src/include/access/htup_details.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * htup_details.h
   4  *        POSTGRES heap tuple header definitions.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/access/htup_details.h
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef HTUP_DETAILS_H
  15 #define HTUP_DETAILS_H
  16
  17 #include "access/htup.h"
  18 #include "access/transam.h"
  19 #include "access/tupdesc.h"
  20 #include "access/tupmacs.h"
  21 #include "storage/bufpage.h"
  22
  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_OLD is set in t_infomask, not created
  69  *          anymore)
  70  *                      user data fields
  71  *
  72  * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three
  73  * physical fields.  Xmin and Xmax are always really stored, but Cmin, Cmax
  74  * and Xvac share a field.  This works because we know that Cmin and Cmax
  75  * are only interesting for the lifetime of the inserting and deleting
  76  * transaction respectively.  If a tuple is inserted and deleted in the same
  77  * transaction, we store a "combo" command id that can be mapped to the real
  78  * cmin and cmax, but only by use of local state within the originating
  79  * backend.  See combocid.c for more details.  Meanwhile, Xvac is only set by
  80  * old-style VACUUM FULL, which does not have any command sub-structure and so
  81  * does not need either Cmin or Cmax.  (This requires that old-style VACUUM
  82  * FULL never try to move a tuple whose Cmin or Cmax is still interesting,
  83  * ie, an insert-in-progress or delete-in-progress tuple.)
  84  *
  85  * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
  86  * is initialized with its own TID (location).  If the tuple is ever updated,
  87  * its t_ctid is changed to point to the replacement version of the tuple.  Or
  88  * if the tuple is moved from one partition to another, due to an update of
  89  * the partition key, t_ctid is set to a special value to indicate that
  90  * (see ItemPointerSetMovedPartitions).  Thus, a tuple is the latest version
  91  * of its row iff XMAX is invalid or
  92  * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
  93  * either locked or deleted).  One can follow the chain of t_ctid links
  94  * to find the newest version of the row, unless it was moved to a different
  95  * partition.  Beware however that VACUUM might
  96  * erase the pointed-to (newer) tuple before erasing the pointing (older)
  97  * tuple.  Hence, when following a t_ctid link, it is necessary to check
  98  * to see if the referenced slot is empty or contains an unrelated tuple.
  99  * Check that the referenced tuple has XMIN equal to the referencing tuple's
 100  * XMAX to verify that it is actually the descendant version and not an
 101  * unrelated tuple stored into a slot recently freed by VACUUM.  If either
 102  * check fails, one may assume that there is no live descendant version.
 103  *
 104  * t_ctid is sometimes used to store a speculative insertion token, instead
 105  * of a real TID.  A speculative token is set on a tuple that's being
 106  * inserted, until the inserter is sure that it wants to go ahead with the
 107  * insertion.  Hence a token should only be seen on a tuple with an XMAX
 108  * that's still in-progress, or invalid/aborted.  The token is replaced with
 109  * the tuple's real TID when the insertion is confirmed.  One should never
 110  * see a speculative insertion token while following a chain of t_ctid links,
 111  * because they are not used on updates, only insertions.
 112  *
 113  * Following the fixed header fields, the nulls bitmap is stored (beginning
 114  * at t_bits).  The bitmap is *not* stored if t_infomask shows that there
 115  * are no nulls in the tuple.  If an OID field is present (as indicated by
 116  * t_infomask), then it is stored just before the user data, which begins at
 117  * the offset shown by t_hoff.  Note that t_hoff must be a multiple of
 118  * MAXALIGN.
