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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) 1996-2017, 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  * Note: field ordering is chosen with thought that Oid might someday
138  * widen to 64 bits.
139  */
141 
143 {
144  union
145  {
148  } t_choice;
149 
150  ItemPointerData t_ctid; /* current TID of this or newer tuple (or a
151  * speculative insertion token) */
152 
153  /* Fields below here must match MinimalTupleData! */
154 
155  uint16 t_infomask2; /* number of attributes + various flags */
156 
157  uint16 t_infomask; /* various flag bits, see below */
158 
159  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
160 
161  /* ^ - 23 bytes - ^ */
162 
163  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
164 
165  /* MORE DATA FOLLOWS AT END OF STRUCT */
166 };
167 
168 /* typedef appears in tupbasics.h */
169 
170 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
171 
172 /*
173  * information stored in t_infomask:
174  */
175 #define HEAP_HASNULL 0x0001 /* has null attribute(s) */
176 #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
177 #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
178 #define HEAP_HASOID 0x0008 /* has an object-id field */
179 #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
180 #define HEAP_COMBOCID 0x0020 /* t_cid is a combo cid */
181 #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
182 #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
183 
184  /* xmax is a shared locker */
185 #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
186 
187 #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
188  HEAP_XMAX_KEYSHR_LOCK)
189 #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
190 #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
191 #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
192 #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
193 #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
194 #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
195 #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
196 #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
197  * VACUUM FULL; kept for binary
198  * upgrade support */
199 #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
200  * VACUUM FULL; kept for binary
201  * upgrade support */
202 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
203 
204 #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
205 
206 /*
207  * A tuple is only locked (i.e. not updated by its Xmax) if the
208  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
209  * not a multi and the EXCL_LOCK bit is set.
210  *
211  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
212  * aborted updater transaction.
213  *
214  * Beware of multiple evaluations of the argument.
215  */
216 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
217  (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
218  (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
219 
220 /*
221  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
222  * XMAX_EXCL_LOCK and XMAX_KEYSHR_LOCK must come from a tuple that was
223  * share-locked in 9.2 or earlier and then pg_upgrade'd.
224  *
225  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
226  * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a
227  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
228  * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and
229  * up, so if we see that combination we know for certain that the tuple was
230  * locked in an earlier release; since all such lockers are gone (they cannot
231  * survive through pg_upgrade), such tuples can safely be considered not
232  * locked.
233  *
234  * We must not resolve such multixacts locally, because the result would be
235  * bogus, regardless of where they stand with respect to the current valid
236  * multixact range.
237  */
238 #define HEAP_LOCKED_UPGRADED(infomask) \
239 ( \
240  ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
241  ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
242  (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
243 )
244 
245 /*
246  * Use these to test whether a particular lock is applied to a tuple
247  */
248 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
249  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
250 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
251  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
252 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
253  (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
254 
255 /* turn these all off when Xmax is to change */
256 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
257  HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
258 
259 /*
260  * information stored in t_infomask2:
261  */
262 #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
263 /* bits 0x1800 are available */
264 #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
265  * modified, or tuple deleted */
266 #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
267 #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
268 
269 #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
270 
271 /*
272  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is
273  * only used in tuples that are in the hash table, and those don't need
274  * any visibility information, so we can overlay it on a visibility flag
275  * instead of using up a dedicated bit.
276  */
277 #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
278 
279 /*
280  * Special value used in t_ctid.ip_posid, to indicate that it holds a
281  * speculative insertion token rather than a real TID. This must be higher
282  * than MaxOffsetNumber, so that it can be distinguished from a valid
283  * offset number in a regular item pointer.
284  */
285 #define SpecTokenOffsetNumber 0xfffe
286 
287 /*
288  * HeapTupleHeader accessor macros
289  *
290  * Note: beware of multiple evaluations of "tup" argument. But the Set
291  * macros evaluate their other argument only once.
292  */
293 
294 /*
295  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
296  * originally used to insert the tuple. However, the tuple might actually
297  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
298  * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
299  * the xmin to FrozenTransactionId, and that value may still be encountered
300  * on disk.
