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) 1996-2017, 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.
87  * Thus, a tuple is the latest version of its row iff XMAX is invalid or
88  * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
89  * either locked or deleted). One can follow the chain of t_ctid links
90  * to find the newest version of the row. Beware however that VACUUM might
91  * erase the pointed-to (newer) tuple before erasing the pointing (older)
92  * tuple. Hence, when following a t_ctid link, it is necessary to check
93  * to see if the referenced slot is empty or contains an unrelated tuple.
94  * Check that the referenced tuple has XMIN equal to the referencing tuple's
95  * XMAX to verify that it is actually the descendant version and not an
96  * unrelated tuple stored into a slot recently freed by VACUUM. If either
97  * check fails, one may assume that there is no live descendant version.
98  *
99  * t_ctid is sometimes used to store a speculative insertion token, instead
100  * of a real TID. A speculative token is set on a tuple that's being
101  * inserted, until the inserter is sure that it wants to go ahead with the
102  * insertion. Hence a token should only be seen on a tuple with an XMAX
103  * that's still in-progress, or invalid/aborted. The token is replaced with
104  * the tuple's real TID when the insertion is confirmed. One should never
105  * see a speculative insertion token while following a chain of t_ctid links,
106  * because they are not used on updates, only insertions.
107  *
108  * Following the fixed header fields, the nulls bitmap is stored (beginning
109  * at t_bits). The bitmap is *not* stored if t_infomask shows that there
110  * are no nulls in the tuple. If an OID field is present (as indicated by
111  * t_infomask), then it is stored just before the user data, which begins at
112  * the offset shown by t_hoff. Note that t_hoff must be a multiple of
113  * MAXALIGN.
114  */
115 
116 typedef struct HeapTupleFields
117 {
118  TransactionId t_xmin; /* inserting xact ID */
119  TransactionId t_xmax; /* deleting or locking xact ID */
120 
121  union
122  {
123  CommandId t_cid; /* inserting or deleting command ID, or both */
124  TransactionId t_xvac; /* old-style VACUUM FULL xact ID */
125  } t_field3;
127 
128 typedef struct DatumTupleFields
129 {
130  int32 datum_len_; /* varlena header (do not touch directly!) */
131 
132  int32 datum_typmod; /* -1, or identifier of a record type */
133 
134  Oid datum_typeid; /* composite type OID, or RECORDOID */
135 
136  /*
137  * datum_typeid cannot be a domain over composite, only plain composite,
138  * even if the datum is meant as a value of a domain-over-composite type.
139  * This is in line with the general principle that CoerceToDomain does not
140  * change the physical representation of the base type value.
141  *
142  * Note: field ordering is chosen with thought that Oid might someday
143  * widen to 64 bits.
144  */
146 
148 {
149  union
150  {
153  } t_choice;
154 
155  ItemPointerData t_ctid; /* current TID of this or newer tuple (or a
156  * speculative insertion token) */
157 
158  /* Fields below here must match MinimalTupleData! */
159 
160  uint16 t_infomask2; /* number of attributes + various flags */
161 
162  uint16 t_infomask; /* various flag bits, see below */
163 
164  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
165 
166  /* ^ - 23 bytes - ^ */
167 
168  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
169 
170  /* MORE DATA FOLLOWS AT END OF STRUCT */
171 };
172 
173 /* typedef appears in htup.h */
174 
175 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
176 
177 /*
178  * information stored in t_infomask:
179  */
180 #define HEAP_HASNULL 0x0001 /* has null attribute(s) */
181 #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
182 #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
183 #define HEAP_HASOID 0x0008 /* has an object-id field */
184 #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
185 #define HEAP_COMBOCID 0x0020 /* t_cid is a combo cid */
186 #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
187 #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
188 
189  /* xmax is a shared locker */
190 #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
191 
192 #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
193  HEAP_XMAX_KEYSHR_LOCK)
194 #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
195 #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
196 #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
197 #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
198 #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
199 #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
200 #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
201 #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
202  * VACUUM FULL; kept for binary
203  * upgrade support */
204 #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
205  * VACUUM FULL; kept for binary
206  * upgrade support */
207 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
208 
209 #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
210 
211 /*
212  * A tuple is only locked (i.e. not updated by its Xmax) if the
213  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
214  * not a multi and the EXCL_LOCK bit is set.