 119  */
 120
 121 typedef struct HeapTupleFields
 122 {
 123         TransactionId t_xmin;           /* inserting xact ID */
 124         TransactionId t_xmax;           /* deleting or locking xact ID */
 125
 126         union
 127         {
 128                 CommandId       t_cid;          /* inserting or deleting command ID, or both */
 129                 TransactionId t_xvac;   /* old-style VACUUM FULL xact ID */
 130         }                       t_field3;
 131 } HeapTupleFields;
 132
 133 typedef struct DatumTupleFields
 134 {
 135         int32           datum_len_;             /* varlena header (do not touch directly!) */
 136
 137         int32           datum_typmod;   /* -1, or identifier of a record type */
 138
 139         Oid                     datum_typeid;   /* composite type OID, or RECORDOID */
 140
 141         /*
 142          * datum_typeid cannot be a domain over composite, only plain composite,
 143          * even if the datum is meant as a value of a domain-over-composite type.
 144          * This is in line with the general principle that CoerceToDomain does not
 145          * change the physical representation of the base type value.
 146          *
 147          * Note: field ordering is chosen with thought that Oid might someday
 148          * widen to 64 bits.
 149          */
 150 } DatumTupleFields;
 151
 152 struct HeapTupleHeaderData
 153 {
 154         union
 155         {
 156                 HeapTupleFields t_heap;
 157                 DatumTupleFields t_datum;
 158         }                       t_choice;
 159
 160         ItemPointerData t_ctid;         /* current TID of this or newer tuple (or a
 161                                                                  * speculative insertion token) */
 162
 163         /* Fields below here must match MinimalTupleData! */
 164
 165 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2
 166         uint16          t_infomask2;    /* number of attributes + various flags */
 167
 168 #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3
 169         uint16          t_infomask;             /* various flag bits, see below */
 170
 171 #define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4
 172         uint8           t_hoff;                 /* sizeof header incl. bitmap, padding */
 173
 174         /* ^ - 23 bytes - ^ */
 175
 176 #define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5
 177         bits8           t_bits[FLEXIBLE_ARRAY_MEMBER];  /* bitmap of NULLs */
 178
 179         /* MORE DATA FOLLOWS AT END OF STRUCT */
 180 };
 181
 182 /* typedef appears in htup.h */
 183
 184 #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)
 185
 186 /*
 187  * information stored in t_infomask:
 188  */
 189 #define HEAP_HASNULL                    0x0001  /* has null attribute(s) */
 190 #define HEAP_HASVARWIDTH                0x0002  /* has variable-width attribute(s) */
 191 #define HEAP_HASEXTERNAL                0x0004  /* has external stored attribute(s) */
 192 #define HEAP_HASOID_OLD                 0x0008  /* has an object-id field */
 193 #define HEAP_XMAX_KEYSHR_LOCK   0x0010  /* xmax is a key-shared locker */
 194 #define HEAP_COMBOCID                   0x0020  /* t_cid is a combo CID */
 195 #define HEAP_XMAX_EXCL_LOCK             0x0040  /* xmax is exclusive locker */
 196 #define HEAP_XMAX_LOCK_ONLY             0x0080  /* xmax, if valid, is only a locker */
 197
 198  /* xmax is a shared locker */
 199 #define HEAP_XMAX_SHR_LOCK      (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
 200
 201 #define HEAP_LOCK_MASK  (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
 202                                                  HEAP_XMAX_KEYSHR_LOCK)
 203 #define HEAP_XMIN_COMMITTED             0x0100  /* t_xmin committed */
 204 #define HEAP_XMIN_INVALID               0x0200  /* t_xmin invalid/aborted */
 205 #define HEAP_XMIN_FROZEN                (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
 206 #define HEAP_XMAX_COMMITTED             0x0400  /* t_xmax committed */
 207 #define HEAP_XMAX_INVALID               0x0800  /* t_xmax invalid/aborted */
 208 #define HEAP_XMAX_IS_MULTI              0x1000  /* t_xmax is a MultiXactId */
 209 #define HEAP_UPDATED                    0x2000  /* this is UPDATEd version of row */
 210 #define HEAP_MOVED_OFF                  0x4000  /* moved to another place by pre-9.0
 211                                                                                  * VACUUM FULL; kept for binary
 212                                                                                  * upgrade support */
 213 #define HEAP_MOVED_IN                   0x8000  /* moved from another place by pre-9.0
 214                                                                                  * VACUUM FULL; kept for binary
 215                                                                                  * upgrade support */
 216 #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
 217
 218 #define HEAP_XACT_MASK                  0xFFF0  /* visibility-related bits */
 219
 220 /*
 221  * A tuple is only locked (i.e. not updated by its Xmax) if the
 222  * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is
 223  * not a multi and the EXCL_LOCK bit is set.
