codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * itemid.h4 *	  Standard POSTGRES buffer page item identifier/line pointer 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/storage/itemid.h11 *12 *-------------------------------------------------------------------------13 */14#ifndef ITEMID_H15#define ITEMID_H16 17/*18 * A line pointer on a buffer page.  See buffer page definitions and comments19 * for an explanation of how line pointers are used.20 *21 * In some cases a line pointer is "in use" but does not have any associated22 * storage on the page.  By convention, lp_len == 0 in every line pointer23 * that does not have storage, independently of its lp_flags state.24 */25typedef struct ItemIdData26{27	unsigned	lp_off:15,		/* offset to tuple (from start of page) */28				lp_flags:2,		/* state of line pointer, see below */29				lp_len:15;		/* byte length of tuple */30} ItemIdData;31 32typedef ItemIdData *ItemId;33 34/*35 * lp_flags has these possible states.  An UNUSED line pointer is available36 * for immediate re-use, the other states are not.37 */38#define LP_UNUSED		0		/* unused (should always have lp_len=0) */39#define LP_NORMAL		1		/* used (should always have lp_len>0) */40#define LP_REDIRECT		2		/* HOT redirect (should have lp_len=0) */41#define LP_DEAD			3		/* dead, may or may not have storage */42 43/*44 * Item offsets and lengths are represented by these types when45 * they're not actually stored in an ItemIdData.46 */47typedef uint16 ItemOffset;48typedef uint16 ItemLength;49 50 51/* ----------------52 *		support macros53 * ----------------54 */55 56/*57 *		ItemIdGetLength58 */59#define ItemIdGetLength(itemId) \60   ((itemId)->lp_len)61 62/*63 *		ItemIdGetOffset64 */65#define ItemIdGetOffset(itemId) \66   ((itemId)->lp_off)67 68/*69 *		ItemIdGetFlags70 */71#define ItemIdGetFlags(itemId) \72   ((itemId)->lp_flags)73 74/*75 *		ItemIdGetRedirect76 * In a REDIRECT pointer, lp_off holds offset number for next line pointer77 */78#define ItemIdGetRedirect(itemId) \79   ((itemId)->lp_off)80 81/*82 * ItemIdIsValid83 *		True iff item identifier is valid.84 *		This is a pretty weak test, probably useful only in Asserts.85 */86#define ItemIdIsValid(itemId)	PointerIsValid(itemId)87 88/*89 * ItemIdIsUsed90 *		True iff item identifier is in use.91 */92#define ItemIdIsUsed(itemId) \93	((itemId)->lp_flags != LP_UNUSED)94 95/*96 * ItemIdIsNormal97 *		True iff item identifier is in state NORMAL.98 */99#define ItemIdIsNormal(itemId) \100	((itemId)->lp_flags == LP_NORMAL)101 102/*103 * ItemIdIsRedirected104 *		True iff item identifier is in state REDIRECT.105 */106#define ItemIdIsRedirected(itemId) \107	((itemId)->lp_flags == LP_REDIRECT)108 109/*110 * ItemIdIsDead111 *		True iff item identifier is in state DEAD.112 */113#define ItemIdIsDead(itemId) \114	((itemId)->lp_flags == LP_DEAD)115 116/*117 * ItemIdHasStorage118 *		True iff item identifier has associated storage.119 */120#define ItemIdHasStorage(itemId) \121	((itemId)->lp_len != 0)122 123/*124 * ItemIdSetUnused125 *		Set the item identifier to be UNUSED, with no storage.126 *		Beware of multiple evaluations of itemId!127 */128#define ItemIdSetUnused(itemId) \129( \130	(itemId)->lp_flags = LP_UNUSED, \131	(itemId)->lp_off = 0, \132	(itemId)->lp_len = 0 \133)134 135/*136 * ItemIdSetNormal137 *		Set the item identifier to be NORMAL, with the specified storage.138 *		Beware of multiple evaluations of itemId!139 */140#define ItemIdSetNormal(itemId, off, len) \141( \142	(itemId)->lp_flags = LP_NORMAL, \143	(itemId)->lp_off = (off), \144	(itemId)->lp_len = (len) \145)146 147/*148 * ItemIdSetRedirect149 *		Set the item identifier to be REDIRECT, with the specified link.150 *		Beware of multiple evaluations of itemId!151 */152#define ItemIdSetRedirect(itemId, link) \153( \154	(itemId)->lp_flags = LP_REDIRECT, \155	(itemId)->lp_off = (link), \156	(itemId)->lp_len = 0 \157)158 159/*160 * ItemIdSetDead161 *		Set the item identifier to be DEAD, with no storage.162 *		Beware of multiple evaluations of itemId!163 */164#define ItemIdSetDead(itemId) \165( \166	(itemId)->lp_flags = LP_DEAD, \167	(itemId)->lp_off = 0, \168	(itemId)->lp_len = 0 \169)170 171/*172 * ItemIdMarkDead173 *		Set the item identifier to be DEAD, keeping its existing storage.174 *175 * Note: in indexes, this is used as if it were a hint-bit mechanism;176 * we trust that multiple processors can do this in parallel and get177 * the same result.178 */179#define ItemIdMarkDead(itemId) \180( \181	(itemId)->lp_flags = LP_DEAD \182)183 184#endif							/* ITEMID_H */185