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)
38static char sccsid[] = "@(#)bt_delete.c 8.13 (Berkeley) 7/28/94";
39#endif /* LIBC_SCCS and not lint */
40
41#include <sys/types.h>
42
43#include <errno.h>
44#include <stdio.h>
45#include <string.h>
46
47#include <db.h>
48#include "btree.h"
49
50static int __bt_bdelete __P((BTREE *, const DBT *));
51static int __bt_curdel __P((BTREE *, const DBT *, PAGE *, u_int));
52static int __bt_pdelete __P((BTREE *, PAGE *));
53static int __bt_relink __P((BTREE *, PAGE *));
54static int __bt_stkacq __P((BTREE *, PAGE **, CURSOR *));
55
56/*
57 * __bt_delete
58 * Delete the item(s) referenced by a key.
59 *
60 * Return RET_SPECIAL if the key is not found.
61 */
62int
63__bt_delete(dbp, key, flags)
64 const DB *dbp;
65 const DBT *key;
66 u_int flags;
67{
68 BTREE *t;
69 CURSOR *c;
70 PAGE *h;
71 int status;
72
73 t = dbp->internal;
74
75 /* Toss any page pinned across calls. */
76 if (t->bt_pinned != NULL) {
77 mpool_put(t->bt_mp, t->bt_pinned, 0);
78 t->bt_pinned = NULL;
79 }
80
81 /* Check for change to a read-only tree. */
82 if (F_ISSET(t, B_RDONLY)) {
83 errno = EPERM;
84 return (RET_ERROR);
85 }
86
87 switch (flags) {
88 case 0:
89 status = __bt_bdelete(t, key);
90 break;
91 case R_CURSOR:
92 /*
93 * If flags is R_CURSOR, delete the cursor. Must already
94 * have started a scan and not have already deleted it.
95 */
96 c = &t->bt_cursor;
97 if (F_ISSET(c, CURS_INIT)) {
98 if (F_ISSET(c, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE))
99 return (RET_SPECIAL);
100 if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL)
101 return (RET_ERROR);
102
103 /*
104 * If the page is about to be emptied, we'll need to
105 * delete it, which means we have to acquire a stack.
106 */
107 if (NEXTINDEX(h) == 1)
108 if (__bt_stkacq(t, &h, &t->bt_cursor))
109 return (RET_ERROR);
110
111 status = __bt_dleaf(t, NULL, h, c->pg.index);
112
113 if (NEXTINDEX(h) == 0 && status == RET_SUCCESS) {
114 if (__bt_pdelete(t, h))
115 return (RET_ERROR);
116 } else
117 mpool_put(t->bt_mp,
118 h, status == RET_SUCCESS ? MPOOL_DIRTY : 0);
119 break;
120 }
121 /* FALLTHROUGH */
122 default:
123 errno = EINVAL;
124 return (RET_ERROR);
125 }
126 if (status == RET_SUCCESS)
127 F_SET(t, B_MODIFIED);
128 return (status);
129}
130
131/*
132 * __bt_stkacq --
133 * Acquire a stack so we can delete a cursor entry.
134 *
135 * Parameters:
136 * t: tree
137 * hp: pointer to current, pinned PAGE pointer
138 * c: pointer to the cursor
139 *
140 * Returns:
141 * 0 on success, 1 on failure
142 */
143static int
144__bt_stkacq(t, hp, c)
145 BTREE *t;
146 PAGE **hp;
147 CURSOR *c;
148{
149 BINTERNAL *bi;
150 EPG *e;
151 EPGNO *parent;
152 PAGE *h;
153 indx_t index = 0;
154 pgno_t pgno;
155 recno_t nextpg, prevpg;
156 int exact, level;
157
158 /*
159 * Find the first occurrence of the key in the tree. Toss the
160 * currently locked page so we don't hit an already-locked page.
161 */
162 h = *hp;
163 mpool_put(t->bt_mp, h, 0);
164 if ((e = __bt_search(t, &c->key, &exact)) == NULL)
165 return (1);
166 h = e->page;
167
168 /* See if we got it in one shot. */
169 if (h->pgno == c->pg.pgno)
170 goto ret;
171
172 /*
173 * Move right, looking for the page. At each move we have to move
174 * up the stack until we don't have to move to the next page. If
175 * we have to change pages at an internal level, we have to fix the
176 * stack back up.