 224  *
 225  * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible
 226  * aborted updater transaction.
 227  *
 228  * Beware of multiple evaluations of the argument.
 229  */
 230 #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \
 231         (((infomask) & HEAP_XMAX_LOCK_ONLY) || \
 232          (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))
 233
 234 /*
 235  * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of
 236  * HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_KEYSHR_LOCK must come from a tuple that was
 237  * share-locked in 9.2 or earlier and then pg_upgrade'd.
 238  *
 239  * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple
 240  * FOR SHARE lockers of that tuple.  That set HEAP_XMAX_LOCK_ONLY (with a
 241  * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and
 242  * HEAP_XMAX_KEYSHR_LOCK.  That combination is no longer possible in 9.3 and
 243  * up, so if we see that combination we know for certain that the tuple was
 244  * locked in an earlier release; since all such lockers are gone (they cannot
 245  * survive through pg_upgrade), such tuples can safely be considered not
 246  * locked.
 247  *
 248  * We must not resolve such multixacts locally, because the result would be
 249  * bogus, regardless of where they stand with respect to the current valid
 250  * multixact range.
 251  */
 252 #define HEAP_LOCKED_UPGRADED(infomask) \
 253 ( \
 254          ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \
 255          ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \
 256          (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \
 257 )
 258
 259 /*
 260  * Use these to test whether a particular lock is applied to a tuple
 261  */
 262 #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \
 263         (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)
 264 #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \
 265         (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)
 266 #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \
 267         (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)
 268
 269 /* turn these all off when Xmax is to change */
 270 #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \
 271                                                 HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)
 272
 273 /*
 274  * information stored in t_infomask2:
 275  */
 276 #define HEAP_NATTS_MASK                 0x07FF  /* 11 bits for number of attributes */
 277 /* bits 0x1800 are available */
 278 #define HEAP_KEYS_UPDATED               0x2000  /* tuple was updated and key cols
 279                                                                                  * modified, or tuple deleted */
 280 #define HEAP_HOT_UPDATED                0x4000  /* tuple was HOT-updated */
 281 #define HEAP_ONLY_TUPLE                 0x8000  /* this is heap-only tuple */
 282
 283 #define HEAP2_XACT_MASK                 0xE000  /* visibility-related bits */
 284
 285 /*
 286  * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins.  It is
 287  * only used in tuples that are in the hash table, and those don't need
 288  * any visibility information, so we can overlay it on a visibility flag
 289  * instead of using up a dedicated bit.
 290  */
 291 #define HEAP_TUPLE_HAS_MATCH    HEAP_ONLY_TUPLE /* tuple has a join match */
 292
 293 /*
 294  * HeapTupleHeader accessor macros
 295  *
 296  * Note: beware of multiple evaluations of "tup" argument.  But the Set
 297  * macros evaluate their other argument only once.
 298  */
 299
 300 /*
 301  * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid
 302  * originally used to insert the tuple.  However, the tuple might actually
 303  * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin
 304  * is visible to every snapshot.  Prior to PostgreSQL 9.4, we actually changed
 305  * the xmin to FrozenTransactionId, and that value may still be encountered
 306  * on disk.
