note that t_hoff is computed the same as in a full tuple, hence it includes
631  * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
632  *
633  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
634  * other than the length word. tuplesort.c and tuplestore.c use this to avoid
635  * writing the padding to disk.
636  */
637 #define MINIMAL_TUPLE_OFFSET \
638  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
639 #define MINIMAL_TUPLE_PADDING \
640  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
641 #define MINIMAL_TUPLE_DATA_OFFSET \
642  offsetof(MinimalTupleData, t_infomask2)
643 
645 {
646  uint32 t_len; /* actual length of minimal tuple */
647 
648  char mt_padding[MINIMAL_TUPLE_PADDING];
649 
650  /* Fields below here must match HeapTupleHeaderData! */
651 
652  uint16 t_infomask2; /* number of attributes + various flags */
653 
654  uint16 t_infomask; /* various flag bits, see below */
655 
656  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
657 
658  /* ^ - 23 bytes - ^ */
659 
660  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
661 
662  /* MORE DATA FOLLOWS AT END OF STRUCT */
663 };
664 
665 /* typedef appears in htup.h */
666 
667 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
668 
669 
670 /*
671  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
672  */
673 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
674 
675 /*
676  * Accessor macros to be used with HeapTuple pointers.
677  */
678 
679 #define HeapTupleHasNulls(tuple) \
680  (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
681 
682 #define HeapTupleNoNulls(tuple) \
683  (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
684 
685 #define HeapTupleHasVarWidth(tuple) \
686  (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
687 
688 #define HeapTupleAllFixed(tuple) \
689  (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
690 
691 #define HeapTupleHasExternal(tuple) \
692  (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
693 
694 #define HeapTupleIsHotUpdated(tuple) \
695  HeapTupleHeaderIsHotUpdated((tuple)->t_data)
696 
697 #define HeapTupleSetHotUpdated(tuple) \
698  HeapTupleHeaderSetHotUpdated((tuple)->t_data)
699 
700 #define HeapTupleClearHotUpdated(tuple) \
701  HeapTupleHeaderClearHotUpdated((tuple)->t_data)
702 
703 #define HeapTupleIsHeapOnly(tuple) \
704  HeapTupleHeaderIsHeapOnly((tuple)->t_data)
705 
706 #define HeapTupleSetHeapOnly(tuple) \
707  HeapTupleHeaderSetHeapOnly((tuple)->t_data)
708 
709 #define HeapTupleClearHeapOnly(tuple) \
710  HeapTupleHeaderClearHeapOnly((tuple)->t_data)
711 
712 #define HeapTupleGetOid(tuple) \
713  HeapTupleHeaderGetOid((tuple)->t_data)
714 
715 #define HeapTupleSetOid(tuple, oid) \
716  HeapTupleHeaderSetOid((tuple)->t_data, (oid))
717 
718 
719 /* ----------------
720  * fastgetattr
721  *
722  * Fetch a user attribute's value as a Datum (might be either a
723  * value, or a pointer into the data area of the tuple).
724  *
725  * This must not be used when a system attribute might be requested.
726  * Furthermore, the passed attnum MUST be valid. Use heap_getattr()
727  * instead, if in doubt.
728  *
729  * This gets called many times, so we macro the cacheable and NULL
730  * lookups, and call nocachegetattr() for the rest.
731  * ----------------
732  */
733 
734 #if !defined(DISABLE_COMPLEX_MACRO)
735 
736 #define fastgetattr(tup, attnum, tupleDesc, isnull) \
737 ( \
738  AssertMacro((attnum) > 0), \
739  (*(isnull) = false), \
740  HeapTupleNoNulls(tup) ? \
741  ( \
742  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \
743  ( \
744  fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \
745  (char *) (tup)->t_data + (tup)->t_data->t_hoff + \
746  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\
747  ) \
748  : \
749  nocachegetattr((tup), (attnum), (tupleDesc)) \
750  ) \
751  : \
752  ( \
753  att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \
754  ( \
755  (*(isnull) = true), \
756  (Datum)NULL \
757  ) \
758  : \
759  ( \
760  nocachegetattr((tup), (attnum), (tupleDesc)) \
761  ) \
762  ) \
763 )
764 #else /* defined(DISABLE_COMPLEX_MACRO) */
765 
767  bool *isnull);
768 #endif /* defined(DISABLE_COMPLEX_MACRO) */
769 
770 
771 /* ----------------
772  * heap_getattr
773  *
774  * Extract an attribute of a heap tuple and return it as a Datum.
