codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * htup_details.h4 *	  POSTGRES heap tuple header definitions.5 *6 *7 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group8 * Portions Copyright (c) 1994, Regents of the University of California9 *10 * src/include/access/htup_details.h11 *12 *-------------------------------------------------------------------------13 */14#ifndef HTUP_DETAILS_H15#define HTUP_DETAILS_H16 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#include "varatt.h"23 24/*25 * MaxTupleAttributeNumber limits the number of (user) columns in a tuple.26 * The key limit on this value is that the size of the fixed overhead for27 * a tuple, plus the size of the null-values bitmap (at 1 bit per column),28 * plus MAXALIGN alignment, must fit into t_hoff which is uint8.  On most29 * machines the upper limit without making t_hoff wider would be a little30 * over 1700.  We use round numbers here and for MaxHeapAttributeNumber31 * so that alterations in HeapTupleHeaderData layout won't change the32 * supported max number of columns.33 */34#define MaxTupleAttributeNumber 1664	/* 8 * 208 */35 36/*37 * MaxHeapAttributeNumber limits the number of (user) columns in a table.38 * This should be somewhat less than MaxTupleAttributeNumber.  It must be39 * at least one less, else we will fail to do UPDATEs on a maximal-width40 * table (because UPDATE has to form working tuples that include CTID).41 * In practice we want some additional daylight so that we can gracefully42 * support operations that add hidden "resjunk" columns, for example43 * SELECT * FROM wide_table ORDER BY foo, bar, baz.44 * In any case, depending on column data types you will likely be running45 * into the disk-block-based limit on overall tuple size if you have more46 * than a thousand or so columns.  TOAST won't help.47 */48#define MaxHeapAttributeNumber	1600	/* 8 * 200 */49 50/*51 * Heap tuple header.  To avoid wasting space, the fields should be52 * laid out in such a way as to avoid structure padding.53 *54 * Datums of composite types (row types) share the same general structure55 * as on-disk tuples, so that the same routines can be used to build and56 * examine them.  However the requirements are slightly different: a Datum57 * does not need any transaction visibility information, and it does need58 * a length word and some embedded type information.  We can achieve this59 * by overlaying the xmin/cmin/xmax/cmax/xvac fields of a heap tuple60 * with the fields needed in the Datum case.  Typically, all tuples built61 * in-memory will be initialized with the Datum fields; but when a tuple is62 * about to be inserted in a table, the transaction fields will be filled,63 * overwriting the datum fields.64 *65 * The overall structure of a heap tuple looks like:66 *			fixed fields (HeapTupleHeaderData struct)67 *			nulls bitmap (if HEAP_HASNULL is set in t_infomask)68 *			alignment padding (as needed to make user data MAXALIGN'd)69 *			object ID (if HEAP_HASOID_OLD is set in t_infomask, not created70 *          anymore)71 *			user data fields72 *73 * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three74 * physical fields.  Xmin and Xmax are always really stored, but Cmin, Cmax75 * and Xvac share a field.  This works because we know that Cmin and Cmax76 * are only interesting for the lifetime of the inserting and deleting77 * transaction respectively.  If a tuple is inserted and deleted in the same78 * transaction, we store a "combo" command id that can be mapped to the real79 * cmin and cmax, but only by use of local state within the originating80 * backend.  See combocid.c for more details.  Meanwhile, Xvac is only set by81 * old-style VACUUM FULL, which does not have any command sub-structure and so82 * does not need either Cmin or Cmax.  (This requires that old-style VACUUM83 * FULL never try to move a tuple whose Cmin or Cmax is still interesting,84 * ie, an insert-in-progress or delete-in-progress tuple.)85 *86 * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid87 * is initialized with its own TID (location).  If the tuple is ever updated,88 * its t_ctid is changed to point to the replacement version of the tuple.  Or89 * if the tuple is moved from one partition to another, due to an update of90 * the partition key, t_ctid is set to a special value to indicate that91 * (see ItemPointerSetMovedPartitions).  