 307  */
 308 #define HeapTupleHeaderGetRawXmin(tup) \
 309 ( \
 310         (tup)->t_choice.t_heap.t_xmin \
 311 )
 312
 313 #define HeapTupleHeaderGetXmin(tup) \
 314 ( \
 315         HeapTupleHeaderXminFrozen(tup) ? \
 316                 FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \
 317 )
 318
 319 #define HeapTupleHeaderSetXmin(tup, xid) \
 320 ( \
 321         (tup)->t_choice.t_heap.t_xmin = (xid) \
 322 )
 323
 324 #define HeapTupleHeaderXminCommitted(tup) \
 325 ( \
 326         ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \
 327 )
 328
 329 #define HeapTupleHeaderXminInvalid(tup) \
 330 ( \
 331         ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \
 332                 HEAP_XMIN_INVALID \
 333 )
 334
 335 #define HeapTupleHeaderXminFrozen(tup) \
 336 ( \
 337         ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \
 338 )
 339
 340 #define HeapTupleHeaderSetXminCommitted(tup) \
 341 ( \
 342         AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
 343         ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \
 344 )
 345
 346 #define HeapTupleHeaderSetXminInvalid(tup) \
 347 ( \
 348         AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \
 349         ((tup)->t_infomask |= HEAP_XMIN_INVALID) \
 350 )
 351
 352 #define HeapTupleHeaderSetXminFrozen(tup) \
 353 ( \
 354         AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \
 355         ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \
 356 )
 357
 358 /*
 359  * HeapTupleHeaderGetRawXmax gets you the raw Xmax field.  To find out the Xid
 360  * that updated a tuple, you might need to resolve the MultiXactId if certain
 361  * bits are set.  HeapTupleHeaderGetUpdateXid checks those bits and takes care
 362  * to resolve the MultiXactId if necessary.  This might involve multixact I/O,
 363  * so it should only be used if absolutely necessary.
 364  */
 365 #define HeapTupleHeaderGetUpdateXid(tup) \
 366 ( \
 367         (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \
 368          ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \
 369          !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \
 370                 HeapTupleGetUpdateXid(tup) \
 371         : \
 372                 HeapTupleHeaderGetRawXmax(tup) \
 373 )
 374
 375 #define HeapTupleHeaderGetRawXmax(tup) \
 376 ( \
 377         (tup)->t_choice.t_heap.t_xmax \
 378 )
 379
 380 #define HeapTupleHeaderSetXmax(tup, xid) \
 381 ( \
 382         (tup)->t_choice.t_heap.t_xmax = (xid) \
 383 )
 384
 385 /*
 386  * HeapTupleHeaderGetRawCommandId will give you what's in the header whether
 387  * it is useful or not.  Most code should use HeapTupleHeaderGetCmin or
 388  * HeapTupleHeaderGetCmax instead, but note that those Assert that you can
 389  * get a legitimate result, ie you are in the originating transaction!
