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bt_search.c revision 1.9
      1  1.9  christos /*	$NetBSD: bt_search.c,v 1.9 1997/07/13 18:51:56 christos Exp $	*/
      2  1.7       cgd 
      3  1.1       cgd /*-
      4  1.8       cgd  * Copyright (c) 1990, 1993, 1994
      5  1.1       cgd  *	The Regents of the University of California.  All rights reserved.
      6  1.1       cgd  *
      7  1.1       cgd  * This code is derived from software contributed to Berkeley by
      8  1.1       cgd  * Mike Olson.
      9  1.1       cgd  *
     10  1.1       cgd  * Redistribution and use in source and binary forms, with or without
     11  1.1       cgd  * modification, are permitted provided that the following conditions
     12  1.1       cgd  * are met:
     13  1.1       cgd  * 1. Redistributions of source code must retain the above copyright
     14  1.1       cgd  *    notice, this list of conditions and the following disclaimer.
     15  1.1       cgd  * 2. Redistributions in binary form must reproduce the above copyright
     16  1.1       cgd  *    notice, this list of conditions and the following disclaimer in the
     17  1.1       cgd  *    documentation and/or other materials provided with the distribution.
     18  1.1       cgd  * 3. All advertising materials mentioning features or use of this software
     19  1.1       cgd  *    must display the following acknowledgement:
     20  1.1       cgd  *	This product includes software developed by the University of
     21  1.1       cgd  *	California, Berkeley and its contributors.
     22  1.1       cgd  * 4. Neither the name of the University nor the names of its contributors
     23  1.1       cgd  *    may be used to endorse or promote products derived from this software
     24  1.1       cgd  *    without specific prior written permission.
     25  1.1       cgd  *
     26  1.1       cgd  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  1.1       cgd  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  1.1       cgd  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  1.1       cgd  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  1.1       cgd  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  1.1       cgd  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  1.1       cgd  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  1.1       cgd  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  1.1       cgd  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  1.1       cgd  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  1.1       cgd  * SUCH DAMAGE.
     37  1.1       cgd  */
     38  1.1       cgd 
     39  1.9  christos #include <sys/cdefs.h>
     40  1.1       cgd #if defined(LIBC_SCCS) && !defined(lint)
     41  1.7       cgd #if 0
     42  1.8       cgd static char sccsid[] = "@(#)bt_search.c	8.8 (Berkeley) 7/31/94";
     43  1.7       cgd #else
     44  1.9  christos __RCSID("$NetBSD: bt_search.c,v 1.9 1997/07/13 18:51:56 christos Exp $");
     45  1.7       cgd #endif
     46  1.1       cgd #endif /* LIBC_SCCS and not lint */
     47  1.1       cgd 
     48  1.1       cgd #include <sys/types.h>
     49  1.1       cgd 
     50  1.1       cgd #include <stdio.h>
     51  1.1       cgd 
     52  1.1       cgd #include <db.h>
     53  1.1       cgd #include "btree.h"
     54  1.1       cgd 
     55  1.8       cgd static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *));
     56  1.8       cgd static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *));
     57  1.5       cgd 
     58  1.1       cgd /*
     59  1.8       cgd  * __bt_search --
     60  1.8       cgd  *	Search a btree for a key.
     61  1.1       cgd  *
     62  1.1       cgd  * Parameters:
     63  1.1       cgd  *	t:	tree to search
     64  1.1       cgd  *	key:	key to find
     65  1.1       cgd  *	exactp:	pointer to exact match flag
     66  1.1       cgd  *
     67  1.1       cgd  * Returns:
     68  1.4       cgd  *	The EPG for matching record, if any, or the EPG for the location
     69  1.4       cgd  *	of the key, if it were inserted into the tree, is entered into
     70  1.4       cgd  *	the bt_cur field of the tree.  A pointer to the field is returned.
