1#pragma ident "%Z%%M% %I% %E% SMI" 2 3/*- 4 * Copyright (c) 1990, 1993, 1994 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Mike Olson. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39#if defined(LIBC_SCCS) && !defined(lint) 40static char sccsid[] = "@(#)bt_search.c 8.9 (Berkeley) 10/26/95"; 41#endif /* LIBC_SCCS and not lint */ 42 43#include <sys/types.h> 44 45#include <stdio.h> 46 47#include "db-int.h" 48#include "btree.h" 49 50static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *)); 51static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *)); 52 53/* 54 * __bt_search -- 55 * Search a btree for a key. 56 * 57 * Parameters: 58 * t: tree to search 59 * key: key to find 60 * exactp: pointer to exact match flag 61 * 62 * Returns: 63 * The EPG for matching record, if any, or the EPG for the location 64 * of the key, if it were inserted into the tree, is entered into 65 * the bt_cur field of the tree. A pointer to the field is returned. 66 */ 67EPG * 68__bt_search(t, key, exactp) 69 BTREE *t; 70 const DBT *key; 71 int *exactp; 72{ 73 PAGE *h; 74 indx_t base, idx, lim; 75 db_pgno_t pg; 76 int cmp; 77 78 BT_CLR(t); 79 for (pg = P_ROOT;;) { 80 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 81 return (NULL); 82 83 /* Do a binary search on the current page. */ 84 t->bt_cur.page = h; 85 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 86 t->bt_cur.index = idx = base + (lim >> 1); 87 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 88 if (h->flags & P_BLEAF) { 89 *exactp = 1; 90 return (&t->bt_cur); 91 } 92 goto next; 93 } 94 if (cmp > 0) { 95 base = idx + 1; 96 --lim; 97 } 98 } 99 100 /* 101 * If it's a leaf page, we're almost done. If no duplicates 102 * are allowed, or we have an exact match, we're done. Else, 103 * it's possible that there were matching keys on this page, 104 * which later deleted, and we're on a page with no matches 105 * while there are matches on other pages. If at the start or 106 * end of a page, check the adjacent page. 107 */ 108 if (h->flags & P_BLEAF) { 109 if (!F_ISSET(t, B_NODUPS)) { 110 if (base == 0 && 111 h->prevpg != P_INVALID && 112 __bt_sprev(t, h, key, exactp)) 113 return (&t->bt_cur); 114 if (base == NEXTINDEX(h) && 115 h->nextpg != P_INVALID && 116 __bt_snext(t, h, key, exactp)) 117 return (&t->bt_cur); 118 } 119 *exactp = 0; 120 t->bt_cur.index = base; 121 return (&t->bt_cur); 122 } 123 124 /* 125 * No match found. Base is the smallest index greater than 126 * key and may be zero or a last + 1 index. If it's non-zero, 127 * decrement by one, and record the internal page which should 128 * be a parent page for the key. If a split later occurs, the 129 * inserted page will be to the right of the saved page. 130 */ 131 idx = base ? base - 1 : base; 132 133next: BT_PUSH(t, h->pgno, idx); 134 pg = GETBINTERNAL(h, idx)->pgno; 135 mpool_put(t->bt_mp, h, 0); 136 } 137} 138 139/* 140 * __bt_snext -- 141 * Check for an exact match after the key. 142 * 143 * Parameters: 144 * t: tree 145 * h: current page 146 * key: key 147 * exactp: pointer to exact match flag 148 * 149 * Returns: 150 * If an exact match found. 151 */ 152static int 153__bt_snext(t, h, key, exactp) 154 BTREE *t; 155 PAGE *h; 156 const DBT *key; 157 int *exactp; 158{ 159 BINTERNAL *bi; 160 EPG e; 161 EPGNO *parent; 162 indx_t idx; 163 db_pgno_t pgno; 164 int level; 165 166 /* 167 * Get the next page. The key is either an exact 168 * match, or not as good as the one we already have. 169 */ 170 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 171 return (0); 172 e.index = 0; 173 if (__bt_cmp(t, key, &e) != 0) { 174 mpool_put(t->bt_mp, e.page, 0); 175 return (0); 176 } 177 mpool_put(t->bt_mp, h, 0); 178 t->bt_cur = e; 179 *exactp = 1; 180 181 /* 182 * Adjust the stack for the movement. 183 * 184 * Move up the stack. 185 */ 186 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 187 /* Get the parent page. */ 188 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 189 return (0); 190 191 /* Move to the next index. */ 192 if (parent->index != NEXTINDEX(h) - 1) { 193 idx = parent->index + 1; 194 BT_PUSH(t, h->pgno, idx); 195 break; 196 } 197 mpool_put(t->bt_mp, h, 0); 198 } 199 200 /* Restore the stack. */ 201 while (level--) { 202 /* Push the next level down onto the stack. */ 203 bi = GETBINTERNAL(h, idx); 204 pgno = bi->pgno; 205 BT_PUSH(t, pgno, 0); 206 207 /* Lose the currently pinned page. */ 208 mpool_put(t->bt_mp, h, 0); 209 210 /* Get the next level down. */ 211 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 212 return (0); 213 idx = 0; 214 } 215 mpool_put(t->bt_mp, h, 0); 216 return (1); 217} 218 219/* 220 * __bt_sprev -- 221 * Check for an exact match before the key. 222 * 223 * Parameters: 224 * t: tree 225 * h: current page 226 * key: key 227 * exactp: pointer to exact match flag 228 * 229 * Returns: 230 * If an exact match found. 231 */ 232static int 233__bt_sprev(t, h, key, exactp) 234 BTREE *t; 235 PAGE *h; 236 const DBT *key; 237 int *exactp; 238{ 239 BINTERNAL *bi; 240 EPG e; 241 EPGNO *parent; 242 indx_t idx; 243 db_pgno_t pgno; 244 int level; 245 246 /* 247 * Get the previous page. The key is either an exact 248 * match, or not as good as the one we already have. 249 */ 250 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 251 return (0); 252 e.index = NEXTINDEX(e.page) - 1; 253 if (__bt_cmp(t, key, &e) != 0) { 254 mpool_put(t->bt_mp, e.page, 0); 255 return (0); 256 } 257 258 mpool_put(t->bt_mp, h, 0); 259 t->bt_cur = e; 260 *exactp = 1; 261 262 /* 263 * Adjust the stack for the movement. 264 * 265 * Move up the stack. 266 */ 267 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 268 /* Get the parent page. */ 269 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 270 return (1); 271 272 /* Move to the next index. */ 273 if (parent->index != 0) { 274 idx = parent->index - 1; 275 BT_PUSH(t, h->pgno, idx); 276 break; 277 } 278 mpool_put(t->bt_mp, h, 0); 279 } 280 281 /* Restore the stack. */ 282 while (level--) { 283 /* Push the next level down onto the stack. */ 284 bi = GETBINTERNAL(h, idx); 285 pgno = bi->pgno; 286 287 /* Lose the currently pinned page. */ 288 mpool_put(t->bt_mp, h, 0); 289 290 /* Get the next level down. */ 291 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 292 return (1); 293 294 idx = NEXTINDEX(h) - 1; 295 BT_PUSH(t, pgno, idx); 296 } 297 mpool_put(t->bt_mp, h, 0); 298 return (1); 299} 300