postgresql/src/include/access/nbtree.h

/*-------------------------------------------------------------------------
 *
 * nbtree.h--
 *    header file for postgres btree access method implementation.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: nbtree.h,v 1.5 1997/01/10 09:36:33 vadim Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef	NBTREE_H
#define	NBTREE_H

#include <access/sdir.h>
#include <access/relscan.h>
#include <storage/itemid.h>
#include <storage/page.h>
#include <access/funcindex.h>
#include <access/itup.h>
#include <storage/buf.h>
#include <storage/itemptr.h>

/*
 *  BTPageOpaqueData -- At the end of every page, we store a pointer
 *  to both siblings in the tree.  See Lehman and Yao's paper for more
 *  info.  In addition, we need to know what sort of page this is
 *  (leaf or internal), and whether the page is available for reuse.
 *
 *  Lehman and Yao's algorithm requires a ``high key'' on every page.
 *  The high key on a page is guaranteed to be greater than or equal
 *  to any key that appears on this page.  Our insertion algorithm
 *  guarantees that we can use the initial least key on our right
 *  sibling as the high key.  We allocate space for the line pointer
 *  to the high key in the opaque data at the end of the page.
 *
 *  Rightmost pages in the tree have no high key.
 */

typedef struct BTPageOpaqueData {
    BlockNumber	btpo_prev;
    BlockNumber	btpo_next;
    uint16	btpo_flags;

#define BTP_LEAF	(1 << 0)
#define BTP_ROOT	(1 << 1)
#define BTP_FREE	(1 << 2)
#define BTP_META	(1 << 3)

} BTPageOpaqueData;

typedef BTPageOpaqueData	*BTPageOpaque;

/*
 *  ScanOpaqueData is used to remember which buffers we're currently
 *  examining in the scan.  We keep these buffers locked and pinned
 *  and recorded in the opaque entry of the scan in order to avoid
 *  doing a ReadBuffer() for every tuple in the index.  This avoids
 *  semop() calls, which are expensive.
 *
 *  And it's used to remember actual scankey info (we need in it
 *  if some scankeys evaled at runtime.
 */

typedef struct BTScanOpaqueData {
    Buffer	btso_curbuf;
    Buffer	btso_mrkbuf;
    uint16	qual_ok;		/* 0 for quals like key == 1 && key > 2 */
    uint16	numberOfKeys;		/* number of key attributes */
    ScanKey	keyData;		/* key descriptor */
} BTScanOpaqueData;

typedef BTScanOpaqueData	*BTScanOpaque;

/*
 *  BTItems are what we store in the btree.  Each item has an index
 *  tuple, including key and pointer values.  In addition, we must
 *  guarantee that all tuples in the index are unique, in order to
 *  satisfy some assumptions in Lehman and Yao.  The way that we do
 *  this is by generating a new OID for every insertion that we do in
 *  the tree.  This adds eight bytes to the size of btree index
 *  tuples.  Note that we do not use the OID as part of a composite
 *  key; the OID only serves as a unique identifier for a given index
 *  tuple (logical position within a page).
 */

typedef struct BTItemData {
    Oid				bti_oid;
    int32			bti_dummy;	/* padding to make bti_itup
						 * align at 8-byte boundary
						 */
    IndexTupleData		bti_itup;
} BTItemData;

typedef BTItemData	*BTItem;

/*
 *  BTStackData -- As we descend a tree, we push the (key, pointer)
 *  pairs from internal nodes onto a private stack.  If we split a
 *  leaf, we use this stack to walk back up the tree and insert data
 *  into parent nodes (and possibly to split them, too).  Lehman and
 *  Yao's update algorithm guarantees that under no circumstances can
 *  our private stack give us an irredeemably bad picture up the tree.
 *  Again, see the paper for details.
 */

typedef struct BTStackData {
    BlockNumber		bts_blkno;
    OffsetNumber	bts_offset;
    BTItem		bts_btitem;
    struct BTStackData	*bts_parent;
} BTStackData;

typedef BTStackData	*BTStack;

/*
 *  We need to be able to tell the difference between read and write
 *  requests for pages, in order to do locking correctly.
 */

#define	BT_READ		0
#define	BT_WRITE	1

/*
 *  Similarly, the difference between insertion and non-insertion binary
 *  searches on a given page makes a difference when we're descending the
 *  tree.
 */

#define BT_INSERTION	0
#define BT_DESCENT	1

/*
 *  In general, the btree code tries to localize its knowledge about
 *  page layout to a couple of routines.  However, we need a special
 *  value to indicate "no page number" in those places where we expect
 *  page numbers.
 */

#define P_NONE		0
#define	P_LEFTMOST(opaque)	((opaque)->btpo_prev == P_NONE)
#define	P_RIGHTMOST(opaque)	((opaque)->btpo_next == P_NONE)

#define	P_HIKEY		((OffsetNumber) 1)
#define	P_FIRSTKEY	((OffsetNumber) 2)

/*
 *  Strategy numbers -- ordering of these is <, <=, =, >=, > 
 */

#define BTLessStrategyNumber		1
#define BTLessEqualStrategyNumber	2
#define BTEqualStrategyNumber		3
#define BTGreaterEqualStrategyNumber	4
#define BTGreaterStrategyNumber		5
#define BTMaxStrategyNumber		5