301  */
302 #define HeapTupleHeaderGetRawXmin(tup) \
303 ( \
304  (tup)->t_choice.t_heap.t_xmin \
305 )
306 
307 #define HeapTupleHeaderGetXmin(tup) \
308 ( \
309  HeapTupleHeaderXminFrozen(tup) ? \
310  FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
311 )
312 
313 #define HeapTupleHeaderSetXmin(tup, xid) \
314 ( \
315  (tup)->t_choice.t_heap.t_xmin = (xid) \
316 )
317 
318 #define HeapTupleHeaderXminCommitted(tup) \
319 ( \
320  ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
321 )
322 
323 #define HeapTupleHeaderXminInvalid(tup) \
324 ( \
325  ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
326  HEAP_XMIN_INVALID \
327 )
328 
329 #define HeapTupleHeaderXminFrozen(tup) \
330 ( \
331  ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
332 )
333 
334 #define HeapTupleHeaderSetXminCommitted(tup) \
335 ( \
336  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
337  ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
338 )
339 
340 #define HeapTupleHeaderSetXminInvalid(tup) \
341 ( \
342  AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
343  ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
344 )
345 
346 #define HeapTupleHeaderSetXminFrozen(tup) \
347 ( \
348  AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
349  ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
350 )
351 
352 /*
353  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid
354  * that updated a tuple, you might need to resolve the MultiXactId if certain
355  * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care
356  * to resolve the MultiXactId if necessary. This might involve multixact I/O,
357  * so it should only be used if absolutely necessary.
358  */
359 #define HeapTupleHeaderGetUpdateXid(tup) \
360 ( \
361  (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
362  ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
363  !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
364  HeapTupleGetUpdateXid(tup) \
365  : \
366  HeapTupleHeaderGetRawXmax(tup) \
367 )
368 
369 #define HeapTupleHeaderGetRawXmax(tup) \
370 ( \
371  (tup)->t_choice.t_heap.t_xmax \
372 )
373 
374 #define HeapTupleHeaderSetXmax(tup, xid) \
375 ( \
376  (tup)->t_choice.t_heap.t_xmax = (xid) \
377 )
378 
379 /*
380  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
381  * it is useful or not. Most code should use HeapTupleHeaderGetCmin or
382  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
383  * get a legitimate result, ie you are in the originating transaction!
384  */
385 #define HeapTupleHeaderGetRawCommandId(tup) \
386 ( \
387  (tup)->t_choice.t_heap.t_field3.t_cid \
388 )
389 
390 /* SetCmin is reasonably simple since we never need a combo CID */
391 #define HeapTupleHeaderSetCmin(tup, cid) \
392 do { \
393  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
394  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
395  (tup)->t_infomask &= ~HEAP_COMBOCID; \
396 } while (0)
397 
398 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
399 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
400 do { \
401  Assert(!((tup)->t_infomask & HEAP_MOVED)); \
402  (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
403  if (iscombo) \
404  (tup)->t_infomask |= HEAP_COMBOCID; \
405  else \
406  (tup)->t_infomask &= ~HEAP_COMBOCID; \
407 } while (0)
408 
409 #define HeapTupleHeaderGetXvac(tup) \
410 ( \
411  ((tup)->t_infomask & HEAP_MOVED) ? \
412  (tup)->t_choice.t_heap.t_field3.t_xvac \
413  : \
414  InvalidTransactionId \
415 )
416 
417 #define HeapTupleHeaderSetXvac(tup, xid) \
418 do { \
419  Assert((tup)->t_infomask & HEAP_MOVED); \
420  (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
421 } while (0)
422 
423 #define HeapTupleHeaderIsSpeculative(tup) \
424 ( \
425  (tup)->t_ctid.ip_posid == SpecTokenOffsetNumber \
426 )
427 
428 #define HeapTupleHeaderGetSpeculativeToken(tup) \
429 ( \
430  AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
431  ItemPointerGetBlockNumber(&(tup)->t_ctid) \
432 )
433 
434 #define HeapTupleHeaderSetSpeculativeToken(tup, token) \
435 ( \
436  ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
437 )
438 
439 #define HeapTupleHeaderGetDatumLength(tup) \
440  VARSIZE(tup)
441 
442 #define HeapTupleHeaderSetDatumLength(tup, len) \
443  SET_VARSIZE(tup, len)
444 
445 #define HeapTupleHeaderGetTypeId(tup) \
446 ( \
447  (tup)->t_choice.t_datum.datum_typeid \
448 )
449 
450 #define HeapTupleHeaderSetTypeId(tup, typeid) \
451 ( \
452  (tup)->t_choice.t_datum.datum_typeid = (typeid) \
453 )
454 
455 #define HeapTupleHeaderGetTypMod(tup) \
456 ( \
457  (tup)->t_choice.t_datum.datum_typmod \
458 )
459 
460 #define HeapTupleHeaderSetTypMod(tup, typmod) \
461 ( \
462  (tup)->t_choice.t_datum.datum_typmod = (typmod) \
463 )
464 
465 #define HeapTupleHeaderGetOid(tup) \
466 ( \
467  ((tup)->t_infomask & HEAP_HASOID) ? \
468  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
469  : \
470  InvalidOid \
471 )
472 
473 #define HeapTupleHeaderSetOid(tup, oid) \
474 do { \
475  Assert((tup)->t_infomask & HEAP_HASOID); \
476  *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) = (oid); \
477 } while (0)
478 
479 /*
480  * Note that we stop considering a tuple HOT-updated as soon as it is known
481  * aborted or the would-be updating transaction is known aborted. For best
482  * efficiency, check tuple visibility before using this macro, so that the
483  * INVALID bits will be as up to date as possible.