 390  */
 391 #define HeapTupleHeaderGetRawCommandId(tup) \
 392 ( \
 393         (tup)->t_choice.t_heap.t_field3.t_cid \
 394 )
 395
 396 /* SetCmin is reasonably simple since we never need a combo CID */
 397 #define HeapTupleHeaderSetCmin(tup, cid) \
 398 do { \
 399         Assert(!((tup)->t_infomask & HEAP_MOVED)); \
 400         (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
 401         (tup)->t_infomask &= ~HEAP_COMBOCID; \
 402 } while (0)
 403
 404 /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */
 405 #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \
 406 do { \
 407         Assert(!((tup)->t_infomask & HEAP_MOVED)); \
 408         (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \
 409         if (iscombo) \
 410                 (tup)->t_infomask |= HEAP_COMBOCID; \
 411         else \
 412                 (tup)->t_infomask &= ~HEAP_COMBOCID; \
 413 } while (0)
 414
 415 #define HeapTupleHeaderGetXvac(tup) \
 416 ( \
 417         ((tup)->t_infomask & HEAP_MOVED) ? \
 418                 (tup)->t_choice.t_heap.t_field3.t_xvac \
 419         : \
 420                 InvalidTransactionId \
 421 )
 422
 423 #define HeapTupleHeaderSetXvac(tup, xid) \
 424 do { \
 425         Assert((tup)->t_infomask & HEAP_MOVED); \
 426         (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \
 427 } while (0)
 428
 429 #define HeapTupleHeaderIsSpeculative(tup) \
 430 ( \
 431         (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \
 432 )
 433
 434 #define HeapTupleHeaderGetSpeculativeToken(tup) \
 435 ( \
 436         AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \
 437         ItemPointerGetBlockNumber(&(tup)->t_ctid) \
 438 )
 439
 440 #define HeapTupleHeaderSetSpeculativeToken(tup, token)  \
 441 ( \
 442         ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
 443 )
 444
 445 #define HeapTupleHeaderIndicatesMovedPartitions(tup) \
 446         ItemPointerIndicatesMovedPartitions(&(tup)->t_ctid)
 447
 448 #define HeapTupleHeaderSetMovedPartitions(tup) \
 449         ItemPointerSetMovedPartitions(&(tup)->t_ctid)
 450
 451 #define HeapTupleHeaderGetDatumLength(tup) \
 452         VARSIZE(tup)
 453
 454 #define HeapTupleHeaderSetDatumLength(tup, len) \
 455         SET_VARSIZE(tup, len)
 456
 457 #define HeapTupleHeaderGetTypeId(tup) \
 458 ( \
 459         (tup)->t_choice.t_datum.datum_typeid \
 460 )
 461
 462 #define HeapTupleHeaderSetTypeId(tup, typeid) \
 463 ( \
 464         (tup)->t_choice.t_datum.datum_typeid = (typeid) \
 465 )
 466
 467 #define HeapTupleHeaderGetTypMod(tup) \
 468 ( \
 469         (tup)->t_choice.t_datum.datum_typmod \
 470 )
 471
 472 #define HeapTupleHeaderSetTypMod(tup, typmod) \
 473 ( \
 474         (tup)->t_choice.t_datum.datum_typmod = (typmod) \
 475 )
 476
 477 /*
 478  * Note that we stop considering a tuple HOT-updated as soon as it is known
 479  * aborted or the would-be updating transaction is known aborted.  For best
 480  * efficiency, check tuple visibility before using this macro, so that the
 481  * INVALID bits will be as up to date as possible.
 482  */
 483 #define HeapTupleHeaderIsHotUpdated(tup) \
 484 ( \
 485         ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \
 486         ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \
 487         !HeapTupleHeaderXminInvalid(tup) \
 488 )
 489
 490 #define HeapTupleHeaderSetHotUpdated(tup) \
 491 ( \
 492         (tup)->t_infomask2 |= HEAP_HOT_UPDATED \
 493 )
 494
 495 #define HeapTupleHeaderClearHotUpdated(tup) \
 496 ( \
 497         (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \
 498 )
 499
 500 #define HeapTupleHeaderIsHeapOnly(tup) \
 501 ( \
 502   ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \
 503 )
 504
 505 #define HeapTupleHeaderSetHeapOnly(tup) \
 506 ( \
 507   (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \
 508 )
 509
 510 #define HeapTupleHeaderClearHeapOnly(tup) \
 511 ( \
 512   (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \
 513 )
 514
 515 #define HeapTupleHeaderHasMatch(tup) \
 516 ( \
 517   ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \
 518 )
 519
 520 #define HeapTupleHeaderSetMatch(tup) \
 521 ( \
 522   (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \
 523 )
 524
 525 #define HeapTupleHeaderClearMatch(tup) \
 526 ( \
 527   (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \
 528 )
 529
 530 #define HeapTupleHeaderGetNatts(tup) \
 531         ((tup)->t_infomask2 & HEAP_NATTS_MASK)
 532
 533 #define HeapTupleHeaderSetNatts(tup, natts) \
 534 ( \
 535         (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
 536 )
 537
 538 #define HeapTupleHeaderHasExternal(tup) \
 539                 (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)
 540
 541
 542 /*
 543  * BITMAPLEN(NATTS) -
 544  *              Computes size of null bitmap given number of data columns.