Thus, a tuple is the latest version92 * of its row iff XMAX is invalid or93 * t_ctid points to itself (in which case, if XMAX is valid, the tuple is94 * either locked or deleted).  One can follow the chain of t_ctid links95 * to find the newest version of the row, unless it was moved to a different96 * partition.  Beware however that VACUUM might97 * erase the pointed-to (newer) tuple before erasing the pointing (older)98 * tuple.  Hence, when following a t_ctid link, it is necessary to check99 * to see if the referenced slot is empty or contains an unrelated tuple.100 * Check that the referenced tuple has XMIN equal to the referencing tuple's101 * XMAX to verify that it is actually the descendant version and not an102 * unrelated tuple stored into a slot recently freed by VACUUM.  If either103 * check fails, one may assume that there is no live descendant version.104 *105 * t_ctid is sometimes used to store a speculative insertion token, instead106 * of a real TID.  A speculative token is set on a tuple that's being107 * inserted, until the inserter is sure that it wants to go ahead with the108 * insertion.  Hence a token should only be seen on a tuple with an XMAX109 * that's still in-progress, or invalid/aborted.  The token is replaced with110 * the tuple's real TID when the insertion is confirmed.  One should never111 * see a speculative insertion token while following a chain of t_ctid links,112 * because they are not used on updates, only insertions.113 *114 * Following the fixed header fields, the nulls bitmap is stored (beginning115 * at t_bits).  The bitmap is *not* stored if t_infomask shows that there116 * are no nulls in the tuple.  If an OID field is present (as indicated by117 * t_infomask), then it is stored just before the user data, which begins at118 * the offset shown by t_hoff.  Note that t_hoff must be a multiple of119 * MAXALIGN.120 */121 122typedef struct HeapTupleFields123{124	TransactionId t_xmin;		/* inserting xact ID */125	TransactionId t_xmax;		/* deleting or locking xact ID */126 127	union128	{129		CommandId	t_cid;		/* inserting or deleting command ID, or both */130		TransactionId t_xvac;	/* old-style VACUUM FULL xact ID */131	}			t_field3;132} HeapTupleFields;133 134typedef struct DatumTupleFields135{136	int32		datum_len_;		/* varlena header (do not touch directly!) */137 138	int32		datum_typmod;	/* -1, or identifier of a record type */139 140	Oid			datum_typeid;	/* composite type OID, or RECORDOID */141 142	/*143	 * datum_typeid cannot be a domain over composite, only plain composite,144	 * even if the datum is meant as a value of a domain-over-composite type.145	 * This is in line with the general principle that CoerceToDomain does not146	 * change the physical representation of the base type value.147	 *148	 * Note: field ordering is chosen with thought that Oid might someday149	 * widen to 64 bits.150	 */151} DatumTupleFields;152 153struct HeapTupleHeaderData154{155	union156	{157		HeapTupleFields t_heap;158		DatumTupleFields t_datum;159	}			t_choice;160 161	ItemPointerData t_ctid;		/* current TID of this or newer tuple (or a162								 * speculative insertion token) */163 164	/* Fields below here must match MinimalTupleData! */165 166#define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2167	uint16		t_infomask2;	/* number of attributes + various flags */168 169#define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3170	uint16		t_infomask;		/* various flag bits, see below */171 172#define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4173	uint8		t_hoff;			/* sizeof header incl. bitmap, padding */174 175	/* ^ - 23 bytes - ^ */176 177#define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5178	bits8		t_bits[FLEXIBLE_ARRAY_MEMBER];	/* bitmap of NULLs */179 180	/* MORE DATA FOLLOWS AT END OF STRUCT */181};182 183/* typedef appears in htup.h */184 185#define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits)186 187/*188 * information stored in t_infomask:189 */190#define HEAP_HASNULL			0x0001	/* has null attribute(s) */191#define HEAP_HASVARWIDTH		0x0002	/* has variable-width attribute(s) */192#define HEAP_HASEXTERNAL		0x0004	/* has external stored attribute(s) */193#define HEAP_HASOID_OLD			0x0008	/* has an object-id field */194#define HEAP_XMAX_KEYSHR_LOCK	0x0010	/* xmax is a key-shared locker */195#define HEAP_COMBOCID			