1 /*-
2 * See the file LICENSE for redistribution information.
3 *
4 * Copyright (c) 1996, 1997, 1998
5 * Sleepycat Software. All rights reserved.
6 */
7 /*
8 * Copyright (c) 1990, 1993, 1994, 1995, 1996
9 * Keith Bostic. All rights reserved.
10 */
11 /*
12 * Copyright (c) 1990, 1993, 1994, 1995
13 * The Regents of the University of California. All rights reserved.
14 *
15 * This code is derived from software contributed to Berkeley by
16 * Mike Olson.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 * notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 * notice, this list of conditions and the following disclaimer in the
25 * documentation and/or other materials provided with the distribution.
26 * 3. All advertising materials mentioning features or use of this software
27 * must display the following acknowledgement:
28 * This product includes software developed by the University of
29 * California, Berkeley and its contributors.
30 * 4. Neither the name of the University nor the names of its contributors
31 * may be used to endorse or promote products derived from this software
32 * without specific prior written permission.
33 *
34 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
35 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
36 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
37 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
38 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
39 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
40 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
41 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
42 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
43 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 * SUCH DAMAGE.
45 */
46
47 #include "config.h"
48
49 #ifndef lint
50 static const char sccsid[] = "@(#)bt_search.c 10.25 (Sleepycat) 12/16/98";
51 #endif /* not lint */
52
53 #ifndef NO_SYSTEM_INCLUDES
54 #include <sys/types.h>
55
56 #include <errno.h>
57 #include <string.h>
58 #endif
59
60 #include "db_int.h"
61 #include "db_page.h"
62 #include "btree.h"
63
64 /*
65 * __bam_search --
66 * Search a btree for a key.
67 *
68 * PUBLIC: int __bam_search __P((DBC *,
69 * PUBLIC: const DBT *, u_int32_t, int, db_recno_t *, int *));
70 */
71 int
__bam_search(dbc,key,flags,stop,recnop,exactp)72 __bam_search(dbc, key, flags, stop, recnop, exactp)
73 DBC *dbc;
74 const DBT *key;
75 u_int32_t flags;
76 int stop, *exactp;
77 db_recno_t *recnop;
78 {
79 BTREE *t;
80 CURSOR *cp;
81 DB *dbp;
82 DB_LOCK lock;
83 PAGE *h;
84 db_indx_t base, i, indx, lim;
85 db_pgno_t pg;
86 db_recno_t recno;
87 int cmp, jump, ret, stack;
88
89 dbp = dbc->dbp;
90 cp = dbc->internal;
91 t = dbp->internal;
92 recno = 0;
93
94 BT_STK_CLR(cp);
95
96 /*
97 * There are several ways we search a btree tree. The flags argument
98 * specifies if we're acquiring read or write locks, if we position
99 * to the first or last item in a set of duplicates, if we return
100 * deleted items, and if we are locking pairs of pages. In addition,
101 * if we're modifying record numbers, we have to lock the entire tree
102 * regardless. See btree.h for more details.
103 *
104 * If write-locking pages, we need to know whether or not to acquire a
105 * write lock on a page before getting it. This depends on how deep it
106 * is in tree, which we don't know until we acquire the root page. So,
107 * if we need to lock the root page we may have to upgrade it later,
108 * because we won't get the correct lock initially.
109 *
110 * Retrieve the root page.
111 */
112 pg = PGNO_ROOT;
113 stack = F_ISSET(dbp, DB_BT_RECNUM) && LF_ISSET(S_STACK);
114 if ((ret = __bam_lget(dbc,
115 0, pg, stack ? DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
116 return (ret);
117 if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
118 (void)__BT_LPUT(dbc, lock);
119 return (ret);
120 }
121
122 /*
123 * Decide if we need to save this page; if we do, write lock it.
124 * We deliberately don't lock-couple on this call. If the tree
125 * is tiny, i.e., one page, and two threads are busily updating
126 * the root page, we're almost guaranteed deadlocks galore, as
127 * each one gets a read lock and then blocks the other's attempt
128 * for a write lock.