177 */
178 while (h->pgno != c->pg.pgno) {
179 if ((nextpg = h->nextpg) == P_INVALID)
180 break;
181 mpool_put(t->bt_mp, h, 0);
182
183 /* Move up the stack. */
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 (1);
188
189 /* Move to the next index. */
190 if (parent->index != NEXTINDEX(h) - 1) {
191 index = parent->index + 1;
192 BT_PUSH(t, h->pgno, index);
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, index);
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 (1);
211 index = 0;
212 }
213 mpool_put(t->bt_mp, h, 0);
214 if ((h = mpool_get(t->bt_mp, nextpg, 0)) == NULL)
215 return (1);
216 }
217
218 if (h->pgno == c->pg.pgno)
219 goto ret;
220
221 /* Reacquire the original stack. */
222 mpool_put(t->bt_mp, h, 0);
223 if ((e = __bt_search(t, &c->key, &exact)) == NULL)
224 return (1);
225 h = e->page;
226
227 /*
228 * Move left, looking for the page. At each move we have to move
229 * up the stack until we don't have to change pages to move to the
230 * next page. If we have to change pages at an internal level, we
231 * have to fix the stack back up.
232 */
233 while (h->pgno != c->pg.pgno) {
234 if ((prevpg = h->prevpg) == P_INVALID)
235 break;
236 mpool_put(t->bt_mp, h, 0);
237
238 /* Move up the stack. */
239 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
240 /* Get the parent page. */
241 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
242 return (1);
243
244 /* Move to the next index. */
245 if (parent->index != 0) {
246 index = parent->index - 1;
247 BT_PUSH(t, h->pgno, index);
248 break;
249 }
250 mpool_put(t->bt_mp, h, 0);
251 }
252
253 /* Restore the stack. */
254 while (level--) {
255 /* Push the next level down onto the stack. */
256 bi = GETBINTERNAL(h, index);
257 pgno = bi->pgno;
258
259 /* Lose the currently pinned page. */
260 mpool_put(t->bt_mp, h, 0);
261
262 /* Get the next level down. */
263 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
264 return (1);
265
266 index = NEXTINDEX(h) - 1;
267 BT_PUSH(t, pgno, index);
268 }
269 mpool_put(t->bt_mp, h, 0);
270 if ((h = mpool_get(t->bt_mp, prevpg, 0)) == NULL)
271 return (1);
272 }
273
274
275ret: mpool_put(t->bt_mp, h, 0);
276 return ((*hp = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL);
277}
278
279/*
280 * __bt_bdelete --
281 * Delete all key/data pairs matching the specified key.
282 *
283 * Parameters:
284 * t: tree
285 * key: key to delete
286 *
287 * Returns:
288 * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
289 */
290static int
291__bt_bdelete(t, key)
292 BTREE *t;
293 const DBT *key;
294{
295 EPG *e;
296 PAGE *h;
297 int deleted, exact, redo;
298
299 deleted = 0;
300
301 /* Find any matching record; __bt_search pins the page. */
302loop: if ((e = __bt_search(t, key, &exact)) == NULL)
303 return (deleted ? RET_SUCCESS : RET_ERROR);
304 if (!exact) {
305 mpool_put(t->bt_mp, e->page, 0);
306 return (deleted ? RET_SUCCESS : RET_SPECIAL);
307 }
308
309 /*
310 * Delete forward, then delete backward, from the found key. If
311 * there are duplicates and we reach either side of the page, do
312 * the key search again, so that we get them all.
313 */
314 redo = 0;
315 h = e->page;
316 do {
317 if (__bt_dleaf(t, key, h, e->index)) {
318 mpool_put(t->bt_mp, h, 0);
319 return (RET_ERROR);
320 }
321 if (F_ISSET(t, B_NODUPS)) {
322 if (NEXTINDEX(h) == 0) {
323 if (__bt_pdelete(t, h))
324 return (RET_ERROR);
325 } else
326 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
327 return (RET_SUCCESS);
328 }
329 deleted = 1;
330 } while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0);
331
332 /* Check for right-hand edge of the page. */
333 if (e->index == NEXTINDEX(h))
334 redo = 1;
335
336 /* Delete from the key to the beginning of the page. */
337 while (e->index-- > 0) {
338 if (__bt_cmp(t, key, e) != 0)
339 break;
340 if (__bt_dleaf(t, key, h, e->index) == RET_ERROR) {
341 mpool_put(t->bt_mp, h, 0);
342 return (RET_ERROR);
343 }
344 if (e->index == 0)
345 redo = 1;
346 }
347
348 /* Check for an empty page. */
349 if (NEXTINDEX(h) == 0) {
350 if (__bt_pdelete(t, h))
351 return (RET_ERROR);
352 goto loop;
353 }
354
355 /* Put the page. */
356 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
357
358 if (redo)
359 goto loop;
360 return (RET_SUCCESS);
361}
362
363/*
364 * __bt_pdelete --
365 * Delete a single page from the tree.