0x0020	/* t_cid is a combo CID */196#define HEAP_XMAX_EXCL_LOCK		0x0040	/* xmax is exclusive locker */197#define HEAP_XMAX_LOCK_ONLY		0x0080	/* xmax, if valid, is only a locker */198 199 /* xmax is a shared locker */200#define HEAP_XMAX_SHR_LOCK	(HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)201 202#define HEAP_LOCK_MASK	(HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \203						 HEAP_XMAX_KEYSHR_LOCK)204#define HEAP_XMIN_COMMITTED		0x0100	/* t_xmin committed */205#define HEAP_XMIN_INVALID		0x0200	/* t_xmin invalid/aborted */206#define HEAP_XMIN_FROZEN		(HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)207#define HEAP_XMAX_COMMITTED		0x0400	/* t_xmax committed */208#define HEAP_XMAX_INVALID		0x0800	/* t_xmax invalid/aborted */209#define HEAP_XMAX_IS_MULTI		0x1000	/* t_xmax is a MultiXactId */210#define HEAP_UPDATED			0x2000	/* this is UPDATEd version of row */211#define HEAP_MOVED_OFF			0x4000	/* moved to another place by pre-9.0212										 * VACUUM FULL; kept for binary213										 * upgrade support */214#define HEAP_MOVED_IN			0x8000	/* moved from another place by pre-9.0215										 * VACUUM FULL; kept for binary216										 * upgrade support */217#define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)218 219#define HEAP_XACT_MASK			0xFFF0	/* visibility-related bits */220 221/*222 * A tuple is only locked (i.e. not updated by its Xmax) if the223 * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is224 * not a multi and the EXCL_LOCK bit is set.225 *226 * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible227 * aborted updater transaction.228 *229 * Beware of multiple evaluations of the argument.230 */231#define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \232	(((infomask) & HEAP_XMAX_LOCK_ONLY) || \233	 (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK))234 235/*236 * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of237 * HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_KEYSHR_LOCK must come from a tuple that was238 * share-locked in 9.2 or earlier and then pg_upgrade'd.239 *240 * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple241 * FOR SHARE lockers of that tuple.  That set HEAP_XMAX_LOCK_ONLY (with a242 * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and243 * HEAP_XMAX_KEYSHR_LOCK.  That combination is no longer possible in 9.3 and244 * up, so if we see that combination we know for certain that the tuple was245 * locked in an earlier release; since all such lockers are gone (they cannot246 * survive through pg_upgrade), such tuples can safely be considered not247 * locked.248 *249 * We must not resolve such multixacts locally, because the result would be250 * bogus, regardless of where they stand with respect to the current valid251 * multixact range.252 */253#define HEAP_LOCKED_UPGRADED(infomask) \254( \255	 ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \256	 ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \257	 (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \258)259 260/*261 * Use these to test whether a particular lock is applied to a tuple262 */263#define HEAP_XMAX_IS_SHR_LOCKED(infomask) \264	(((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)265#define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \266	(((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)267#define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \268	(((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)269 270/* turn these all off when Xmax is to change */271#define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \272						HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY)273 274/*275 * information stored in t_infomask2:276 */277#define HEAP_NATTS_MASK			0x07FF	/* 11 bits for number of attributes */278/* bits 0x1800 are available */279#define HEAP_KEYS_UPDATED		0x2000	/* tuple was updated and key cols280										 * modified, or tuple deleted */281#define HEAP_HOT_UPDATED		0x4000	/* tuple was HOT-updated */282#define HEAP_ONLY_TUPLE			0x8000	/* this is heap-only tuple */283 284#define HEAP2_XACT_MASK			0xE000	/* visibility-related bits */285 286/*287 * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins.  