1 /*------------------------------------------------------------------------- 2 * 3 * htup_details.h 4 * POSTGRES heap tuple header definitions. 5 * 6 * 7 * Portions Copyright (c) 1996-2020, 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 (ItemPointerGetOffsetNumber(&(tup)->t_ctid) == MovedPartitionsOffsetNumber && \ 447 ItemPointerGetBlockNumberNoCheck(&(tup)->t_ctid) == MovedPartitionsBlockNumber) 448 449 #define HeapTupleHeaderSetMovedPartitions(tup) \ 450 ItemPointerSet(&(tup)->t_ctid, MovedPartitionsBlockNumber, MovedPartitionsOffsetNumber) 451 452 #define HeapTupleHeaderGetDatumLength(tup) \ 453 VARSIZE(tup) 454 455 #define HeapTupleHeaderSetDatumLength(tup, len) \ 456 SET_VARSIZE(tup, len) 457 458 #define HeapTupleHeaderGetTypeId(tup) \ 459 ( \ 460 (tup)->t_choice.t_datum.datum_typeid \ 461 ) 462 463 #define HeapTupleHeaderSetTypeId(tup, typeid) \ 464 ( \ 465 (tup)->t_choice.t_datum.datum_typeid = (typeid) \ 466 ) 467 468 #define HeapTupleHeaderGetTypMod(tup) \ 469 ( \ 470 (tup)->t_choice.t_datum.datum_typmod \ 471 ) 472 473 #define HeapTupleHeaderSetTypMod(tup, typmod) \ 474 ( \ 475 (tup)->t_choice.t_datum.datum_typmod = (typmod) \ 476 ) 477 478 /* 479 * Note that we stop considering a tuple HOT-updated as soon as it is known 480 * aborted or the would-be updating transaction is known aborted. For best 481 * efficiency, check tuple visibility before using this macro, so that the 482 * INVALID bits will be as up to date as possible. 483 */ 484 #define HeapTupleHeaderIsHotUpdated(tup) \ 485 ( \ 486 ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \ 487 ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \ 488 !HeapTupleHeaderXminInvalid(tup) \ 489 ) 490 491 #define HeapTupleHeaderSetHotUpdated(tup) \ 492 ( \ 493 (tup)->t_infomask2 |= HEAP_HOT_UPDATED \ 494 ) 495 496 #define HeapTupleHeaderClearHotUpdated(tup) \ 497 ( \ 498 (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \ 499 ) 500 501 #define HeapTupleHeaderIsHeapOnly(tup) \ 502 ( \ 503 ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \ 504 ) 505 506 #define HeapTupleHeaderSetHeapOnly(tup) \ 507 ( \ 508 (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \ 509 ) 510 511 #define HeapTupleHeaderClearHeapOnly(tup) \ 512 ( \ 513 (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \ 514 ) 515 516 #define HeapTupleHeaderHasMatch(tup) \ 517 ( \ 518 ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \ 519 ) 520 521 #define HeapTupleHeaderSetMatch(tup) \ 522 ( \ 523 (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \ 524 ) 525 526 #define HeapTupleHeaderClearMatch(tup) \ 527 ( \ 528 (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \ 529 ) 530 531 #define HeapTupleHeaderGetNatts(tup) \ 532 ((tup)->t_infomask2 & HEAP_NATTS_MASK) 533 534 #define HeapTupleHeaderSetNatts(tup, natts) \ 535 ( \ 536 (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \ 537 ) 538 539 #define HeapTupleHeaderHasExternal(tup) \ 540 (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0) 541 542 543 /* 544 * BITMAPLEN(NATTS) - 545 * Computes size of null bitmap given number of data columns. 546 */ 547 #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8) 548 549 /* 550 * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including 551 * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the 552 * other stuff that has to be on a disk page. Since heap pages use no 553 * "special space", there's no deduction for that. 554 * 555 * NOTE: we allow for the ItemId that must point to the tuple, ensuring that 556 * an otherwise-empty page can indeed hold a tuple of this size. Because 557 * ItemIds and tuples have different alignment requirements, don't assume that 558 * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page. 559 */ 560 #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData))) 561 #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader) 562 563 /* 564 * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can 565 * fit on one heap page. (Note that indexes could have more, because they 566 * use a smaller tuple header.) We arrive at the divisor because each tuple 567 * must be maxaligned, and it must have an associated line pointer. 568 * 569 * Note: with HOT, there could theoretically be more line pointers (not actual 570 * tuples) than this on a heap page. However we constrain the number of line 571 * pointers to this anyway, to avoid excessive line-pointer bloat and not 572 * require increases in the size of work arrays. 