1 /* $NetBSD: bt_search.c,v 1.19 2016/09/24 21:31:25 christos Exp $ */ 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if HAVE_NBTOOL_CONFIG_H 36 #include "nbtool_config.h" 37 #endif 38 39 #include <sys/cdefs.h> 40 __RCSID("$NetBSD: bt_search.c,v 1.19 2016/09/24 21:31:25 christos Exp $"); 41 42 #include "namespace.h" 43 #include <sys/types.h> 44 45 #include <assert.h> 46 #include <stdio.h> 47 48 #include <db.h> 49 #include "btree.h" 50 51 static int __bt_snext(BTREE *, PAGE *, const DBT *, int *); 52 static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *); 53 54 /* 55 * __bt_search -- 56 * Search a btree for a key. 57 * 58 * Parameters: 59 * t: tree to search 60 * key: key to find 61 * exactp: pointer to exact match flag 62 * 63 * Returns: 64 * The EPG for matching record, if any, or the EPG for the location 65 * of the key, if it were inserted into the tree, is entered into 66 * the bt_cur field of the tree. A pointer to the field is returned. 67 */ 68 EPG * 69 __bt_search(BTREE *t, const DBT *key, int *exactp) 70 { 71 PAGE *h; 72 indx_t base, idx, lim; 73 pgno_t pg; 74 int cmp; 75 76 BT_CLR(t); 77 for (pg = P_ROOT;;) { 78 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 79 return (NULL); 80 81 /* Do a binary search on the current page. */ 82 t->bt_cur.page = h; 83 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 84 t->bt_cur.index = idx = base + ((uint32_t)lim >> 1); 85 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 86 if (h->flags & P_BLEAF) { 87 *exactp = 1; 88 return (&t->bt_cur); 89 } 90 goto next; 91 } 92 if (cmp > 0) { 93 base = idx + 1; 94 --lim; 95 } 96 } 97 98 /* 99 * If it's a leaf page, we're almost done. If no duplicates 100 * are allowed, or we have an exact match, we're done. Else, 101 * it's possible that there were matching keys on this page, 102 * which later deleted, and we're on a page with no matches 103 * while there are matches on other pages. If at the start or 104 * end of a page, check the adjacent page. 105 */ 106 if (h->flags & P_BLEAF) { 107 if (!F_ISSET(t, B_NODUPS)) { 108 if (base == 0 && 109 h->prevpg != P_INVALID && 110 __bt_sprev(t, h, key, exactp)) 111 return (&t->bt_cur); 112 if (base == NEXTINDEX(h) && 113 h->nextpg != P_INVALID && 114 __bt_snext(t, h, key, exactp)) 115 return (&t->bt_cur); 116 } 117 *exactp = 0; 118 t->bt_cur.index = base; 119 return (&t->bt_cur); 120 } 121 122 /* 123 * No match found. Base is the smallest index greater than 124 * key and may be zero or a last + 1 index. If it's non-zero, 125 * decrement by one, and record the internal page which should 126 * be a parent page for the key. If a split later occurs, the 127 * inserted page will be to the right of the saved page. 128 */ 129 idx = base ? base - 1 : base; 130 131 next: BT_PUSH(t, h->pgno, idx); 132 pg = GETBINTERNAL(h, idx)->pgno; 133 mpool_put(t->bt_mp, h, 0); 134 } 135 } 136 137 /* 138 * __bt_snext -- 139 * Check for an exact match after the key. 140 * 141 * Parameters: 142 * t: tree 143 * h: current page 144 * key: key 145 * exactp: pointer to exact match flag 146 * 147 * Returns: 148 * If an exact match found. 149 */ 150 static int 151 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) 152 { 153 BINTERNAL *bi; 154 EPG e; 155 EPGNO *parent; 156 indx_t idx = 0; 157 pgno_t pgno; 158 int level; 159 160 /* 161 * Get the next page. The key is either an exact 162 * match, or not as good as the one we already have. 163 */ 164 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 165 return 0; 166 e.index = 0; 167 if (__bt_cmp(t, key, &e) != 0) { 168 mpool_put(t->bt_mp, e.page, 0); 169 return 0; 170 } 171 mpool_put(t->bt_mp, h, 0); 172 t->bt_cur = e; 173 *exactp = 1; 174 175 /* 176 * Adjust the stack for the movement. 177 * 178 * Move up the stack. 179 */ 180 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 181 /* Get the parent page. */ 182 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 183 return 0; 184 185 /* Move to the next index. */ 186 if (parent->index != NEXTINDEX(h) - 1) { 187 idx = parent->index + 1; 188 BT_PUSH(t, h->pgno, idx); 189 break; 190 } 191 192 mpool_put(t->bt_mp, h, 0); 193 } 194 195 /* Restore the stack. */ 196 while (level--) { 197 /* Push the next level down onto the stack. */ 198 bi = GETBINTERNAL(h, idx); 199 pgno = bi->pgno; 200 BT_PUSH(t, pgno, 0); 201 202 /* Lose the currently pinned page. */ 203 mpool_put(t->bt_mp, h, 0); 204 205 /* Get the next level down. */ 206 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 207 return 0; 208 idx = 0; 209 } 210 mpool_put(t->bt_mp, h, 0); 211 return 1; 212 } 213 214 /* 215 * __bt_sprev -- 216 * Check for an exact match before the key. 217 * 218 * Parameters: 219 * t: tree 220 * h: current page 221 * key: key 222 * exactp: pointer to exact match flag 223 * 224 * Returns: 225 * If an exact match found. 226 */ 227 static int 228 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) 229 { 230 BINTERNAL *bi; 231 EPG e; 232 EPGNO *parent; 233 indx_t idx = 0; 234 pgno_t pgno; 235 int level; 236 237 /* 238 * Get the previous page. The key is either an exact 239 * match, or not as good as the one we already have. 240 */ 241 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 242 return 0; 243 e.index = NEXTINDEX(e.page) - 1; 244 if (__bt_cmp(t, key, &e) != 0) { 245 mpool_put(t->bt_mp, e.page, 0); 246 return 0; 247 } 248 249 mpool_put(t->bt_mp, h, 0); 250 t->bt_cur = e; 251 *exactp = 1; 252 253 /* 254 * Adjust the stack for the movement. 255 * 256 * Move up the stack. 257 */ 258 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 259 /* Get the parent page. */ 260 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 261 return 1; 262 263 /* Move to the next index. */ 264 if (parent->index != 0) { 265 idx = parent->index - 1; 266 BT_PUSH(t, h->pgno, idx); 267 break; 268 } 269 mpool_put(t->bt_mp, h, 0); 270 } 271 272 /* Restore the stack. */ 273 while (level--) { 274 /* Push the next level down onto the stack. */ 275 bi = GETBINTERNAL(h, idx); 276 pgno = bi->pgno; 277 278 /* Lose the currently pinned page. */ 279 mpool_put(t->bt_mp, h, 0); 280 281 /* Get the next level down. */ 282 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 283 return 1; 284 285 idx = NEXTINDEX(h) - 1; 286 BT_PUSH(t, pgno, idx); 287 } 288 mpool_put(t->bt_mp, h, 0); 289 return 1; 290 } 291
Indexes created Sat Sep 20 22:09:52 GMT 2025