484  */
485 #define HeapTupleHeaderIsHotUpdated(tup) \
486 ( \
487  ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
488  ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
489  !HeapTupleHeaderXminInvalid(tup) \
490 )
491 
492 #define HeapTupleHeaderSetHotUpdated(tup) \
493 ( \
494  (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
495 )
496 
497 #define HeapTupleHeaderClearHotUpdated(tup) \
498 ( \
499  (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
500 )
501 
502 #define HeapTupleHeaderIsHeapOnly(tup) \
503 ( \
504  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
505 )
506 
507 #define HeapTupleHeaderSetHeapOnly(tup) \
508 ( \
509  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
510 )
511 
512 #define HeapTupleHeaderClearHeapOnly(tup) \
513 ( \
514  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
515 )
516 
517 #define HeapTupleHeaderHasMatch(tup) \
518 ( \
519  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
520 )
521 
522 #define HeapTupleHeaderSetMatch(tup) \
523 ( \
524  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
525 )
526 
527 #define HeapTupleHeaderClearMatch(tup) \
528 ( \
529  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
530 )
531 
532 #define HeapTupleHeaderGetNatts(tup) \
533  ((tup)->t_infomask2 & HEAP_NATTS_MASK)
534 
535 #define HeapTupleHeaderSetNatts(tup, natts) \
536 ( \
537  (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
538 )
539 
540 #define HeapTupleHeaderHasExternal(tup) \
541  (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
542 
543 
544 /*
545  * BITMAPLEN(NATTS) -
546  * Computes size of null bitmap given number of data columns.
547  */
548 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
549 
550 /*
551  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
552  * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the
553  * other stuff that has to be on a disk page. Since heap pages use no
554  * "special space", there's no deduction for that.
555  *
556  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
557  * an otherwise-empty page can indeed hold a tuple of this size. Because
558  * ItemIds and tuples have different alignment requirements, don't assume that
559  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
560  */
561 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
562 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader)
563 
564 /*
565  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
566  * fit on one heap page. (Note that indexes could have more, because they
567  * use a smaller tuple header.) We arrive at the divisor because each tuple
568  * must be maxaligned, and it must have an associated item pointer.
569  *
570  * Note: with HOT, there could theoretically be more line pointers (not actual
571  * tuples) than this on a heap page. However we constrain the number of line
572  * pointers to this anyway, to avoid excessive line-pointer bloat and not
573  * require increases in the size of work arrays.
574  */
575 #define MaxHeapTuplesPerPage \
576  ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
577  (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
578 
579 /*
580  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
581  * data fields of char(n) and similar types. It need not have anything
582  * directly to do with the *actual* upper limit of varlena values, which
583  * is currently 1Gb (see TOAST structures in postgres.h). I've set it
584  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
585  */
586 #define MaxAttrSize (10 * 1024 * 1024)
587 
588 
589 /*
590  * MinimalTuple is an alternative representation that is used for transient
591  * tuples inside the executor, in places where transaction status information
592  * is not required, the tuple rowtype is known, and shaving off a few bytes
593  * is worthwhile because we need to store many tuples. The representation
594  * is chosen so that tuple access routines can work with either full or
595  * minimal tuples via a HeapTupleData pointer structure. The access routines
596  * see no difference, except that they must not access the transaction status
597  * or t_ctid fields because those aren't there.
598  *
599  * For the most part, MinimalTuples should be accessed via TupleTableSlot
600  * routines. These routines will prevent access to the "system columns"
601  * and thereby prevent accidental use of the nonexistent fields.
602  *
603  * MinimalTupleData contains a length word, some padding, and fields matching
604  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
605  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
606  * structs. This makes data alignment rules equivalent in both cases.
607  *
608  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
609  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
610  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
611  * data would start. This trick is what makes the structs seem equivalent.