 545  */
 546 #define BITMAPLEN(NATTS)        (((int)(NATTS) + 7) / 8)
 547
 548 /*
 549  * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including
 550  * header and MAXALIGN alignment padding.  Basically it's BLCKSZ minus the
 551  * other stuff that has to be on a disk page.  Since heap pages use no
 552  * "special space", there's no deduction for that.
 553  *
 554  * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
 555  * an otherwise-empty page can indeed hold a tuple of this size.  Because
 556  * ItemIds and tuples have different alignment requirements, don't assume that
 557  * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
 558  */
 559 #define MaxHeapTupleSize  (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
 560 #define MinHeapTupleSize  MAXALIGN(SizeofHeapTupleHeader)
 561
 562 /*
 563  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
 564  * fit on one heap page.  (Note that indexes could have more, because they
 565  * use a smaller tuple header.)  We arrive at the divisor because each tuple
 566  * must be maxaligned, and it must have an associated line pointer.
 567  *
 568  * Note: with HOT, there could theoretically be more line pointers (not actual
 569  * tuples) than this on a heap page.  However we constrain the number of line
 570  * pointers to this anyway, to avoid excessive line-pointer bloat and not
 571  * require increases in the size of work arrays.
 572  */
 573 #define MaxHeapTuplesPerPage    \
 574         ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
 575                         (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))
 576
 577 /*
 578  * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
 579  * data fields of char(n) and similar types.  It need not have anything
 580  * directly to do with the *actual* upper limit of varlena values, which
 581  * is currently 1Gb (see TOAST structures in postgres.h).  I've set it
 582  * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
 583  */
 584 #define MaxAttrSize             (10 * 1024 * 1024)
 585
 586
 587 /*
 588  * MinimalTuple is an alternative representation that is used for transient
 589  * tuples inside the executor, in places where transaction status information
 590  * is not required, the tuple rowtype is known, and shaving off a few bytes
 591  * is worthwhile because we need to store many tuples.  The representation
 592  * is chosen so that tuple access routines can work with either full or
 593  * minimal tuples via a HeapTupleData pointer structure.  The access routines
 594  * see no difference, except that they must not access the transaction status
 595  * or t_ctid fields because those aren't there.
 596  *
 597  * For the most part, MinimalTuples should be accessed via TupleTableSlot
 598  * routines.  These routines will prevent access to the "system columns"
 599  * and thereby prevent accidental use of the nonexistent fields.
 600  *
 601  * MinimalTupleData contains a length word, some padding, and fields matching
 602  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so
 603  * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both
 604  * structs.   This makes data alignment rules equivalent in both cases.
 605  *
 606  * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
 607  * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the
 608  * minimal tuple --- that is, where a full tuple matching the minimal tuple's
 609  * data would start.  This trick is what makes the structs seem equivalent.
 610  *
 611  * Note that t_hoff is computed the same as in a full tuple, hence it includes
 612  * the MINIMAL_TUPLE_OFFSET distance.  t_len does not include that, however.
 613  *
 614  * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
 615  * other than the length word.  tuplesort.c and tuplestore.c use this to avoid
 616  * writing the padding to disk.