215  *
216  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
217  * aborted updater transaction.
218  *
219  * Beware of multiple evaluations of the argument.
220  */
221 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
222  (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
223  (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
224 
225 /*
226  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
227  * XMAX_EXCL_LOCK and XMAX_KEYSHR_LOCK must come from a tuple that was
228  * share-locked in 9.2 or earlier and then pg_upgrade'd.
229  *
230  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
231  * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a
232  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
233  * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and
234  * up, so if we see that combination we know for certain that the tuple was
235  * locked in an earlier release; since all such lockers are gone (they cannot
236  * survive through pg_upgrade), such tuples can safely be considered not
237  * locked.
238  *
239  * We must not resolve such multixacts locally, because the result would be
240  * bogus, regardless of where they stand with respect to the current valid
241  * multixact range.
242  */
243 #define HEAP_LOCKED_UPGRADED(infomask) \
244 ( \
245  ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
246  ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
247  (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
248 )
249 
250 /*
251  * Use these to test whether a particular lock is applied to a tuple
252  */
253 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
254  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
255 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
256  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
257 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
258  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
259 
260 /* turn these all off when Xmax is to change */
261 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
262  HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
263 
264 /*
265  * information stored in t_infomask2:
266  */
267 #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
268 /* bits 0x1800 are available */
269 #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
270  * modified, or tuple deleted */
271 #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
272 #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
273 
274 #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
275 
276 /*
277  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is
278  * only used in tuples that are in the hash table, and those don't need
279  * any visibility information, so we can overlay it on a visibility flag
280  * instead of using up a dedicated bit.
281  */
282 #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
283 
284 /*
285  * Special value used in t_ctid.ip_posid, to indicate that it holds a
286  * speculative insertion token rather than a real TID. This must be higher
287  * than MaxOffsetNumber, so that it can be distinguished from a valid
288  * offset number in a regular item pointer.
289  */
290 #define SpecTokenOffsetNumber 0xfffe
291 
292 /*
293  * HeapTupleHeader accessor macros
294  *
295  * Note: beware of multiple evaluations of "tup" argument. But the Set
296  * macros evaluate their other argument only once.
297  */
298 
299 /*
300  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
301  * originally used to insert the tuple. However, the tuple might actually
302  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
303  * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
304  * the xmin to FrozenTransactionId, and that value may still be encountered
305  * on disk.
306  */
307 #define HeapTupleHeaderGetRawXmin(tup) \
308 ( \
309  (tup)->t_choice.t_heap.t_xmin \
310 )
311 
312 #define HeapTupleHeaderGetXmin(tup) \
313 ( \
314  HeapTupleHeaderXminFrozen(tup) ? \
315  FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
316 )
317 
318 #define HeapTupleHeaderSetXmin(tup, xid) \
319 ( \
320  (tup)->t_choice.t_heap.t_xmin = (xid) \
321 )
322 
323 #define HeapTupleHeaderXminCommitted(tup) \
324 ( \
325  ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
326 )
327 
328 #define HeapTupleHeaderXminInvalid(tup) \
329 ( \
330  ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
331  HEAP_XMIN_INVALID \
332 )
333 
334 #define HeapTupleHeaderXminFrozen(tup) \
335 ( \
336  ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
337 )
338 
339 #define HeapTupleHeaderSetXminCommitted(tup) \
340 ( \
341  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
342  ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
343 )
344 
345 #define HeapTupleHeaderSetXminInvalid(tup) \
346 ( \
347  AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
348  ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
349 )
350 
351 #define HeapTupleHeaderSetXminFrozen(tup) \
352 ( \
353  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
354  ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
355 )
356 
357 /*
358  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid
359  * that updated a tuple, you might need to resolve the MultiXactId if certain
360  * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care
361  * to resolve the MultiXactId if necessary. This might involve multixact I/O,
362  * so it should only be used if absolutely necessary.