612  *
613  * Note that t_hoff is computed the same as in a full tuple, hence it includes
614  * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
615  *
616  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
617  * other than the length word. tuplesort.c and tuplestore.c use this to avoid
618  * writing the padding to disk.
619  */
620 #define MINIMAL_TUPLE_OFFSET \
621  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
622 #define MINIMAL_TUPLE_PADDING \
623  ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
624 #define MINIMAL_TUPLE_DATA_OFFSET \
625  offsetof(MinimalTupleData, t_infomask2)
626 
628 {
629  uint32 t_len; /* actual length of minimal tuple */
630 
632 
633  /* Fields below here must match HeapTupleHeaderData! */
634 
635  uint16 t_infomask2; /* number of attributes + various flags */
636 
637  uint16 t_infomask; /* various flag bits, see below */
638 
639  uint8 t_hoff; /* sizeof header incl. bitmap, padding */
640 
641  /* ^ - 23 bytes - ^ */
642 
643  bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */
644 
645  /* MORE DATA FOLLOWS AT END OF STRUCT */
646 };
647 
648 /* typedef appears in htup.h */
649 
650 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
651 
652 
653 /*
654  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
655  */
656 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
657 
658 /*
659  * Accessor macros to be used with HeapTuple pointers.
660  */
661 
662 #define HeapTupleHasNulls(tuple) \
663  (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
664 
665 #define HeapTupleNoNulls(tuple) \
666  (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
667 
668 #define HeapTupleHasVarWidth(tuple) \
669  (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
670 
671 #define HeapTupleAllFixed(tuple) \
672  (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
673 
674 #define HeapTupleHasExternal(tuple) \
675  (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
676 
677 #define HeapTupleIsHotUpdated(tuple) \
678  HeapTupleHeaderIsHotUpdated((tuple)->t_data)
679 
680 #define HeapTupleSetHotUpdated(tuple) \
681  HeapTupleHeaderSetHotUpdated((tuple)->t_data)
682 
683 #define HeapTupleClearHotUpdated(tuple) \
684  HeapTupleHeaderClearHotUpdated((tuple)->t_data)
685 
686 #define HeapTupleIsHeapOnly(tuple) \
687  HeapTupleHeaderIsHeapOnly((tuple)->t_data)
688 
689 #define HeapTupleSetHeapOnly(tuple) \
690  HeapTupleHeaderSetHeapOnly((tuple)->t_data)
691 
692 #define HeapTupleClearHeapOnly(tuple) \
693  HeapTupleHeaderClearHeapOnly((tuple)->t_data)
694 
695 #define HeapTupleGetOid(tuple) \
696  HeapTupleHeaderGetOid((tuple)->t_data)
697 
698 #define HeapTupleSetOid(tuple, oid) \
699  HeapTupleHeaderSetOid((tuple)->t_data, (oid))
700 
701 
702 /* ----------------
703  * fastgetattr
704  *
705  * Fetch a user attribute's value as a Datum (might be either a
706  * value, or a pointer into the data area of the tuple).
707  *
708  * This must not be used when a system attribute might be requested.
709  * Furthermore, the passed attnum MUST be valid. Use heap_getattr()
710  * instead, if in doubt.
711  *
712  * This gets called many times, so we macro the cacheable and NULL
713  * lookups, and call nocachegetattr() for the rest.
714  * ----------------
715  */
716 
717 #if !defined(DISABLE_COMPLEX_MACRO)
718 
719 #define fastgetattr(tup, attnum, tupleDesc, isnull) \
720 ( \
721  AssertMacro((attnum) > 0), \
722  (*(isnull) = false), \
723  HeapTupleNoNulls(tup) ? \
724  ( \
725  (tupleDesc)->attrs[(attnum)-1]->attcacheoff >= 0 ? \
726  ( \
727  fetchatt((tupleDesc)->attrs[(attnum)-1], \
728  (char *) (tup)->t_data + (tup)->t_data->t_hoff + \
729  (tupleDesc)->attrs[(attnum)-1]->attcacheoff) \
730  ) \
731  : \
732  nocachegetattr((tup), (attnum), (tupleDesc)) \
733  ) \
734  : \
735  ( \
736  att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \
737  ( \
738  (*(isnull) = true), \
739  (Datum)NULL \
740  ) \
741  : \
742  ( \
743  nocachegetattr((tup), (attnum), (tupleDesc)) \
744  ) \
745  ) \
746 )
747 #else /* defined(DISABLE_COMPLEX_MACRO) */
748 
749 extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
750  bool *isnull);
751 #endif /* defined(DISABLE_COMPLEX_MACRO) */
752 
753 
754 /* ----------------
755  * heap_getattr
756  *
757  * Extract an attribute of a heap tuple and return it as a Datum.