     71  1.1       cgd  */
     72  1.1       cgd EPG *
     73  1.1       cgd __bt_search(t, key, exactp)
     74  1.1       cgd 	BTREE *t;
     75  1.1       cgd 	const DBT *key;
     76  1.1       cgd 	int *exactp;
     77  1.1       cgd {
     78  1.6       cgd 	PAGE *h;
     79  1.6       cgd 	indx_t base, index, lim;
     80  1.1       cgd 	pgno_t pg;
     81  1.6       cgd 	int cmp;
     82  1.1       cgd 
     83  1.1       cgd 	BT_CLR(t);
     84  1.1       cgd 	for (pg = P_ROOT;;) {
     85  1.1       cgd 		if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
     86  1.1       cgd 			return (NULL);
     87  1.1       cgd 
     88  1.1       cgd 		/* Do a binary search on the current page. */
     89  1.4       cgd 		t->bt_cur.page = h;
     90  1.1       cgd 		for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
     91  1.4       cgd 			t->bt_cur.index = index = base + (lim >> 1);
     92  1.4       cgd 			if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
     93  1.1       cgd 				if (h->flags & P_BLEAF) {
     94  1.1       cgd 					*exactp = 1;
     95  1.4       cgd 					return (&t->bt_cur);
     96  1.1       cgd 				}
     97  1.1       cgd 				goto next;
     98  1.1       cgd 			}
     99  1.1       cgd 			if (cmp > 0) {
    100  1.1       cgd 				base = index + 1;
    101  1.1       cgd 				--lim;
    102  1.1       cgd 			}
    103  1.1       cgd 		}
    104  1.1       cgd 
    105  1.5       cgd 		/*
    106  1.8       cgd 		 * If it's a leaf page, we're almost done.  If no duplicates
    107  1.8       cgd 		 * are allowed, or we have an exact match, we're done.  Else,
    108  1.8       cgd 		 * it's possible that there were matching keys on this page,
    109  1.8       cgd 		 * which later deleted, and we're on a page with no matches
    110  1.8       cgd 		 * while there are matches on other pages.  If at the start or
    111  1.8       cgd 		 * end of a page, check the adjacent page.
    112  1.5       cgd 		 */
    113  1.1       cgd 		if (h->flags & P_BLEAF) {
    114  1.8       cgd 			if (!F_ISSET(t, B_NODUPS)) {
    115  1.5       cgd 				if (base == 0 &&
    116  1.8       cgd 				    h->prevpg != P_INVALID &&
    117  1.8       cgd 				    __bt_sprev(t, h, key, exactp))
    118  1.5       cgd 					return (&t->bt_cur);
    119  1.5       cgd 				if (base == NEXTINDEX(h) &&
    120  1.8       cgd 				    h->nextpg != P_INVALID &&
    121  1.8       cgd 				    __bt_snext(t, h, key, exactp))
    122  1.5       cgd 					return (&t->bt_cur);
    123  1.5       cgd 			}
    124  1.8       cgd 			*exactp = 0;
    125  1.8       cgd 			t->bt_cur.index = base;
    126  1.4       cgd 			return (&t->bt_cur);
    127  1.1       cgd 		}
    128  1.1       cgd 
    129  1.1       cgd 		/*
    130  1.1       cgd 		 * No match found.  Base is the smallest index greater than
    131  1.1       cgd 		 * key and may be zero or a last + 1 index.  If it's non-zero,
    132  1.1       cgd 		 * decrement by one, and record the internal page which should
    133  1.1       cgd 		 * be a parent page for the key.  If a split later occurs, the
    134  1.1       cgd 		 * inserted page will be to the right of the saved page.
    135  1.1       cgd 		 */
    136  1.1       cgd 		index = base ? base - 1 : base;
    137  1.1       cgd 
    138  1.8       cgd next:		BT_PUSH(t, h->pgno, index);
    139  1.1       cgd 		pg = GETBINTERNAL(h, index)->pgno;
    140  1.1       cgd 		mpool_put(t->bt_mp, h, 0);
    141  1.1       cgd 	}
    142  1.5       cgd }
    143  1.5       cgd 
    144  1.5       cgd /*
    145  1.8       cgd  * __bt_snext --
    146  1.8       cgd  *	Check for an exact match after the key.