363  */
364 #define HeapTupleHeaderGetUpdateXid(tup) \
365 ( \
366  (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
367  ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
368  !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
369  HeapTupleGetUpdateXid(tup) \
370  : \
371  HeapTupleHeaderGetRawXmax(tup) \
372 )
373 
374 #define HeapTupleHeaderGetRawXmax(tup) \
375 ( \
376  (tup)->t_choice.t_heap.t_xmax \
377 )
378 
379 #define HeapTupleHeaderSetXmax(tup, xid) \
380 ( \
381  (tup)->t_choice.t_heap.t_xmax = (xid) \
382 )
383 
384 /*
385  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
386  * it is useful or not. Most code should use HeapTupleHeaderGetCmin or
387  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
388  * get a legitimate result, ie you are in the originating transaction!
389  */
390 #define HeapTupleHeaderGetRawCommandId(tup) \
391 ( \
392  (tup)->t_choice.t_heap.t_field3.t_cid \
393 )
394 
395 /* SetCmin is reasonably simple since we never need a combo CID */
396 #define HeapTupleHeaderSetCmin(tup, cid) \
397 do { \
398  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
399  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
400  (tup)->t_infomask &= ~HEAP_COMBOCID; \
401 } while (0)
402 
403 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
404 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
405 do { \
406  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
407  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
408  if (iscombo) \
409  (tup)->t_infomask |= HEAP_COMBOCID; \
410  else \
411  (tup)->t_infomask &= ~HEAP_COMBOCID; \
412 } while (0)
413 
414 #define HeapTupleHeaderGetXvac(tup) \
415 ( \
416  ((tup)->t_infomask & HEAP_MOVED) ? \
417  (tup)->t_choice.t_heap.t_field3.t_xvac \
418  : \
419  InvalidTransactionId \
420 )
421 
422 #define HeapTupleHeaderSetXvac(tup, xid) \
423 do { \
424  Assert((tup)->t_infomask & HEAP_MOVED); \
425  (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
426 } while (0)
427 
428 #define HeapTupleHeaderIsSpeculative(tup) \
429 ( \
430  (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \
431 )
432 
433 #define HeapTupleHeaderGetSpeculativeToken(tup) \
434 ( \
435  AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
436  ItemPointerGetBlockNumber(&(tup)->t_ctid) \
437 )
438 
439 #define HeapTupleHeaderSetSpeculativeToken(tup, token) \
440 ( \
441  ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
442 )
443 
444 #define HeapTupleHeaderGetDatumLength(tup) \
445  VARSIZE(tup)
446 
447 #define HeapTupleHeaderSetDatumLength(tup, len) \
448  SET_VARSIZE(tup, len)
449 
450 #define HeapTupleHeaderGetTypeId(tup) \
451 ( \
452  (tup)->t_choice.t_datum.datum_typeid \
453 )
454 
455 #define HeapTupleHeaderSetTypeId(tup, typeid) \
456 ( \
457  (tup)->t_choice.t_datum.datum_typeid = (typeid) \
458 )
459 
460 #define HeapTupleHeaderGetTypMod(tup) \
461 ( \
462  (tup)->t_choice.t_datum.datum_typmod \
463 )
464 
465 #define HeapTupleHeaderSetTypMod(tup, typmod) \
466 ( \
467  (tup)->t_choice.t_datum.datum_typmod = (typmod) \
468 )
469 
470 #define HeapTupleHeaderGetOid(tup) \
471 ( \
472  ((tup)->t_infomask & HEAP_HASOID) ? \
473  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
474  : \
475  InvalidOid \
476 )
477 
478 #define HeapTupleHeaderSetOid(tup, oid) \
479 do { \
480  Assert((tup)->t_infomask & HEAP_HASOID); \
481  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) = (oid); \
482 } while (0)
483 
484 /*
485  * Note that we stop considering a tuple HOT-updated as soon as it is known
486  * aborted or the would-be updating transaction is known aborted. For best
487  * efficiency, check tuple visibility before using this macro, so that the
488  * INVALID bits will be as up to date as possible.