 617  */
 618 #define MINIMAL_TUPLE_OFFSET \
 619         ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
 620 #define MINIMAL_TUPLE_PADDING \
 621         ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
 622 #define MINIMAL_TUPLE_DATA_OFFSET \
 623         offsetof(MinimalTupleData, t_infomask2)
 624
 625 struct MinimalTupleData
 626 {
 627         uint32          t_len;                  /* actual length of minimal tuple */
 628
 629         char            mt_padding[MINIMAL_TUPLE_PADDING];
 630
 631         /* Fields below here must match HeapTupleHeaderData! */
 632
 633         uint16          t_infomask2;    /* number of attributes + various flags */
 634
 635         uint16          t_infomask;             /* various flag bits, see below */
 636
 637         uint8           t_hoff;                 /* sizeof header incl. bitmap, padding */
 638
 639         /* ^ - 23 bytes - ^ */
 640
 641         bits8           t_bits[FLEXIBLE_ARRAY_MEMBER];  /* bitmap of NULLs */
 642
 643         /* MORE DATA FOLLOWS AT END OF STRUCT */
 644 };
 645
 646 /* typedef appears in htup.h */
 647
 648 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)
 649
 650
 651 /*
 652  * GETSTRUCT - given a HeapTuple pointer, return address of the user data
 653  */
 654 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)
 655
 656 /*
 657  * Accessor macros to be used with HeapTuple pointers.
 658  */
 659
 660 #define HeapTupleHasNulls(tuple) \
 661                 (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)
 662
 663 #define HeapTupleNoNulls(tuple) \
 664                 (!((tuple)->t_data->t_infomask & HEAP_HASNULL))
 665
 666 #define HeapTupleHasVarWidth(tuple) \
 667                 (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)
 668
 669 #define HeapTupleAllFixed(tuple) \
 670                 (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))
 671
 672 #define HeapTupleHasExternal(tuple) \
 673                 (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)
 674
 675 #define HeapTupleIsHotUpdated(tuple) \
 676                 HeapTupleHeaderIsHotUpdated((tuple)->t_data)
 677
 678 #define HeapTupleSetHotUpdated(tuple) \
 679                 HeapTupleHeaderSetHotUpdated((tuple)->t_data)
 680
 681 #define HeapTupleClearHotUpdated(tuple) \
 682                 HeapTupleHeaderClearHotUpdated((tuple)->t_data)
 683
 684 #define HeapTupleIsHeapOnly(tuple) \
 685                 HeapTupleHeaderIsHeapOnly((tuple)->t_data)
 686
 687 #define HeapTupleSetHeapOnly(tuple) \
 688                 HeapTupleHeaderSetHeapOnly((tuple)->t_data)
 689
 690 #define HeapTupleClearHeapOnly(tuple) \
 691                 HeapTupleHeaderClearHeapOnly((tuple)->t_data)
 692
 693
 694 /* ----------------
 695  *              fastgetattr
 696  *
 697  *              Fetch a user attribute's value as a Datum (might be either a
 698  *              value, or a pointer into the data area of the tuple).
 699  *
 700  *              This must not be used when a system attribute might be requested.
 701  *              Furthermore, the passed attnum MUST be valid.  Use heap_getattr()
 702  *              instead, if in doubt.
 703  *
 704  *              This gets called many times, so we macro the cacheable and NULL
 705  *              lookups, and call nocachegetattr() for the rest.