/*
 *  When a new operator class is declared, we require that the user
 *  supply us with an amproc procedure for determining whether, for
 *  two keys a and b, a < b, a = b, or a > b.  This routine must
 *  return < 0, 0, > 0, respectively, in these three cases.  Since we
 *  only have one such proc in amproc, it's number 1.
 */

#define BTORDER_PROC	1


/*
 * prototypes for functions in nbtinsert.c
 */
extern InsertIndexResult _bt_doinsert(Relation rel, BTItem btitem,
				      bool index_is_unique, Relation heapRel);

				/* default is to allow duplicates */
extern bool _bt_itemcmp(Relation rel, Size keysz, BTItem item1, BTItem item2,
			StrategyNumber strat);

/*
 * prototypes for functions in nbtpage.c
 */
extern void _bt_metapinit(Relation rel);
extern void _bt_checkmeta(Relation rel);
extern Buffer _bt_getroot(Relation rel, int access);
extern Buffer _bt_getbuf(Relation rel, BlockNumber blkno, int access);
extern void _bt_relbuf(Relation rel, Buffer buf, int access);
extern void _bt_wrtbuf(Relation rel, Buffer buf);
extern void _bt_wrtnorelbuf(Relation rel, Buffer buf);
extern void _bt_pageinit(Page page, Size size);
extern void _bt_metaproot(Relation rel, BlockNumber rootbknum);
extern Buffer _bt_getstackbuf(Relation rel, BTStack stack, int access);
extern void _bt_setpagelock(Relation rel, BlockNumber blkno, int access);
extern void _bt_unsetpagelock(Relation rel, BlockNumber blkno, int access);
extern void _bt_pagedel(Relation rel, ItemPointer tid);

/*
 * prototypes for functions in nbtree.c
 */
extern bool BuildingBtree;	/* in nbtree.c */

extern void btbuild(Relation heap, Relation index, int natts,
	AttrNumber *attnum, IndexStrategy istrat, uint16 pcount,
	Datum *params, FuncIndexInfo *finfo, PredInfo *predInfo);
extern InsertIndexResult btinsert(Relation rel, Datum *datum, char *nulls,
				  ItemPointer ht_ctid, Relation heapRel);
extern char *btgettuple(IndexScanDesc scan, ScanDirection dir);
extern char *btbeginscan(Relation rel, bool fromEnd, uint16 keysz,
			 ScanKey scankey);

extern void btrescan(IndexScanDesc scan, bool fromEnd, ScanKey scankey);
extern void btmovescan(IndexScanDesc scan, Datum v);
extern void btendscan(IndexScanDesc scan);
extern void btmarkpos(IndexScanDesc scan);
extern void btrestrpos(IndexScanDesc scan);
extern void btdelete(Relation rel, ItemPointer tid);

/*
 * prototypes for functions in nbtscan.c
 */
extern void _bt_regscan(IndexScanDesc scan);
extern void _bt_dropscan(IndexScanDesc scan);
extern void _bt_adjscans(Relation rel, ItemPointer tid);
extern void _bt_scandel(IndexScanDesc scan, BlockNumber blkno,
			OffsetNumber offno);
extern bool _bt_scantouched(IndexScanDesc scan, BlockNumber blkno,
			    OffsetNumber offno);

/*
 * prototypes for functions in nbtsearch.c
 */
extern BTStack _bt_search(Relation rel, int keysz, ScanKey scankey,
			  Buffer *bufP);
extern Buffer _bt_moveright(Relation rel, Buffer buf, int keysz,
			    ScanKey scankey, int access);
extern bool _bt_skeycmp(Relation rel, Size keysz, ScanKey scankey,
			Page page, ItemId itemid, StrategyNumber strat);
extern OffsetNumber _bt_binsrch(Relation rel, Buffer buf, int keysz,
				ScanKey scankey, int srchtype);
extern RetrieveIndexResult _bt_next(IndexScanDesc scan, ScanDirection dir);
extern RetrieveIndexResult _bt_first(IndexScanDesc scan, ScanDirection dir);
extern bool _bt_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir);
extern int _bt_compare(Relation rel, TupleDesc itupdesc, Page page, int keysz, ScanKey scankey, OffsetNumber offnum);

/*
 * prototypes for functions in nbtstrat.c
 */
extern StrategyNumber _bt_getstrat(Relation rel, AttrNumber attno,
				   RegProcedure proc);
extern bool _bt_invokestrat(Relation rel, AttrNumber attno,
			    StrategyNumber strat, Datum left, Datum right);

/*
 * prototypes for functions in nbtutils.c
 */
extern ScanKey  _bt_mkscankey(Relation rel, IndexTuple itup);
extern void _bt_freeskey(ScanKey skey);
extern void _bt_freestack(BTStack stack);
extern void _bt_orderkeys(Relation relation, uint16 *numberOfKeys,
			  ScanKey key, uint16 *qual_ok);
extern bool _bt_checkqual(IndexScanDesc scan, IndexTuple itup);
extern BTItem _bt_formitem(IndexTuple itup);

/*
 * prototypes for functions in nbtsort.c
 */
extern void *_bt_spoolinit(Relation index, int ntapes);
extern void _bt_spooldestroy(void *spool);
extern void _bt_spool(Relation index, BTItem btitem, void *spool);
extern void _bt_upperbuild(Relation index, BlockNumber blk, int level);
extern void _bt_leafbuild(Relation index, void *spool);

#endif	/* NBTREE_H */