2 * Copyright (c) 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
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37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bt_delete.c 8.13 (Berkeley) 7/28/94";
39 #endif /* LIBC_SCCS and not lint */
41 #include <sys/types.h>
50 static int __bt_bdelete __P((BTREE *, const DBT *));
51 static int __bt_curdel __P((BTREE *, const DBT *, PAGE *, u_int));
52 static int __bt_pdelete __P((BTREE *, PAGE *));
53 static int __bt_relink __P((BTREE *, PAGE *));
54 static int __bt_stkacq __P((BTREE *, PAGE **, CURSOR *));
58 * Delete the item(s) referenced by a key.
60 * Return RET_SPECIAL if the key is not found.
63 __bt_delete(dbp, key, flags)
75 /* Toss any page pinned across calls. */
76 if (t->bt_pinned != NULL) {
77 mpool_put(t->bt_mp, t->bt_pinned, 0);
81 /* Check for change to a read-only tree. */
82 if (F_ISSET(t, B_RDONLY)) {
89 status = __bt_bdelete(t, key);
93 * If flags is R_CURSOR, delete the cursor. Must already
94 * have started a scan and not have already deleted it.
97 if (F_ISSET(c, CURS_INIT)) {
98 if (F_ISSET(c, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE))
100 if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL)
104 * If the page is about to be emptied, we'll need to
105 * delete it, which means we have to acquire a stack.
107 if (NEXTINDEX(h) == 1)
108 if (__bt_stkacq(t, &h, &t->bt_cursor))
111 status = __bt_dleaf(t, NULL, h, c->pg.index);
113 if (NEXTINDEX(h) == 0 && status == RET_SUCCESS) {
114 if (__bt_pdelete(t, h))
118 h, status == RET_SUCCESS ? MPOOL_DIRTY : 0);
126 if (status == RET_SUCCESS)
127 F_SET(t, B_MODIFIED);
133 * Acquire a stack so we can delete a cursor entry.
137 * hp: pointer to current, pinned PAGE pointer
138 * c: pointer to the cursor
141 * 0 on success, 1 on failure
144 __bt_stkacq(t, hp, c)
155 recno_t nextpg, prevpg;
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.
163 mpool_put(t->bt_mp, h, 0);
164 if ((e = __bt_search(t, &c->key, &exact)) == NULL)
168 /* See if we got it in one shot. */
169 if (h->pgno == c->pg.pgno)
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
178 while (h->pgno != c->pg.pgno) {
179 if ((nextpg = h->nextpg) == P_INVALID)
181 mpool_put(t->bt_mp, h, 0);
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)
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);
195 mpool_put(t->bt_mp, h, 0);
198 /* Restore the stack. */
200 /* Push the next level down onto the stack. */
201 bi = GETBINTERNAL(h, index);
205 /* Lose the currently pinned page. */
206 mpool_put(t->bt_mp, h, 0);
208 /* Get the next level down. */
209 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
213 mpool_put(t->bt_mp, h, 0);
214 if ((h = mpool_get(t->bt_mp, nextpg, 0)) == NULL)
218 if (h->pgno == c->pg.pgno)
221 /* Reacquire the original stack. */
222 mpool_put(t->bt_mp, h, 0);
223 if ((e = __bt_search(t, &c->key, &exact)) == NULL)
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.
233 while (h->pgno != c->pg.pgno) {
234 if ((prevpg = h->prevpg) == P_INVALID)
236 mpool_put(t->bt_mp, h, 0);
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)
244 /* Move to the next index. */
245 if (parent->index != 0) {
246 index = parent->index - 1;
247 BT_PUSH(t, h->pgno, index);
250 mpool_put(t->bt_mp, h, 0);
253 /* Restore the stack. */
255 /* Push the next level down onto the stack. */
256 bi = GETBINTERNAL(h, index);
259 /* Lose the currently pinned page. */
260 mpool_put(t->bt_mp, h, 0);
262 /* Get the next level down. */
263 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
266 index = NEXTINDEX(h) - 1;
267 BT_PUSH(t, pgno, index);
269 mpool_put(t->bt_mp, h, 0);
270 if ((h = mpool_get(t->bt_mp, prevpg, 0)) == NULL)
275 ret: mpool_put(t->bt_mp, h, 0);
276 return ((*hp = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL);
281 * Delete all key/data pairs matching the specified key.
288 * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
297 int deleted, exact, redo;
301 /* Find any matching record; __bt_search pins the page. */
302 loop: if ((e = __bt_search(t, key, &exact)) == NULL)
303 return (deleted ? RET_SUCCESS : RET_ERROR);
305 mpool_put(t->bt_mp, e->page, 0);
306 return (deleted ? RET_SUCCESS : RET_SPECIAL);
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.