758  * This works for either system or user attributes. The given attnum
759  * is properly range-checked.
760  *
761  * If the field in question has a NULL value, we return a zero Datum
762  * and set *isnull == true. Otherwise, we set *isnull == false.
763  *
764  * <tup> is the pointer to the heap tuple. <attnum> is the attribute
765  * number of the column (field) caller wants. <tupleDesc> is a
766  * pointer to the structure describing the row and all its fields.
767  * ----------------
768  */
769 #define heap_getattr(tup, attnum, tupleDesc, isnull) \
770  ( \
771  ((attnum) > 0) ? \
772  ( \
773  ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
774  ( \
775  (*(isnull) = true), \
776  (Datum)NULL \
777  ) \
778  : \
779  fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \
780  ) \
781  : \
782  heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \
783  )
784 
785 
786 /* prototypes for functions in common/heaptuple.c */
788  Datum *values, bool *isnull);
790  Datum *values, bool *isnull,
791  char *data, Size data_size,
792  uint16 *infomask, bits8 *bit);
793 extern bool heap_attisnull(HeapTuple tup, int attnum);
794 extern Datum nocachegetattr(HeapTuple tup, int attnum,
795  TupleDesc att);
796 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
797  bool *isnull);
798 extern HeapTuple heap_copytuple(HeapTuple tuple);
799 extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest);
801 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
802  Datum *values, bool *isnull);
805  Datum *replValues,
806  bool *replIsnull,
807  bool *doReplace);
810  int nCols,
811  int *replCols,
812  Datum *replValues,
813  bool *replIsnull);
815  Datum *values, bool *isnull);
816 extern void heap_freetuple(HeapTuple htup);
817 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
818  Datum *values, bool *isnull);
819 extern void heap_free_minimal_tuple(MinimalTuple mtup);
823 
824 #endif /* HTUP_DETAILS_H */
uint32 CommandId
Definition: c.h:408
char mt_padding[MINIMAL_TUPLE_PADDING]
Definition: htup_details.h:631
#define fastgetattr(tup, attnum, tupleDesc, isnull)
Definition: htup_details.h:719
HeapTupleFields t_heap
Definition: htup_details.h:146
bool heap_attisnull(HeapTuple tup, int attnum)
Definition: heaptuple.c:297
uint32 TransactionId
Definition: c.h:394
bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]
Definition: htup_details.h:163
union HeapTupleHeaderData::@38 t_choice
Size heap_compute_data_size(TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:85
void heap_freetuple(HeapTuple htup)
Definition: heaptuple.c:1374
unsigned char uint8
Definition: c.h:263
HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1500
void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
Definition: heaptuple.c:634
struct DatumTupleFields DatumTupleFields
Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
Definition: heaptuple.c:552
unsigned int Oid
Definition: postgres_ext.h:31
DatumTupleFields t_datum
Definition: htup_details.h:147
bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]
Definition: htup_details.h:643
signed int int32
Definition: c.h:253
TransactionId t_xmax
Definition: htup_details.h:119
void heap_free_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1469
unsigned short uint16
Definition: c.h:264
HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *replValues, bool *replIsnull, bool *doReplace)
Definition: heaptuple.c:793
union HeapTupleFields::@37 t_field3
MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup)
Definition: heaptuple.c:1522
ItemPointerData t_ctid
Definition: htup_details.h:150
unsigned int uint32
Definition: c.h:265
TransactionId t_xmin
Definition: htup_details.h:118
#define MINIMAL_TUPLE_PADDING
Definition: htup_details.h:622
uint8 bits8
Definition: c.h:272
MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:1392
struct HeapTupleFields HeapTupleFields
uintptr_t Datum
Definition: postgres.h:374
TransactionId t_xvac
Definition: htup_details.h:124
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:935
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:692
MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup)
Definition: heaptuple.c:1481
HeapTuple heap_copytuple(HeapTuple tuple)
Definition: heaptuple.c:608
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull)
Definition: heaptuple.c:864
Datum bit(PG_FUNCTION_ARGS)
Definition: varbit.c:361
size_t Size
Definition: c.h:353
Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att)
Definition: heaptuple.c:352
static Datum values[MAXATTR]
Definition: bootstrap.c:162
void heap_fill_tuple(TupleDesc tupleDesc, Datum *values, bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit)
Definition: heaptuple.c:146
CommandId t_cid
Definition: htup_details.h:123
Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
Definition: heaptuple.c:656