573 */ 574 #define MaxHeapTuplesPerPage \ 575 ((int) ((BLCKSZ - SizeOfPageHeaderData) / \ 576 (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData)))) 577 578 /* 579 * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of 580 * data fields of char(n) and similar types. It need not have anything 581 * directly to do with the *actual* upper limit of varlena values, which 582 * is currently 1Gb (see TOAST structures in postgres.h). I've set it 583 * at 10Mb which seems like a reasonable number --- tgl 8/6/00. 584 */ 585 #define MaxAttrSize (10 * 1024 * 1024) 586 587 588 /* 589 * MinimalTuple is an alternative representation that is used for transient 590 * tuples inside the executor, in places where transaction status information 591 * is not required, the tuple rowtype is known, and shaving off a few bytes 592 * is worthwhile because we need to store many tuples. The representation 593 * is chosen so that tuple access routines can work with either full or 594 * minimal tuples via a HeapTupleData pointer structure. The access routines 595 * see no difference, except that they must not access the transaction status 596 * or t_ctid fields because those aren't there. 597 * 598 * For the most part, MinimalTuples should be accessed via TupleTableSlot 599 * routines. These routines will prevent access to the "system columns" 600 * and thereby prevent accidental use of the nonexistent fields. 601 * 602 * MinimalTupleData contains a length word, some padding, and fields matching 603 * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so 604 * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both 605 * structs. This makes data alignment rules equivalent in both cases. 606 * 607 * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is 608 * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the 609 * minimal tuple --- that is, where a full tuple matching the minimal tuple's 610 * data would start. This trick is what makes the structs seem equivalent. 611 * 612 * Note that t_hoff is computed the same as in a full tuple, hence it includes 613 * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however. 614 * 615 * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data 616 * other than the length word. tuplesort.c and tuplestore.c use this to avoid 617 * writing the padding to disk. 618 */ 619 #define MINIMAL_TUPLE_OFFSET \ 620 ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF) 621 #define MINIMAL_TUPLE_PADDING \ 622 ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF) 623 #define MINIMAL_TUPLE_DATA_OFFSET \ 624 offsetof(MinimalTupleData, t_infomask2) 625 626 struct MinimalTupleData 627 { 628 uint32 t_len; /* actual length of minimal tuple */ 629 630 char mt_padding[MINIMAL_TUPLE_PADDING]; 631 632 /* Fields below here must match HeapTupleHeaderData! */ 633 634 uint16 t_infomask2; /* number of attributes + various flags */ 635 636 uint16 t_infomask; /* various flag bits, see below */ 637 638 uint8 t_hoff; /* sizeof header incl. bitmap, padding */ 639 640 /* ^ - 23 bytes - ^ */ 641 642 bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */ 643 644 /* MORE DATA FOLLOWS AT END OF STRUCT */ 645 }; 646 647 /* typedef appears in htup.h */ 648 649 #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits) 650 651 652 /* 653 * GETSTRUCT - given a HeapTuple pointer, return address of the user data 654 */ 655 #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff) 656 657 /* 658 * Accessor macros to be used with HeapTuple pointers. 659 */ 660 661 #define HeapTupleHasNulls(tuple) \ 662 (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0) 663 664 #define HeapTupleNoNulls(tuple) \ 665 (!((tuple)->t_data->t_infomask & HEAP_HASNULL)) 666 667 #define HeapTupleHasVarWidth(tuple) \ 668 (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0) 669 670 #define HeapTupleAllFixed(tuple) \ 671 (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH)) 672 673 #define HeapTupleHasExternal(tuple) \ 674 (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0) 675 676 #define HeapTupleIsHotUpdated(tuple) \ 677 HeapTupleHeaderIsHotUpdated((tuple)->t_data) 678 679 #define HeapTupleSetHotUpdated(tuple) \ 680 HeapTupleHeaderSetHotUpdated((tuple)->t_data) 681 682 #define HeapTupleClearHotUpdated(tuple) \ 683 HeapTupleHeaderClearHotUpdated((tuple)->t_data) 684 685 #define HeapTupleIsHeapOnly(tuple) \ 686 HeapTupleHeaderIsHeapOnly((tuple)->t_data) 687 688 #define HeapTupleSetHeapOnly(tuple) \ 689 HeapTupleHeaderSetHeapOnly((tuple)->t_data) 690 691 #define HeapTupleClearHeapOnly(tuple) \ 692 HeapTupleHeaderClearHeapOnly((tuple)->t_data) 693 694 695 /* ---------------- 696 * fastgetattr 697 * 698 * Fetch a user attribute's value as a Datum (might be either a 699 * value, or a pointer into the data area of the tuple). 