317 if (__bt_dleaf(t, key, h, e->index)) {
318 mpool_put(t->bt_mp, h, 0);
321 if (F_ISSET(t, B_NODUPS)) {
322 if (NEXTINDEX(h) == 0) {
323 if (__bt_pdelete(t, h))
326 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
327 return (RET_SUCCESS);
330 } while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0);
332 /* Check for right-hand edge of the page. */
333 if (e->index == NEXTINDEX(h))
336 /* Delete from the key to the beginning of the page. */
337 while (e->index-- > 0) {
338 if (__bt_cmp(t, key, e) != 0)
340 if (__bt_dleaf(t, key, h, e->index) == RET_ERROR) {
341 mpool_put(t->bt_mp, h, 0);
348 /* Check for an empty page. */
349 if (NEXTINDEX(h) == 0) {
350 if (__bt_pdelete(t, h))
356 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
360 return (RET_SUCCESS);
365 * Delete a single page from the tree.
372 * RET_SUCCESS, RET_ERROR.
375 * mpool_put's the page
385 indx_t cnt, index, *ip, offset;
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.
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.
401 while ((parent = BT_POP(t)) != NULL) {
402 /* Get the parent page. */
403 if ((pg = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
406 index = parent->index;
407 bi = GETBINTERNAL(pg, index);
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);
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
421 if (NEXTINDEX(pg) == 1)
422 if (pg->pgno == P_ROOT) {
423 pg->lower = BTDATAOFF;
424 pg->upper = t->bt_psize;
427 if (__bt_relink(t, pg) || __bt_free(t, pg))
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);
438 /* Adjust indices' offsets, shift the indices down. */
439 offset = pg->linp[index];
440 for (cnt = index, ip = &pg->linp[0]; cnt--; ++ip)
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);
448 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
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);
457 return (__bt_relink(t, h) || __bt_free(t, h));
462 * Delete a single record from a leaf page.
466 * key: referenced key
468 * index: index on page to delete
471 * RET_SUCCESS, RET_ERROR.
474 __bt_dleaf(t, key, h, index)
481 indx_t cnt, *ip, offset;
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))
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)
497 if (bl->flags & P_BIGDATA &&
498 __ovfl_delete(t, bl->bytes + bl->ksize) == RET_ERROR)
501 /* Pack the remaining key/data items at the end of the page. */
503 from = (char *)h + h->upper;
504 memmove(from + nbytes, from, (char *)to - from);
507 /* Adjust the indices' offsets, shift the indices down. */
508 offset = h->linp[index];
509 for (cnt = index, ip = &h->linp[0]; cnt--; ++ip)
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);
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;
522 return (RET_SUCCESS);
531 * key: referenced key (or NULL)
533 * index: index on page to delete
536 * RET_SUCCESS, RET_ERROR.
539 __bt_curdel(t, key, h, index)
551 * If there are duplicates, move forward or backward to one.
552 * Otherwise, copy the key into the cursor area.
555 F_CLR(c, CURS_AFTER | CURS_BEFORE | CURS_ACQUIRE);
558 if (!F_ISSET(t, B_NODUPS)) {
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.
567 if ((status = __bt_ret(t, &e,
568 &c->key, &c->key, NULL, NULL, 1)) != RET_SUCCESS)
573 /* Check previous key, if not at the beginning of the page. */
577 if (__bt_cmp(t, key, &e) == 0) {
578 F_SET(c, CURS_BEFORE);
582 /* Check next key, if not at the end of the page. */
583 if (index < NEXTINDEX(h) - 1) {
586 if (__bt_cmp(t, key, &e) == 0) {
587 F_SET(c, CURS_AFTER);
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)
596 e.index = NEXTINDEX(pg) - 1;
597 if (__bt_cmp(t, key, &e) == 0) {
598 F_SET(c, CURS_BEFORE);
601 mpool_put(t->bt_mp, pg, 0);
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)
609 if (__bt_cmp(t, key, &e) == 0) {
610 F_SET(c, CURS_AFTER);
611 dup1: mpool_put(t->bt_mp, pg, 0);
612 dup2: c->pg.pgno = e.page->pgno;
613 c->pg.index = e.index;
614 return (RET_SUCCESS);
616 mpool_put(t->bt_mp, pg, 0);
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);
631 * Link around a deleted page.
635 * h: page to be deleted
644 if (h->nextpg != P_INVALID) {
645 if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
647 pg->prevpg = h->prevpg;
648 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
650 if (h->prevpg != P_INVALID) {
651 if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
653 pg->nextpg = h->nextpg;
654 mpool_put(t->bt_mp, pg, MPOOL_DIRTY);