1 /*- 2 * Copyright (c) 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Mike Olson. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char sccsid[] = "@(#)bt_search.c 8.9 (Berkeley) 10/26/95"; 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include <sys/types.h> 42 43 #include <stdio.h> 44 45 #include "db-int.h" 46 #include "btree.h" 47 48 static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *)); 49 static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *)); 50 51 /* 52 * __bt_search -- 53 * Search a btree for a key. 54 * 55 * Parameters: 56 * t: tree to search 57 * key: key to find 58 * exactp: pointer to exact match flag 59 * 60 * Returns: 61 * The EPG for matching record, if any, or the EPG for the location 62 * of the key, if it were inserted into the tree, is entered into 63 * the bt_cur field of the tree. A pointer to the field is returned. 64 */ 65 EPG * 66 __bt_search(t, key, exactp) 67 BTREE *t; 68 const DBT *key; 69 int *exactp; 70 { 71 PAGE *h; 72 indx_t base, idx, lim; 73 db_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 + (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(t, h, key, exactp) 152 BTREE *t; 153 PAGE *h; 154 const DBT *key; 155 int *exactp; 156 { 157 BINTERNAL *bi; 158 EPG e; 159 EPGNO *parent; 160 indx_t idx; 161 db_pgno_t pgno; 162 int level; 163 164 /* 165 * Get the next page. The key is either an exact 166 * match, or not as good as the one we already have. 167 */ 168 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 169 return (0); 170 e.index = 0; 171 if (__bt_cmp(t, key, &e) != 0) { 172 mpool_put(t->bt_mp, e.page, 0); 173 return (0); 174 } 175 mpool_put(t->bt_mp, h, 0); 176 t->bt_cur = e; 177 *exactp = 1; 178 179 /* 180 * Adjust the stack for the movement. 181 * 182 * Move up the stack. 183 */ 184 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 185 /* Get the parent page. */ 186 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 187 return (0); 188 189 /* Move to the next index. */ 190 if (parent->index != NEXTINDEX(h) - 1) { 191 idx = parent->index + 1; 192 BT_PUSH(t, h->pgno, idx); 193 break; 194 } 195 mpool_put(t->bt_mp, h, 0); 196 } 197 198 /* Restore the stack. */ 199 while (level--) { 200 /* Push the next level down onto the stack. */ 201 bi = GETBINTERNAL(h, idx); 202 pgno = bi->pgno; 203 BT_PUSH(t, pgno, 0); 204 205 /* Lose the currently pinned page. */ 206 mpool_put(t->bt_mp, h, 0); 207 208 /* Get the next level down. */ 209 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 210 return (0); 211 idx = 0; 212 } 213 mpool_put(t->bt_mp, h, 0); 214 return (1); 215 } 216 217 /* 218 * __bt_sprev -- 219 * Check for an exact match before the key. 220 * 221 * Parameters: 222 * t: tree 223 * h: current page 224 * key: key 225 * exactp: pointer to exact match flag 226 * 227 * Returns: 228 * If an exact match found. 229 */ 230 static int 231 __bt_sprev(t, h, key, exactp) 232 BTREE *t; 233 PAGE *h; 234 const DBT *key; 235 int *exactp; 236 { 237 BINTERNAL *bi; 238 EPG e; 239 EPGNO *parent; 240 indx_t idx; 241 db_pgno_t pgno; 242 int level; 243 244 /* 245 * Get the previous page. The key is either an exact 246 * match, or not as good as the one we already have. 247 */ 248 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 249 return (0); 250 e.index = NEXTINDEX(e.page) - 1; 251 if (__bt_cmp(t, key, &e) != 0) { 252 mpool_put(t->bt_mp, e.page, 0); 253 return (0); 254 } 255 256 mpool_put(t->bt_mp, h, 0); 257 t->bt_cur = e; 258 *exactp = 1; 259 260 /* 261 * Adjust the stack for the movement. 262 * 263 * Move up the stack. 264 */ 265 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { 266 /* Get the parent page. */ 267 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 268 return (1); 269 270 /* Move to the next index. */ 271 if (parent->index != 0) { 272 idx = parent->index - 1; 273 BT_PUSH(t, h->pgno, idx); 274 break; 275 } 276 mpool_put(t->bt_mp, h, 0); 277 } 278 279 /* Restore the stack. */ 280 while (level--) { 281 /* Push the next level down onto the stack. */ 282 bi = GETBINTERNAL(h, idx); 283 pgno = bi->pgno; 284 285 /* Lose the currently pinned page. */ 286 mpool_put(t->bt_mp, h, 0); 287 288 /* Get the next level down. */ 289 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) 290 return (1); 291 292 idx = NEXTINDEX(h) - 1; 293 BT_PUSH(t, pgno, idx); 294 } 295 mpool_put(t->bt_mp, h, 0); 296 return (1); 297 } 298