489  */
490 #define HeapTupleHeaderIsHotUpdated(tup) \
491 ( \
492  ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
493  ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
494  !HeapTupleHeaderXminInvalid(tup) \
495 )
496 
497 #define HeapTupleHeaderSetHotUpdated(tup) \
498 ( \
499  (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
500 )
501 
502 #define HeapTupleHeaderClearHotUpdated(tup) \
503 ( \
504  (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
505 )
506 
507 #define HeapTupleHeaderIsHeapOnly(tup) \
508 ( \
509  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
510 )
511 
512 #define HeapTupleHeaderSetHeapOnly(tup) \
513 ( \
514  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
515 )
516 
517 #define HeapTupleHeaderClearHeapOnly(tup) \
518 ( \
519  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
520 )
521 
522 #define HeapTupleHeaderHasMatch(tup) \
523 ( \
524  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
525 )
526 
527 #define HeapTupleHeaderSetMatch(tup) \
528 ( \
529  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
530 )
531 
532 #define HeapTupleHeaderClearMatch(tup) \
533 ( \
534  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
535 )
536 
537 #define HeapTupleHeaderGetNatts(tup) \
538  ((tup)->t_infomask2 & HEAP_NATTS_MASK)
539 
540 #define HeapTupleHeaderSetNatts(tup, natts) \
541 ( \
542  (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
543 )
544 
545 #define HeapTupleHeaderHasExternal(tup) \
546  (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
547 
548 
549 /*
550  * BITMAPLEN(NATTS) -
551  * Computes size of null bitmap given number of data columns.
552  */
553 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
554 
555 /*
556  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
557  * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the
558  * other stuff that has to be on a disk page. Since heap pages use no
559  * "special space", there's no deduction for that.
560  *
561  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
562  * an otherwise-empty page can indeed hold a tuple of this size. Because
563  * ItemIds and tuples have different alignment requirements, don't assume that
564  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
565  */
566 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
567 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader)
568 
569 /*
570  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
571  * fit on one heap page. (Note that indexes could have more, because they
572  * use a smaller tuple header.) We arrive at the divisor because each tuple
573  * must be maxaligned, and it must have an associated item pointer.
574  *
575  * Note: with HOT, there could theoretically be more line pointers (not actual
576  * tuples) than this on a heap page. However we constrain the number of line
577  * pointers to this anyway, to avoid excessive line-pointer bloat and not
578  * require increases in the size of work arrays.
579  */
580 #define MaxHeapTuplesPerPage \
581  ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
582  (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
583 
584 /*
585  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
586  * data fields of char(n) and similar types. It need not have anything
587  * directly to do with the *actual* upper limit of varlena values, which
588  * is currently 1Gb (see TOAST structures in postgres.h). I've set it
589  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
590  */
591 #define MaxAttrSize (10 * 1024 * 1024)
592 
593 
594 /*
595  * MinimalTuple is an alternative representation that is used for transient
596  * tuples inside the executor, in places where transaction status information
597  * is not required, the tuple rowtype is known, and shaving off a few bytes
598  * is worthwhile because we need to store many tuples. The representation
599  * is chosen so that tuple access routines can work with either full or
600  * minimal tuples via a HeapTupleData pointer structure. The access routines
601  * see no difference, except that they must not access the transaction status
602  * or t_ctid fields because those aren't there.
603  *
604  * For the most part, MinimalTuples should be accessed via TupleTableSlot
605  * routines. These routines will prevent access to the "system columns"
606  * and thereby prevent accidental use of the nonexistent fields.
607  *
608  * MinimalTupleData contains a length word, some padding, and fields matching
609  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
610  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
611  * structs. This makes data alignment rules equivalent in both cases.
612  *
613  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
614  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
615  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
616  * data would start. This trick is what makes the structs seem equivalent.