129 */
130 if (!stack &&
131 ((LF_ISSET(S_PARENT) && (u_int8_t)(stop + 1) >= h->level) ||
132 (LF_ISSET(S_WRITE) && h->level == LEAFLEVEL))) {
133 (void)memp_fput(dbp->mpf, h, 0);
134 (void)__BT_LPUT(dbc, lock);
135 if ((ret = __bam_lget(dbc, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
136 return (ret);
137 if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
138 (void)__BT_LPUT(dbc, lock);
139 return (ret);
140 }
141 stack = 1;
142 }
143
144 for (;;) {
145 /*
146 * Do a binary search on the current page. If we're searching
147 * a leaf page, we have to manipulate the indices in groups of
148 * two. If we're searching an internal page, they're an index
149 * per page item. If we find an exact match on a leaf page,
150 * we're done.
151 */
152 jump = TYPE(h) == P_LBTREE ? P_INDX : O_INDX;
153 for (base = 0,
154 lim = NUM_ENT(h) / (db_indx_t)jump; lim != 0; lim >>= 1) {
155 indx = base + ((lim >> 1) * jump);
156 if ((cmp =
157 __bam_cmp(dbp, key, h, indx, t->bt_compare)) == 0) {
158 if (TYPE(h) == P_LBTREE)
159 goto match;
160 goto next;
161 }
162 if (cmp > 0) {
163 base = indx + jump;
164 --lim;
165 }
166 }
167
168 /*
169 * No match found. Base is the smallest index greater than
170 * key and may be zero or a last + O_INDX index.
171 *
172 * If it's a leaf page, return base as the "found" value.
173 * Delete only deletes exact matches.
174 */
175 if (TYPE(h) == P_LBTREE) {
176 *exactp = 0;
177
178 if (LF_ISSET(S_EXACT))
179 goto notfound;
180
181 /*
182 * !!!
183 * Possibly returning a deleted record -- DB_SET_RANGE,
184 * DB_KEYFIRST and DB_KEYLAST don't require an exact
185 * match, and we don't want to walk multiple pages here
186 * to find an undeleted record. This is handled in the
187 * __bam_c_search() routine.
188 */
189 BT_STK_ENTER(cp, h, base, lock, ret);
190 return (ret);
191 }
192
193 /*
194 * If it's not a leaf page, record the internal page (which is
195 * a parent page for the key). Decrement the base by 1 if it's
196 * non-zero so that if a split later occurs, the inserted page
197 * will be to the right of the saved page.
198 */
199 indx = base > 0 ? base - O_INDX : base;
200
201 /*
202 * If we're trying to calculate the record number, sum up
203 * all the record numbers on this page up to the indx point.
204 */
205 if (recnop != NULL)
206 for (i = 0; i < indx; ++i)
207 recno += GET_BINTERNAL(h, i)->nrecs;
208
209 next: pg = GET_BINTERNAL(h, indx)->pgno;
210 if (stack) {
211 /* Return if this is the lowest page wanted. */
212 if (LF_ISSET(S_PARENT) && stop == h->level) {
213 BT_STK_ENTER(cp, h, indx, lock, ret);
214 return (ret);
215 }
216 BT_STK_PUSH(cp, h, indx, lock, ret);
217 if (ret != 0)
218 goto err;
219
220 if ((ret =
221 __bam_lget(dbc, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
222 goto err;
223 } else {
224 /*
225 * Decide if we want to return a reference to the next
226 * page in the return stack. If so, lock it and never
227 * unlock it.
228 */
229 if ((LF_ISSET(S_PARENT) &&
230 (u_int8_t)(stop + 1) >= (u_int8_t)(h->level - 1)) ||
231 (h->level - 1) == LEAFLEVEL)
232 stack = 1;
233
234 (void)memp_fput(dbp->mpf, h, 0);
235
236 if ((ret =
237 __bam_lget(dbc, 1, pg, stack && LF_ISSET(S_WRITE) ?