700 * 701 * This must not be used when a system attribute might be requested. 702 * Furthermore, the passed attnum MUST be valid. Use heap_getattr() 703 * instead, if in doubt. 704 * 705 * This gets called many times, so we macro the cacheable and NULL 706 * lookups, and call nocachegetattr() for the rest. 707 * ---------------- 708 */ 709 710 #if !defined(DISABLE_COMPLEX_MACRO) 711 712 #define fastgetattr(tup, attnum, tupleDesc, isnull) \ 713 ( \ 714 AssertMacro((attnum) > 0), \ 715 (*(isnull) = false), \ 716 HeapTupleNoNulls(tup) ? \ 717 ( \ 718 TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \ 719 ( \ 720 fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \ 721 (char *) (tup)->t_data + (tup)->t_data->t_hoff + \ 722 TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\ 723 ) \ 724 : \ 725 nocachegetattr((tup), (attnum), (tupleDesc)) \ 726 ) \ 727 : \ 728 ( \ 729 att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \ 730 ( \ 731 (*(isnull) = true), \ 732 (Datum)NULL \ 733 ) \ 734 : \ 735 ( \ 736 nocachegetattr((tup), (attnum), (tupleDesc)) \ 737 ) \ 738 ) \ 739 ) 740 #else /* defined(DISABLE_COMPLEX_MACRO) */ 741 742 extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, 743 bool *isnull); 744 #endif /* defined(DISABLE_COMPLEX_MACRO) */ 745 746 747 /* ---------------- 748 * heap_getattr 749 * 750 * Extract an attribute of a heap tuple and return it as a Datum. 751 * This works for either system or user attributes. The given attnum 752 * is properly range-checked. 753 * 754 * If the field in question has a NULL value, we return a zero Datum 755 * and set *isnull == true. Otherwise, we set *isnull == false. 756 * 757 * <tup> is the pointer to the heap tuple. <attnum> is the attribute 758 * number of the column (field) caller wants. <tupleDesc> is a 759 * pointer to the structure describing the row and all its fields. 760 * ---------------- 761 */ 762 #define heap_getattr(tup, attnum, tupleDesc, isnull) \ 763 ( \ 764 ((attnum) > 0) ? \ 765 ( \ 766 ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \ 767 getmissingattr((tupleDesc), (attnum), (isnull)) \ 768 : \ 769 fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \ 770 ) \ 771 : \ 772 heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \ 773 ) 774 775 776 /* prototypes for functions in common/heaptuple.c */ 777 extern Size heap_compute_data_size(TupleDesc tupleDesc, 778 Datum *values, bool *isnull); 779 extern void heap_fill_tuple(TupleDesc tupleDesc, 780 Datum *values, bool *isnull, 781 char *data, Size data_size, 782 uint16 *infomask, bits8 *bit); 783 extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc); 784 extern Datum nocachegetattr(HeapTuple tup, int attnum, 785 TupleDesc att); 786 extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, 787 bool *isnull); 788 extern Datum getmissingattr(TupleDesc tupleDesc, 789 int attnum, bool *isnull); 790 extern HeapTuple heap_copytuple(HeapTuple tuple); 791 extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest); 792 extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc); 793 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, 794 Datum *values, bool *isnull); 795 extern HeapTuple heap_modify_tuple(HeapTuple tuple, 796 TupleDesc tupleDesc, 797 Datum *replValues, 798 bool *replIsnull, 799 bool *doReplace); 800 extern HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, 801 TupleDesc tupleDesc, 802 int nCols, 803 int *replCols, 804 Datum *replValues, 805 bool *replIsnull); 806 extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, 807 Datum *values, bool *isnull); 808 extern void heap_freetuple(HeapTuple htup); 809 extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, 810 Datum *values, bool *isnull); 811 extern void heap_free_minimal_tuple(MinimalTuple mtup); 812 extern MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup); 813 extern HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup); 814 extern MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup); 815 extern size_t varsize_any(void *p); 816 extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc); 817 extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc); 818 819 #endif /* HTUP_DETAILS_H */ 820