It is288 * only used in tuples that are in the hash table, and those don't need289 * any visibility information, so we can overlay it on a visibility flag290 * instead of using up a dedicated bit.291 */292#define HEAP_TUPLE_HAS_MATCH	HEAP_ONLY_TUPLE /* tuple has a join match */293 294/*295 * HeapTupleHeader accessor macros296 *297 * Note: beware of multiple evaluations of "tup" argument.  But the Set298 * macros evaluate their other argument only once.299 */300 301/*302 * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid303 * originally used to insert the tuple.  However, the tuple might actually304 * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin305 * is visible to every snapshot.  Prior to PostgreSQL 9.4, we actually changed306 * the xmin to FrozenTransactionId, and that value may still be encountered307 * on disk.308 */309#define HeapTupleHeaderGetRawXmin(tup) \310( \311	(tup)->t_choice.t_heap.t_xmin \312)313 314#define HeapTupleHeaderGetXmin(tup) \315( \316	HeapTupleHeaderXminFrozen(tup) ? \317		FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \318)319 320#define HeapTupleHeaderSetXmin(tup, xid) \321( \322	(tup)->t_choice.t_heap.t_xmin = (xid) \323)324 325#define HeapTupleHeaderXminCommitted(tup) \326( \327	((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \328)329 330#define HeapTupleHeaderXminInvalid(tup) \331( \332	((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \333		HEAP_XMIN_INVALID \334)335 336#define HeapTupleHeaderXminFrozen(tup) \337( \338	((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \339)340 341#define HeapTupleHeaderSetXminCommitted(tup) \342( \343	AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \344	((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \345)346 347#define HeapTupleHeaderSetXminInvalid(tup) \348( \349	AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \350	((tup)->t_infomask |= HEAP_XMIN_INVALID) \351)352 353#define HeapTupleHeaderSetXminFrozen(tup) \354( \355	AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \356	((tup)->t_infomask |= HEAP_XMIN_FROZEN) \357)358 359/*360 * HeapTupleHeaderGetRawXmax gets you the raw Xmax field.  To find out the Xid361 * that updated a tuple, you might need to resolve the MultiXactId if certain362 * bits are set.  HeapTupleHeaderGetUpdateXid checks those bits and takes care363 * to resolve the MultiXactId if necessary.  This might involve multixact I/O,364 * so it should only be used if absolutely necessary.365 */366#define HeapTupleHeaderGetUpdateXid(tup) \367( \368	(!((tup)->t_infomask & HEAP_XMAX_INVALID) && \369	 ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \370	 !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \371		HeapTupleGetUpdateXid(tup) \372	: \373		HeapTupleHeaderGetRawXmax(tup) \374)375 376#define HeapTupleHeaderGetRawXmax(tup) \377( \378	(tup)->t_choice.t_heap.t_xmax \379)380 381#define HeapTupleHeaderSetXmax(tup, xid) \382( \383	(tup)->t_choice.t_heap.t_xmax = (xid) \384)385 386/*387 * HeapTupleHeaderGetRawCommandId will give you what's in the header whether388 * it is useful or not.  Most code should use HeapTupleHeaderGetCmin or389 * HeapTupleHeaderGetCmax instead, but note that those Assert that you can390 * get a legitimate result, ie you are in the originating transaction!391 */392#define HeapTupleHeaderGetRawCommandId(tup) \393( \394	(tup)->t_choice.t_heap.t_field3.t_cid \395)396 397/* SetCmin is reasonably simple since we never need a combo CID */398#define HeapTupleHeaderSetCmin(tup, cid) \399do { \400	Assert(!((tup)->t_infomask & HEAP_MOVED)); \401	(tup)->t_choice.t_heap.t_field3.t_cid = (cid); \402	(tup)->t_infomask &= ~HEAP_COMBOCID; \403} while (0)404 405/* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */406#define HeapTupleHeaderSetCmax(tup, cid, iscombo) \407do { \408	Assert(!((tup)->t_infomask & HEAP_MOVED)); \409	(tup)->t_choice.t_heap.t_field3.t_cid = (cid); \410	if (iscombo) \411		(tup)->t_infomask |= HEAP_COMBOCID; \412	else \413		(tup)->t_infomask &= ~HEAP_COMBOCID; \414} while (0)415 416#define HeapTupleHeaderGetXvac(tup) \417( \418	((tup)->t_infomask & HEAP_MOVED) ? \419		(tup)->t_choice.t_heap.t_field3.t_xvac \420	: \421		InvalidTransactionId \422)423 424#define HeapTupleHeaderSetXvac(tup, xid) \425do { \426	Assert((tup)->t_infomask & HEAP_MOVED); \427	(tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \428} while (0)429 430StaticAssertDecl(MaxOffsetNumber < SpecTokenOffsetNumber,431				 "invalid speculative token constant");432 433#define HeapTupleHeaderIsSpeculative(tup) \434( \435	(ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \436)437 438#define HeapTupleHeaderGetSpeculativeToken(tup) \439( \440	AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \441	ItemPointerGetBlockNumber(&(tup)->t_ctid) \442)443 444#define HeapTupleHeaderSetSpeculativeToken(tup, token)	\445( \446	ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \447)448 449#define HeapTupleHeaderIndicatesMovedPartitions(tup) \450	ItemPointerIndicatesMovedPartitions(&(tup)->t_ctid)451 452#define HeapTupleHeaderSetMovedPartitions(tup) \453	ItemPointerSetMovedPartitions(&(tup)->t_ctid)454 455#define HeapTupleHeaderGetDatumLength(tup) \456	VARSIZE(tup)457 458#define HeapTupleHeaderSetDatumLength(tup, len) \459	SET_VARSIZE(tup, len)460 461#define HeapTupleHeaderGetTypeId(tup) \462( \463	(tup)->t_choice.t_datum.datum_typeid \464)465 466#define HeapTupleHeaderSetTypeId(tup, typeid) \467( \468	(tup)->t_choice.t_datum.datum_typeid = (typeid) \469)470 471#define HeapTupleHeaderGetTypMod(tup) \472( \473	(tup)->t_choice.t_datum.datum_typmod \474)475 476#define HeapTupleHeaderSetTypMod(tup, typmod) \477( \478	(tup)->t_choice.t_datum.datum_typmod = (typmod) \479)480 481/*482 * Note that we stop considering a tuple HOT-updated as soon as it is known483 * aborted or the would-be updating transaction is known aborted.  For best484 * efficiency, check tuple visibility before using this macro, so that the485 * INVALID bits will be as up to date as possible.486 */487#define HeapTupleHeaderIsHotUpdated(tup) \488( \489	((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \490	((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \491	!HeapTupleHeaderXminInvalid(tup) \492)493 494#define HeapTupleHeaderSetHotUpdated(tup) \495( \496	(tup)->t_infomask2 |= HEAP_HOT_UPDATED \497)498 499#define HeapTupleHeaderClearHotUpdated(tup) \500( \501	(tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \502)503 504#define HeapTupleHeaderIsHeapOnly(tup) \505( \506  ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \507)508 509#define HeapTupleHeaderSetHeapOnly(tup) \510( \511  (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \512)513 514#define HeapTupleHeaderClearHeapOnly(tup) \515( \516  (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \517)518 519#define HeapTupleHeaderHasMatch(tup) \520( \521  ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \522)523 524#define HeapTupleHeaderSetMatch(tup) \525( \526  (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \527)528 529#define HeapTupleHeaderClearMatch(tup) \530( \531  (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \532)533 534#define HeapTupleHeaderGetNatts(tup) \535	((tup)->t_infomask2 & HEAP_NATTS_MASK)536 537#define HeapTupleHeaderSetNatts(tup, natts) \538( \539	(tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \540)541 542#define HeapTupleHeaderHasExternal(tup) \543		(((tup)->t_infomask & HEAP_HASEXTERNAL) != 0)544 545 546/*547 * BITMAPLEN(NATTS) -548 *		Computes size of null bitmap given number of data columns.549 */550#define BITMAPLEN(NATTS)	(((int)(NATTS) + 7) / 8)551 552/*553 * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including554 * header and MAXALIGN alignment padding.  Basically it's BLCKSZ minus the555 * other stuff that has to be on a disk page.  Since heap pages use no556 * "special space", there's no deduction for that.557 *558 * NOTE: we allow for the ItemId that must point to the tuple, ensuring that559 * an otherwise-empty page can indeed hold a tuple of this size.  Because560 * ItemIds and tuples have different alignment requirements, don't assume that561 * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.562 */563#define MaxHeapTupleSize  (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))564#define MinHeapTupleSize  MAXALIGN(SizeofHeapTupleHeader)565 566/*567 * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can568 * fit on one heap page.  (Note that indexes could have more, because they569 * use a smaller tuple header.)  We arrive at the divisor because each tuple570 * must be maxaligned, and it must have an associated line pointer.571 *572 * Note: with HOT, there could theoretically be more line pointers (not actual573 * tuples) than this on a heap page.  