    147  1.5       cgd  *
    148  1.5       cgd  * Parameters:
    149  1.8       cgd  *	t:	tree
    150  1.8       cgd  *	h:	current page
    151  1.8       cgd  *	key:	key
    152  1.5       cgd  *	exactp:	pointer to exact match flag
    153  1.5       cgd  *
    154  1.5       cgd  * Returns:
    155  1.5       cgd  *	If an exact match found.
    156  1.5       cgd  */
    157  1.5       cgd static int
    158  1.8       cgd __bt_snext(t, h, key, exactp)
    159  1.5       cgd 	BTREE *t;
    160  1.5       cgd 	PAGE *h;
    161  1.5       cgd 	const DBT *key;
    162  1.5       cgd 	int *exactp;
    163  1.5       cgd {
    164  1.5       cgd 	EPG e;
    165  1.5       cgd 
    166  1.5       cgd 	/*
    167  1.8       cgd 	 * Get the next page.  The key is either an exact
    168  1.8       cgd 	 * match, or not as good as the one we already have.
    169  1.5       cgd 	 */
    170  1.8       cgd 	if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
    171  1.8       cgd 		return (0);
    172  1.8       cgd 	e.index = 0;
    173  1.8       cgd 	if (__bt_cmp(t, key, &e) == 0) {
    174  1.8       cgd 		mpool_put(t->bt_mp, h, 0);
    175  1.8       cgd 		t->bt_cur = e;
    176  1.8       cgd 		*exactp = 1;
    177  1.8       cgd 		return (1);
    178  1.5       cgd 	}
    179  1.8       cgd 	mpool_put(t->bt_mp, e.page, 0);
    180  1.5       cgd 	return (0);
    181  1.5       cgd }
    182  1.5       cgd 
    183  1.5       cgd /*
    184  1.8       cgd  * __bt_sprev --
    185  1.8       cgd  *	Check for an exact match before the key.
    186  1.5       cgd  *
    187  1.5       cgd  * Parameters:
    188  1.8       cgd  *	t:	tree
    189  1.8       cgd  *	h:	current page
    190  1.8       cgd  *	key:	key
    191  1.5       cgd  *	exactp:	pointer to exact match flag
    192  1.5       cgd  *
    193  1.5       cgd  * Returns:
    194  1.5       cgd  *	If an exact match found.
    195  1.5       cgd  */
    196  1.5       cgd static int
    197  1.8       cgd __bt_sprev(t, h, key, exactp)
    198  1.5       cgd 	BTREE *t;
    199  1.5       cgd 	PAGE *h;
    200  1.5       cgd 	const DBT *key;
    201  1.5       cgd 	int *exactp;
    202  1.5       cgd {
    203  1.5       cgd 	EPG e;
    204  1.5       cgd 
    205  1.5       cgd 	/*
    206  1.8       cgd 	 * Get the previous page.  The key is either an exact
    207  1.8       cgd 	 * match, or not as good as the one we already have.
    208  1.5       cgd 	 */
    209  1.8       cgd 	if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
    210  1.8       cgd 		return (0);
    211  1.8       cgd 	e.index = NEXTINDEX(e.page) - 1;
    212  1.8       cgd 	if (__bt_cmp(t, key, &e) == 0) {
    213  1.8       cgd 		mpool_put(t->bt_mp, h, 0);
    214  1.8       cgd 		t->bt_cur = e;
    215  1.8       cgd 		*exactp = 1;
    216  1.8       cgd 		return (1);
    217  1.5       cgd 	}
    218  1.8       cgd 	mpool_put(t->bt_mp, e.page, 0);
    219  1.5       cgd 	return (0);
    220  1.1       cgd }
    221