366 *
367 * Parameters:
368 * t: tree
369 * h: leaf page
370 *
371 * Returns:
372 * RET_SUCCESS, RET_ERROR.
373 *
374 * Side-effects:
375 * mpool_put's the page
376 */
377static int
378__bt_pdelete(t, h)
379 BTREE *t;
380 PAGE *h;
381{
382 BINTERNAL *bi;
383 PAGE *pg;
384 EPGNO *parent;
385 indx_t cnt, index, *ip, offset;
386 u_int32_t nksize;
387 char *from;
388
389 /*
390 * Walk the parent page stack -- a LIFO stack of the pages that were
391 * traversed when we searched for the page where the delete occurred.
392 * Each stack entry is a page number and a page index offset. The
393 * offset is for the page traversed on the search. We've just deleted
394 * a page, so we have to delete the key from the parent page.
395 *
396 * If the delete from the parent page makes it empty, this process may
397 * continue all the way up the tree. We stop if we reach the root page
398 * (which is never deleted, it's just not worth the effort) or if the
399 * delete does not empty the page.
400 */
401 while ((parent = BT_POP(t)) != NULL) {
402 /* Get the parent page. */
403 if ((pg = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
404 return (RET_ERROR);
405
406 index = parent->index;
407 bi = GETBINTERNAL(pg, index);
408
409 /* Free any overflow pages. */
410 if (bi->flags & P_BIGKEY &&
411 __ovfl_delete(t, bi->bytes) == RET_ERROR) {
412 mpool_put(t->bt_mp, pg, 0);
413 return (RET_ERROR);
414 }
415
416 /*
417 * Free the parent if it has only the one key and it's not the
418 * root page. If it's the rootpage, turn it back into an empty
419 * leaf page.
420 */
421 if (NEXTINDEX(pg) == 1)
422 if (pg->pgno == P_ROOT) {
423 pg->lower = BTDATAOFF;
424 pg->upper = t->bt_psize;
425 pg->flags = P_BLEAF;
426 } else {
427 if (__bt_relink(t, pg) || __bt_free(t, pg))
428 return (RET_ERROR);
429 continue;
430 }
431 else {
432 /* Pack remaining key items at the end of the page. */
433 nksize = NBINTERNAL(bi->ksize);
434 from = (char *)pg + pg->upper;
435 memmove(from + nksize, from, (char *)bi - from);
436 pg->upper += nksize;
437
438 /* Adjust indices' offsets, shift the indices down. */
439 offset = pg->linp[index];
440 for (cnt = index, ip = &pg->linp[0]; cnt--; ++ip)
441 if (ip[0] < offset)
442 ip[0] += nksize;
443 for (cnt = NEXTINDEX(pg) - index; --cnt; ++ip)
444 ip[0] = ip[1] < offset ? ip[1] + nksize : ip[1];
445 pg->lower -= sizeof(indx_t);
446 }
447
448 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
449 break;
450 }
451
452 /* Free the leaf page, as long as it wasn't the root. */
453 if (h->pgno == P_ROOT) {
454 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
455 return (RET_SUCCESS);
456 }
457 return (__bt_relink(t, h) || __bt_free(t, h));
458}
459
460/*
461 * __bt_dleaf --
462 * Delete a single record from a leaf page.
463 *
464 * Parameters:
465 * t: tree
466 * key: referenced key
467 * h: page
468 * index: index on page to delete
469 *
470 * Returns:
471 * RET_SUCCESS, RET_ERROR.
472 */
473int
474__bt_dleaf(t, key, h, index)
475 BTREE *t;
476 const DBT *key;
477 PAGE *h;
478 u_int index;
479{
480 BLEAF *bl;
481 indx_t cnt, *ip, offset;
482 u_int32_t nbytes;
483 void *to;
484 char *from;
485
486 /* If this record is referenced by the cursor, delete the cursor. */
487 if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
488 !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
489 t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index == index &&
490 __bt_curdel(t, key, h, index))
491 return (RET_ERROR);
492
493 /* If the entry uses overflow pages, make them available for reuse. */
494 to = bl = GETBLEAF(h, index);
495 if (bl->flags & P_BIGKEY && __ovfl_delete(t, bl->bytes) == RET_ERROR)
496 return (RET_ERROR);
497 if (bl->flags & P_BIGDATA &&
498 __ovfl_delete(t, bl->bytes + bl->ksize) == RET_ERROR)
499 return (RET_ERROR);
500
501 /* Pack the remaining key/data items at the end of the page. */
502 nbytes = NBLEAF(bl);
503 from = (char *)h + h->upper;
504 memmove(from + nbytes, from, (char *)to - from);
505 h->upper += nbytes;
506
507 /* Adjust the indices' offsets, shift the indices down. */
508 offset = h->linp[index];
509 for (cnt = index, ip = &h->linp[0]; cnt--; ++ip)
510 if (ip[0] < offset)
511 ip[0] += nbytes;
512 for (cnt = NEXTINDEX(h) - index; --cnt; ++ip)
513 ip[0] = ip[1] < offset ? ip[1] + nbytes : ip[1];
514 h->lower -= sizeof(indx_t);
515
516 /* If the cursor is on this page, adjust it as necessary. */
517 if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
518 !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
519 t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index > index)
520 --t->bt_cursor.pg.index;
521
522 return (RET_SUCCESS);
523}
524
525/*
526 * __bt_curdel --
527 * Delete the cursor.