617  *
618  * Note that t_hoff is computed the same as in a full tuple, hence it includes
619  * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
620  *
621  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
622  * other than the length word. tuplesort.c and tuplestore.c use this to avoid
623  * writing the padding to disk.
624  */
625 #define MINIMAL_TUPLE_OFFSET \
626  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
627 #define MINIMAL_TUPLE_PADDING \
628  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
629 #define MINIMAL_TUPLE_DATA_OFFSET \
630  offsetof(MinimalTupleData, t_infomask2)
631 
633 {
634  uint32 t_len; /* actual length of minimal tuple */
635 
636  char mt_padding[MINIMAL_TUPLE_PADDING];
637 
638  /* Fields below here must match HeapTupleHeaderData! */
639 
640  uint16 t_infomask2; /* number of attributes + various flags */
641 
642  uint16 t_infomask; /* various flag bits, see below */
643 
644  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
645 
646  /* ^ - 23 bytes - ^ */
647 
648  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
649 
650  /* MORE DATA FOLLOWS AT END OF STRUCT */
651 };
652 
653 /* typedef appears in htup.h */
654 
655 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
656 
657 
658 /*
659  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
660  */
661 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
662 
663 /*
664  * Accessor macros to be used with HeapTuple pointers.
665  */
666 
667 #define HeapTupleHasNulls(tuple) \
668  (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
669 
670 #define HeapTupleNoNulls(tuple) \
671  (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
672 
673 #define HeapTupleHasVarWidth(tuple) \
674  (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
675 
676 #define HeapTupleAllFixed(tuple) \
677  (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
678 
679 #define HeapTupleHasExternal(tuple) \
680  (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
681 
682 #define HeapTupleIsHotUpdated(tuple) \
683  HeapTupleHeaderIsHotUpdated((tuple)->t_data)
684 
685 #define HeapTupleSetHotUpdated(tuple) \
686  HeapTupleHeaderSetHotUpdated((tuple)->t_data)
687 
688 #define HeapTupleClearHotUpdated(tuple) \
689  HeapTupleHeaderClearHotUpdated((tuple)->t_data)
690 
691 #define HeapTupleIsHeapOnly(tuple) \
692  HeapTupleHeaderIsHeapOnly((tuple)->t_data)
693 
694 #define HeapTupleSetHeapOnly(tuple) \
695  HeapTupleHeaderSetHeapOnly((tuple)->t_data)
696 
697 #define HeapTupleClearHeapOnly(tuple) \
698  HeapTupleHeaderClearHeapOnly((tuple)->t_data)
699 
700 #define HeapTupleGetOid(tuple) \
701  HeapTupleHeaderGetOid((tuple)->t_data)
702 
703 #define HeapTupleSetOid(tuple, oid) \
704  HeapTupleHeaderSetOid((tuple)->t_data, (oid))
705 
706 
707 /* ----------------
708  * fastgetattr
709  *
710  * Fetch a user attribute's value as a Datum (might be either a
711  * value, or a pointer into the data area of the tuple).
712  *
713  * This must not be used when a system attribute might be requested.
714  * Furthermore, the passed attnum MUST be valid. Use heap_getattr()
715  * instead, if in doubt.
716  *
717  * This gets called many times, so we macro the cacheable and NULL
718  * lookups, and call nocachegetattr() for the rest.
719  * ----------------
720  */
721 
722 #if !defined(DISABLE_COMPLEX_MACRO)
723 
724 #define fastgetattr(tup, attnum, tupleDesc, isnull) \
725 ( \
726  AssertMacro((attnum) > 0), \
727  (*(isnull) = false), \
728  HeapTupleNoNulls(tup) ? \
729  ( \
730  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \
731  ( \
732  fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \
733  (char *) (tup)->t_data + (tup)->t_data->t_hoff + \
734  TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\
735  ) \
736  : \
737  nocachegetattr((tup), (attnum), (tupleDesc)) \
738  ) \
739  : \
740  ( \
741  att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \
742  ( \
743  (*(isnull) = true), \
744  (Datum)NULL \
745  ) \
746  : \
747  ( \
748  nocachegetattr((tup), (attnum), (tupleDesc)) \
749  ) \
750  ) \
751 )
752 #else /* defined(DISABLE_COMPLEX_MACRO) */
753 
754 extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
755  bool *isnull);
756 #endif /* defined(DISABLE_COMPLEX_MACRO) */
757 
758 
759 /* ----------------
760  * heap_getattr
761  *
762  * Extract an attribute of a heap tuple and return it as a Datum.