However we constrain the number of line574 * pointers to this anyway, to avoid excessive line-pointer bloat and not575 * require increases in the size of work arrays.576 */577#define MaxHeapTuplesPerPage	\578	((int) ((BLCKSZ - SizeOfPageHeaderData) / \579			(MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData))))580 581/*582 * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of583 * data fields of char(n) and similar types.  It need not have anything584 * directly to do with the *actual* upper limit of varlena values, which585 * is currently 1Gb (see TOAST structures in postgres.h).  I've set it586 * at 10Mb which seems like a reasonable number --- tgl 8/6/00.587 */588#define MaxAttrSize		(10 * 1024 * 1024)589 590 591/*592 * MinimalTuple is an alternative representation that is used for transient593 * tuples inside the executor, in places where transaction status information594 * is not required, the tuple rowtype is known, and shaving off a few bytes595 * is worthwhile because we need to store many tuples.  The representation596 * is chosen so that tuple access routines can work with either full or597 * minimal tuples via a HeapTupleData pointer structure.  The access routines598 * see no difference, except that they must not access the transaction status599 * or t_ctid fields because those aren't there.600 *601 * For the most part, MinimalTuples should be accessed via TupleTableSlot602 * routines.  These routines will prevent access to the "system columns"603 * and thereby prevent accidental use of the nonexistent fields.604 *605 * MinimalTupleData contains a length word, some padding, and fields matching606 * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so607 * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both608 * structs.   This makes data alignment rules equivalent in both cases.609 *610 * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is611 * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the612 * minimal tuple --- that is, where a full tuple matching the minimal tuple's613 * data would start.  This trick is what makes the structs seem equivalent.614 *615 * Note that t_hoff is computed the same as in a full tuple, hence it includes616 * the MINIMAL_TUPLE_OFFSET distance.  t_len does not include that, however.617 *618 * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data619 * other than the length word.  tuplesort.c and tuplestore.c use this to avoid620 * writing the padding to disk.621 */622#define MINIMAL_TUPLE_OFFSET \623	((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)624#define MINIMAL_TUPLE_PADDING \625	((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)626#define MINIMAL_TUPLE_DATA_OFFSET \627	offsetof(MinimalTupleData, t_infomask2)628 629struct MinimalTupleData630{631	uint32		t_len;			/* actual length of minimal tuple */632 633	char		mt_padding[MINIMAL_TUPLE_PADDING];634 635	/* Fields below here must match HeapTupleHeaderData! */636 637	uint16		t_infomask2;	/* number of attributes + various flags */638 639	uint16		t_infomask;		/* various flag bits, see below */640 641	uint8		t_hoff;			/* sizeof header incl. bitmap, padding */642 643	/* ^ - 23 bytes - ^ */644 645	bits8		t_bits[FLEXIBLE_ARRAY_MEMBER];	/* bitmap of NULLs */646 647	/* MORE DATA FOLLOWS AT END OF STRUCT */648};649 650/* typedef appears in htup.h */651 652#define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits)653 654 655/*656 * GETSTRUCT - given a HeapTuple pointer, return address of the user data657 */658#define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)659 660/*661 * Accessor macros to be used with HeapTuple pointers.662 */663 664#define HeapTupleHasNulls(tuple) \665		(((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)666 667#define HeapTupleNoNulls(tuple) \668		(!((tuple)->t_data->t_infomask & HEAP_HASNULL))669 670#define HeapTupleHasVarWidth(tuple) \671		(((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)672 673#define HeapTupleAllFixed(tuple) \674		(!