 706  * ----------------
 707  */
 708
 709 #if !defined(DISABLE_COMPLEX_MACRO)
 710
 711 #define fastgetattr(tup, attnum, tupleDesc, isnull)                                     \
 712 (                                                                                                                                       \
 713         AssertMacro((attnum) > 0),                                                                              \
 714         (*(isnull) = false),                                                                                    \
 715         HeapTupleNoNulls(tup) ?                                                                                 \
 716         (                                                                                                                               \
 717                 TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ?      \
 718                 (                                                                                                                       \
 719                         fetchatt(TupleDescAttr((tupleDesc), (attnum)-1),                \
 720                                 (char *) (tup)->t_data + (tup)->t_data->t_hoff +        \
 721                                 TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\
 722                 )                                                                                                                       \
 723                 :                                                                                                                       \
 724                         nocachegetattr((tup), (attnum), (tupleDesc))                    \
 725         )                                                                                                                               \
 726         :                                                                                                                               \
 727         (                                                                                                                               \
 728                 att_isnull((attnum)-1, (tup)->t_data->t_bits) ?                         \
 729                 (                                                                                                                       \
 730                         (*(isnull) = true),                                                                             \
 731                         (Datum)NULL                                                                                             \
 732                 )                                                                                                                       \
 733                 :                                                                                                                       \
 734                 (                                                                                                                       \
 735                         nocachegetattr((tup), (attnum), (tupleDesc))                    \
 736                 )                                                                                                                       \
 737         )                                                                                                                               \
 738 )
 739 #else                                                   /* defined(DISABLE_COMPLEX_MACRO) */
 740
 741 extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
 742                                                  bool *isnull);
 743 #endif                                                  /* defined(DISABLE_COMPLEX_MACRO) */
 744
 745
 746 /* ----------------
 747  *              heap_getattr
 748  *
 749  *              Extract an attribute of a heap tuple and return it as a Datum.
 750  *              This works for either system or user attributes.  The given attnum
 751  *              is properly range-checked.
 752  *
 753  *              If the field in question has a NULL value, we return a zero Datum
 754  *              and set *isnull == true.  Otherwise, we set *isnull == false.
 755  *
 756  *              <tup> is the pointer to the heap tuple.  <attnum> is the attribute
 757  *              number of the column (field) caller wants.  <tupleDesc> is a
 758  *              pointer to the structure describing the row and all its fields.
 759  * ----------------
 760  */
 761 #define heap_getattr(tup, attnum, tupleDesc, isnull) \
 762         ( \
 763                 ((attnum) > 0) ? \
 764                 ( \
 765                         ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
 766                                 getmissingattr((tupleDesc), (attnum), (isnull)) \
 767                         : \
 768                                 fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \
 769                 ) \
 770                 : \
 771                         heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \
 772         )
 773
 774
 775 /* prototypes for functions in common/heaptuple.c */
 776 extern Size heap_compute_data_size(TupleDesc tupleDesc,
 777                                                                    Datum *values, bool *isnull);
 778 extern void heap_fill_tuple(TupleDesc tupleDesc,
 779                                                         Datum *values, bool *isnull,
 780                                                         char *data, Size data_size,
 781                                                         uint16 *infomask, bits8 *bit);
 782 extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);
 783 extern Datum nocachegetattr(HeapTuple tup, int attnum,
 784                                                         TupleDesc att);
 785 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
 786                                                          bool *isnull);
 787 extern Datum getmissingattr(TupleDesc tupleDesc,
 788                                                         int attnum, bool *isnull);
 789 extern HeapTuple heap_copytuple(HeapTuple tuple);
 790 extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest);
 791 extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);
 792 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
 793                                                                  Datum *values, bool *isnull);
 794 extern HeapTuple heap_modify_tuple(HeapTuple tuple,
 795                                                                    TupleDesc tupleDesc,
 796                                                                    Datum *replValues,
 797                                                                    bool *replIsnull,
 798                                                                    bool *doReplace);
 799 extern HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple,
 800                                                                                    TupleDesc tupleDesc,
 801                                                                                    int nCols,
 802                                                                                    int *replCols,
 803                                                                                    Datum *replValues,
 804                                                                                    bool *replIsnull);
 805 extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
 806                                                           Datum *values, bool *isnull);
 807 extern void heap_freetuple(HeapTuple htup);
 808 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,
 809                                                                                         Datum *values, bool *isnull);
 810 extern void heap_free_minimal_tuple(MinimalTuple mtup);
 811 extern MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup);
 812 extern HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup);
 813 extern MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup);
 814 extern size_t varsize_any(void *p);
 815 extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
 816 extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);
 817
 818 #endif                                                  /* HTUP_DETAILS_H */