528 *
529 * Parameters:
530 * t: tree
531 * key: referenced key (or NULL)
532 * h: page
533 * index: index on page to delete
534 *
535 * Returns:
536 * RET_SUCCESS, RET_ERROR.
537 */
538static int
539__bt_curdel(t, key, h, index)
540 BTREE *t;
541 const DBT *key;
542 PAGE *h;
543 u_int index;
544{
545 CURSOR *c;
546 EPG e;
547 PAGE *pg;
548 int curcopy, status;
549
550 /*
551 * If there are duplicates, move forward or backward to one.
552 * Otherwise, copy the key into the cursor area.
553 */
554 c = &t->bt_cursor;
555 F_CLR(c, CURS_AFTER | CURS_BEFORE | CURS_ACQUIRE);
556
557 curcopy = 0;
558 if (!F_ISSET(t, B_NODUPS)) {
559 /*
560 * We're going to have to do comparisons. If we weren't
561 * provided a copy of the key, i.e. the user is deleting
562 * the current cursor position, get one.
563 */
564 if (key == NULL) {
565 e.page = h;
566 e.index = index;
567 if ((status = __bt_ret(t, &e,
568 &c->key, &c->key, NULL, NULL, 1)) != RET_SUCCESS)
569 return (status);
570 curcopy = 1;
571 key = &c->key;
572 }
573 /* Check previous key, if not at the beginning of the page. */
574 if (index > 0) {
575 e.page = h;
576 e.index = index - 1;
577 if (__bt_cmp(t, key, &e) == 0) {
578 F_SET(c, CURS_BEFORE);
579 goto dup2;
580 }
581 }
582 /* Check next key, if not at the end of the page. */
583 if (index < NEXTINDEX(h) - 1) {
584 e.page = h;
585 e.index = index + 1;
586 if (__bt_cmp(t, key, &e) == 0) {
587 F_SET(c, CURS_AFTER);
588 goto dup2;
589 }
590 }
591 /* Check previous key if at the beginning of the page. */
592 if (index == 0 && h->prevpg != P_INVALID) {
593 if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
594 return (RET_ERROR);
595 e.page = pg;
596 e.index = NEXTINDEX(pg) - 1;
597 if (__bt_cmp(t, key, &e) == 0) {
598 F_SET(c, CURS_BEFORE);
599 goto dup1;
600 }
601 mpool_put(t->bt_mp, pg, 0);
602 }
603 /* Check next key if at the end of the page. */
604 if (index == NEXTINDEX(h) - 1 && h->nextpg != P_INVALID) {
605 if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
606 return (RET_ERROR);
607 e.page = pg;
608 e.index = 0;
609 if (__bt_cmp(t, key, &e) == 0) {
610 F_SET(c, CURS_AFTER);
611dup1: mpool_put(t->bt_mp, pg, 0);
612dup2: c->pg.pgno = e.page->pgno;
613 c->pg.index = e.index;
614 return (RET_SUCCESS);
615 }
616 mpool_put(t->bt_mp, pg, 0);
617 }
618 }
619 e.page = h;
620 e.index = index;
621 if (curcopy || (status =
622 __bt_ret(t, &e, &c->key, &c->key, NULL, NULL, 1)) == RET_SUCCESS) {
623 F_SET(c, CURS_ACQUIRE);
624 return (RET_SUCCESS);
625 }
626 return (status);
627}
628
629/*
630 * __bt_relink --
631 * Link around a deleted page.
632 *
633 * Parameters:
634 * t: tree
635 * h: page to be deleted
636 */
637static int
638__bt_relink(t, h)
639 BTREE *t;
640 PAGE *h;
641{
642 PAGE *pg;
643
644 if (h->nextpg != P_INVALID) {
645 if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
646 return (RET_ERROR);
647 pg->prevpg = h->prevpg;
648 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
649 }
650 if (h->prevpg != P_INVALID) {
651 if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
652 return (RET_ERROR);
653 pg->nextpg = h->nextpg;
654 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
655 }
656 return (0);
657}
658