775  * This works for either system or user attributes. The given attnum
776  * is properly range-checked.
777  *
778  * If the field in question has a NULL value, we return a zero Datum
779  * and set *isnull == true. Otherwise, we set *isnull == false.
780  *
781  * <tup> is the pointer to the heap tuple. <attnum> is the attribute
782  * number of the column (field) caller wants. <tupleDesc> is a
783  * pointer to the structure describing the row and all its fields.
784  * ----------------
785  */
786 #define heap_getattr(tup, attnum, tupleDesc, isnull) \
787  ( \
788  ((attnum) > 0) ? \
789  ( \
790  ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
791  ( \
792  (*(isnull) = true), \
793  (Datum)NULL \
794  ) \
795  : \
796  fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \
797  ) \
798  : \
799  heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \
800  )
801 
802 
803 /* prototypes for functions in common/heaptuple.c */
805  Datum *values, bool *isnull);
807  Datum *values, bool *isnull,
808  char *data, Size data_size,
809  uint16 *infomask, bits8 *bit);
810 extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);
811 extern Datum nocachegetattr(HeapTuple tup, int attnum,
812  TupleDesc att);
814  bool *isnull);
815 extern HeapTuple heap_copytuple(HeapTuple tuple);
818 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
819  Datum *values, bool *isnull);
822  Datum *replValues,
823  bool *replIsnull,
824  bool *doReplace);
827  int nCols,
828  int *replCols,
829  Datum *replValues,
830  bool *replIsnull);
832  Datum *values, bool *isnull);
833 extern void heap_freetuple(HeapTuple htup);
834 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
835  Datum *values, bool *isnull);
836 extern void heap_free_minimal_tuple(MinimalTuple mtup);
840 extern size_t varsize_any(void *p);
843 
844 #endif /* HTUP_DETAILS_H */
uint32 CommandId
Definition: c.h:488
#define fastgetattr(tup, attnum, tupleDesc, isnull)
Definition: htup_details.h:736
HeapTupleFields t_heap
Definition: htup_details.h:153
uint32 TransactionId
Definition: c.h:474
Size heap_compute_data_size(TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:157
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1773
unsigned char uint8
Definition: c.h:323
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1899
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:748
struct DatumTupleFields DatumTupleFields
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:666
size_t varsize_any(void *p)
Definition: heaptuple.c:1939
unsigned int Oid
Definition: postgres_ext.h:31
DatumTupleFields t_datum
Definition: htup_details.h:154
signed int int32
Definition: c.h:313
TransactionId t_xmax
Definition: htup_details.h:121
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1868
unsigned short uint16
Definition: c.h:324
HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *replValues, bool *replIsnull, bool *doReplace)
Definition: heaptuple.c:1173
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1921
ItemPointerData t_ctid
Definition: htup_details.h:157
unsigned int uint32
Definition: c.h:325
TransactionId t_xmin
Definition: htup_details.h:120
union HeapTupleFields::@44 t_field3
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:639
uint8 bits8
Definition: c.h:332
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1791
struct HeapTupleFields HeapTupleFields
bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
Definition: heaptuple.c:397
uintptr_t Datum
Definition: postgres.h:365
TransactionId t_xvac
Definition: htup_details.h:126
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:1315
int16 attnum
Definition: pg_attribute.h:79
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1074
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1880
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:722
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull)
Definition: heaptuple.c:1244
MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1011
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:362
size_t Size
Definition: c.h:433
HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1023
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att)
Definition: heaptuple.c:462
static Datum values[MAXATTR]
Definition: bootstrap.c:164
void heap_fill_tuple(TupleDesc tupleDesc, Datum *values, bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit)
Definition: heaptuple.c:342
CommandId t_cid
Definition: htup_details.h:125
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:1038