763  * This works for either system or user attributes. The given attnum
764  * is properly range-checked.
765  *
766  * If the field in question has a NULL value, we return a zero Datum
767  * and set *isnull == true. Otherwise, we set *isnull == false.
768  *
769  * <tup> is the pointer to the heap tuple. <attnum> is the attribute
770  * number of the column (field) caller wants. <tupleDesc> is a
771  * pointer to the structure describing the row and all its fields.
772  * ----------------
773  */
774 #define heap_getattr(tup, attnum, tupleDesc, isnull) \
775  ( \
776  ((attnum) > 0) ? \
777  ( \
778  ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
779  ( \
780  (*(isnull) = true), \
781  (Datum)NULL \
782  ) \
783  : \
784  fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \
785  ) \
786  : \
787  heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \
788  )
789 
790 
791 /* prototypes for functions in common/heaptuple.c */
793  Datum *values, bool *isnull);
795  Datum *values, bool *isnull,
796  char *data, Size data_size,
797  uint16 *infomask, bits8 *bit);
798 extern bool heap_attisnull(HeapTuple tup, int attnum);
799 extern Datum nocachegetattr(HeapTuple tup, int attnum,
800  TupleDesc att);
801 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
802  bool *isnull);
803 extern HeapTuple heap_copytuple(HeapTuple tuple);
806 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
807  Datum *values, bool *isnull);
810  Datum *replValues,
811  bool *replIsnull,
812  bool *doReplace);
815  int nCols,
816  int *replCols,
817  Datum *replValues,
818  bool *replIsnull);
820  Datum *values, bool *isnull);
821 extern void heap_freetuple(HeapTuple htup);
822 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
823  Datum *values, bool *isnull);
824 extern void heap_free_minimal_tuple(MinimalTuple mtup);
828 
829 #endif /* HTUP_DETAILS_H */
uint32 CommandId
Definition: c.h:459
#define fastgetattr(tup, attnum, tupleDesc, isnull)
Definition: htup_details.h:724
HeapTupleFields t_heap
Definition: htup_details.h:151
bool heap_attisnull(HeapTuple tup, int attnum)
Definition: heaptuple.c:296
uint32 TransactionId
Definition: c.h:445
Size heap_compute_data_size(TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:85
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1373
unsigned char uint8
Definition: c.h:294
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1499
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:637
struct DatumTupleFields DatumTupleFields
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:555
unsigned int Oid
Definition: postgres_ext.h:31
DatumTupleFields t_datum
Definition: htup_details.h:152
signed int int32
Definition: c.h:284
TransactionId t_xmax
Definition: htup_details.h:119
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1468
unsigned short uint16
Definition: c.h:295
HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *replValues, bool *replIsnull, bool *doReplace)
Definition: heaptuple.c:794
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1521
ItemPointerData t_ctid
Definition: htup_details.h:155
unsigned int uint32
Definition: c.h:296
TransactionId t_xmin
Definition: htup_details.h:118
union HeapTupleFields::@44 t_field3
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:627
uint8 bits8
Definition: c.h:303
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1391
struct HeapTupleFields HeapTupleFields
uintptr_t Datum
Definition: postgres.h:372
TransactionId t_xvac
Definition: htup_details.h:124
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:936
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:695
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1480
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:611
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull)
Definition: heaptuple.c:865
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:361
size_t Size
Definition: c.h:404
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att)
Definition: heaptuple.c:351
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:145
CommandId t_cid
Definition: htup_details.h:123
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:659