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))675 676#define HeapTupleHasExternal(tuple) \677		(((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)678 679#define HeapTupleIsHotUpdated(tuple) \680		HeapTupleHeaderIsHotUpdated((tuple)->t_data)681 682#define HeapTupleSetHotUpdated(tuple) \683		HeapTupleHeaderSetHotUpdated((tuple)->t_data)684 685#define HeapTupleClearHotUpdated(tuple) \686		HeapTupleHeaderClearHotUpdated((tuple)->t_data)687 688#define HeapTupleIsHeapOnly(tuple) \689		HeapTupleHeaderIsHeapOnly((tuple)->t_data)690 691#define HeapTupleSetHeapOnly(tuple) \692		HeapTupleHeaderSetHeapOnly((tuple)->t_data)693 694#define HeapTupleClearHeapOnly(tuple) \695		HeapTupleHeaderClearHeapOnly((tuple)->t_data)696 697/* prototypes for functions in common/heaptuple.c */698extern Size heap_compute_data_size(TupleDesc tupleDesc,699								   Datum *values, bool *isnull);700extern void heap_fill_tuple(TupleDesc tupleDesc,701							Datum *values, bool *isnull,702							char *data, Size data_size,703							uint16 *infomask, bits8 *bit);704extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc);705extern Datum nocachegetattr(HeapTuple tup, int attnum,706							TupleDesc tupleDesc);707extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,708							 bool *isnull);709extern Datum getmissingattr(TupleDesc tupleDesc,710							int attnum, bool *isnull);711extern HeapTuple heap_copytuple(HeapTuple tuple);712extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest);713extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);714extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,715								 Datum *values, bool *isnull);716extern HeapTuple heap_modify_tuple(HeapTuple tuple,717								   TupleDesc tupleDesc,718								   Datum *replValues,719								   bool *replIsnull,720								   bool *doReplace);721extern HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple,722										   TupleDesc tupleDesc,723										   int nCols,724										   int *replCols,725										   Datum *replValues,726										   bool *replIsnull);727extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,728							  Datum *values, bool *isnull);729extern void heap_freetuple(HeapTuple htup);730extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor,731											Datum *values, bool *isnull);732extern void heap_free_minimal_tuple(MinimalTuple mtup);733extern MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup);734extern HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup);735extern MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup);736extern size_t varsize_any(void *p);737extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);738extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc);739 740#ifndef FRONTEND741/*742 *	fastgetattr743 *		Fetch a user attribute's value as a Datum (might be either a744 *		value, or a pointer into the data area of the tuple).745 *746 *		This must not be used when a system attribute might be requested.747 *		Furthermore, the passed attnum MUST be valid.  Use heap_getattr()748 *		instead, if in doubt.749 *750 *		This gets called many times, so we macro the cacheable and NULL751 *		lookups, and call nocachegetattr() for the rest.752 */753static inline Datum754fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)755{756	Assert(attnum > 0);757 758	*isnull = false;759	if (HeapTupleNoNulls(tup))760	{761		Form_pg_attribute att;762 763		att = TupleDescAttr(tupleDesc, attnum - 1);764		if (att->attcacheoff >= 0)765			return fetchatt(att, (char *) tup->t_data + tup->t_data->t_hoff +766							att->attcacheoff);767		else768			return nocachegetattr(tup, attnum, tupleDesc);769	}770	else771	{772		if (att_isnull(attnum - 1, tup->t_data->t_bits))773		{774			*isnull = true;775			return (Datum) NULL;776		}777		else778			return nocachegetattr(tup, attnum, tupleDesc);779	}780}781 782/*783 *	heap_getattr784 *		Extract an attribute of a heap tuple and return it as a Datum.785 *		This works for either system or user attributes.  The given attnum786 *		is properly range-checked.787 *788 *		If the field in question has a NULL value, we return a zero Datum789 *		and set *isnull == true.  Otherwise, we set *isnull == false.790 *791 *		<tup> is the pointer to the heap tuple.  <attnum> is the attribute792 *		number of the column (field) caller wants.  <tupleDesc> is a793 *		pointer to the structure describing the row and all its fields.794 *795 */796static inline Datum797heap_getattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)798{799	if (attnum > 0)800	{801		if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))802			return getmissingattr(tupleDesc, attnum, isnull);803		else804			return fastgetattr(tup, attnum, tupleDesc, isnull);805	}806	else807		return heap_getsysattr(tup, attnum, tupleDesc, isnull);808}809#endif							/* FRONTEND */810 811#endif							/* HTUP_DETAILS_H */812