238 DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
239 goto err;
240 }
241 if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0)
242 goto err;
243 }
244 /* NOTREACHED */
245
246 match: *exactp = 1;
247
248 /*
249 * If we're trying to calculate the record number, add in the
250 * offset on this page and correct for the fact that records
251 * in the tree are 0-based.
252 */
253 if (recnop != NULL)
254 *recnop = recno + (indx / P_INDX) + 1;
255
256 /*
257 * If we got here, we know that we have a btree leaf page.
258 *
259 * If there are duplicates, go to the first/last one. This is
260 * safe because we know that we're not going to leave the page,
261 * all duplicate sets that are not on overflow pages exist on a
262 * single leaf page.
263 */
264 if (LF_ISSET(S_DUPLAST))
265 while (indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
266 h->inp[indx] == h->inp[indx + P_INDX])
267 indx += P_INDX;
268 else
269 while (indx > 0 &&
270 h->inp[indx] == h->inp[indx - P_INDX])
271 indx -= P_INDX;
272
273 /*
274 * Now check if we are allowed to return deleted items; if not
275 * find the next (or previous) non-deleted item.
276 */
277 if (LF_ISSET(S_DELNO)) {
278 if (LF_ISSET(S_DUPLAST))
279 while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
280 indx > 0 &&
281 h->inp[indx] == h->inp[indx - P_INDX])
282 indx -= P_INDX;
283 else
284 while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
285 indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
286 h->inp[indx] == h->inp[indx + P_INDX])
287 indx += P_INDX;
288
289 if (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type))
290 goto notfound;
291 }
292
293 BT_STK_ENTER(cp, h, indx, lock, ret);
294 return (ret);
295
296 notfound:
297 (void)memp_fput(dbp->mpf, h, 0);
298 (void)__BT_LPUT(dbc, lock);
299 ret = DB_NOTFOUND;
300
301 err: if (cp->csp > cp->sp) {
302 BT_STK_POP(cp);
303 __bam_stkrel(dbc, 0);
304 }
305 return (ret);
306 }
307
308 /*
309 * __bam_stkrel --
310 * Release all pages currently held in the stack.
311 *
312 * PUBLIC: int __bam_stkrel __P((DBC *, int));
313 */
314 int
__bam_stkrel(dbc,nolocks)315 __bam_stkrel(dbc, nolocks)
316 DBC *dbc;
317 int nolocks;
318 {
319 CURSOR *cp;
320 DB *dbp;
321 EPG *epg;
322
323 dbp = dbc->dbp;
324 cp = dbc->internal;
325
326 /* Release inner pages first. */
327 for (epg = cp->sp; epg <= cp->csp; ++epg) {
328 if (epg->page != NULL)
329 (void)memp_fput(dbp->mpf, epg->page, 0);
330 if (epg->lock != LOCK_INVALID)
331 if (nolocks)
332 (void)__BT_LPUT(dbc, epg->lock);
333 else
334 (void)__BT_TLPUT(dbc, epg->lock);
335 }
336
337 /* Clear the stack, all pages have been released. */
338 BT_STK_CLR(cp);
339
340 return (0);
341 }
342
343 /*
344 * __bam_stkgrow --
345 * Grow the stack.
346 *
347 * PUBLIC: int __bam_stkgrow __P((CURSOR *));
348 */
349 int
__bam_stkgrow(cp)350 __bam_stkgrow(cp)
351 CURSOR *cp;
352 {
353 EPG *p;
354 size_t entries;
355 int ret;
356
357 entries = cp->esp - cp->sp;
358
359 if ((ret = __os_calloc(entries * 2, sizeof(EPG), &p)) != 0)
360 return (ret);
361 memcpy(p, cp->sp, entries * sizeof(EPG));
362 if (cp->sp != cp->stack)
363 __os_free(cp->sp, entries * sizeof(EPG));
364 cp->sp = p;
365 cp->csp = p + entries;
366 cp->esp = p + entries * 2;
367 return (0);
368 }
369