diff options
Diffstat (limited to 'db/btree/bt_delete.c')
| -rw-r--r-- | db/btree/bt_delete.c | 657 |
1 files changed, 657 insertions, 0 deletions
diff --git a/db/btree/bt_delete.c b/db/btree/bt_delete.c new file mode 100644 index 0000000000..ece1ab656e --- /dev/null +++ b/db/btree/bt_delete.c @@ -0,0 +1,657 @@ +/*- + * Copyright (c) 1990, 1993, 1994 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Mike Olson. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#if defined(LIBC_SCCS) && !defined(lint) +static char sccsid[] = "@(#)bt_delete.c 8.13 (Berkeley) 7/28/94"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <errno.h> +#include <stdio.h> +#include <string.h> + +#include <db.h> +#include "btree.h" + +static int __bt_bdelete __P((BTREE *, const DBT *)); +static int __bt_curdel __P((BTREE *, const DBT *, PAGE *, u_int)); +static int __bt_pdelete __P((BTREE *, PAGE *)); +static int __bt_relink __P((BTREE *, PAGE *)); +static int __bt_stkacq __P((BTREE *, PAGE **, CURSOR *)); + +/* + * __bt_delete + * Delete the item(s) referenced by a key. + * + * Return RET_SPECIAL if the key is not found. + */ +int +__bt_delete(dbp, key, flags) + const DB *dbp; + const DBT *key; + u_int flags; +{ + BTREE *t; + CURSOR *c; + PAGE *h; + int status; + + t = dbp->internal; + + /* Toss any page pinned across calls. */ + if (t->bt_pinned != NULL) { + mpool_put(t->bt_mp, t->bt_pinned, 0); + t->bt_pinned = NULL; + } + + /* Check for change to a read-only tree. */ + if (F_ISSET(t, B_RDONLY)) { + errno = EPERM; + return (RET_ERROR); + } + + switch (flags) { + case 0: + status = __bt_bdelete(t, key); + break; + case R_CURSOR: + /* + * If flags is R_CURSOR, delete the cursor. Must already + * have started a scan and not have already deleted it. + */ + c = &t->bt_cursor; + if (F_ISSET(c, CURS_INIT)) { + if (F_ISSET(c, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE)) + return (RET_SPECIAL); + if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL) + return (RET_ERROR); + + /* + * If the page is about to be emptied, we'll need to + * delete it, which means we have to acquire a stack. + */ + if (NEXTINDEX(h) == 1) + if (__bt_stkacq(t, &h, &t->bt_cursor)) + return (RET_ERROR); + + status = __bt_dleaf(t, NULL, h, c->pg.index); + + if (NEXTINDEX(h) == 0 && status == RET_SUCCESS) { + if (__bt_pdelete(t, h)) + return (RET_ERROR); + } else + mpool_put(t->bt_mp, + h, status == RET_SUCCESS ? MPOOL_DIRTY : 0); + break; + } + /* FALLTHROUGH */ + default: + errno = EINVAL; + return (RET_ERROR); + } + if (status == RET_SUCCESS) + F_SET(t, B_MODIFIED); + return (status); +} + +/* + * __bt_stkacq -- + * Acquire a stack so we can delete a cursor entry. + * + * Parameters: + * t: tree + * hp: pointer to current, pinned PAGE pointer + * c: pointer to the cursor + * + * Returns: + * 0 on success, 1 on failure + */ +static int +__bt_stkacq(t, hp, c) + BTREE *t; + PAGE **hp; + CURSOR *c; +{ + BINTERNAL *bi; + EPG *e; + EPGNO *parent; + PAGE *h; + indx_t index; + pgno_t pgno; + recno_t nextpg, prevpg; + int exact, level; + + /* + * Find the first occurrence of the key in the tree. Toss the + * currently locked page so we don't hit an already-locked page. + */ + h = *hp; + mpool_put(t->bt_mp, h, 0); + if ((e = __bt_search(t, &c->key, &exact)) == NULL) + return (1); + h = e->page; + + /* See if we got it in one shot. */ + if (h->pgno == c->pg.pgno) + goto ret; + + /* + * Move right, looking for the page. At each move we have to move + * up the stack until we don't have to move to the next page. If + * we have to change pages at an internal level, we have to fix the + * stack back up. + */ + while (h->pgno != c->pg.pgno) { + if ((nextpg = h->nextpg) == P_INVALID) + break; + mpool_put(t->bt_mp, h, 0); + + /* Move up the stack. */ + for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { + /* Get the parent page. */ + if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) + return (1); + + /* Move to the next index. */ + if (parent->index != NEXTINDEX(h) - 1) { + index = parent->index + 1; + BT_PUSH(t, h->pgno, index); + break; + } + mpool_put(t->bt_mp, h, 0); + } + + /* Restore the stack. */ + while (level--) { + /* Push the next level down onto the stack. */ + bi = GETBINTERNAL(h, index); + pgno = bi->pgno; + BT_PUSH(t, pgno, 0); + + /* Lose the currently pinned page. */ + mpool_put(t->bt_mp, h, 0); + + /* Get the next level down. */ + if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) + return (1); + index = 0; + } + mpool_put(t->bt_mp, h, 0); + if ((h = mpool_get(t->bt_mp, nextpg, 0)) == NULL) + return (1); + } + + if (h->pgno == c->pg.pgno) + goto ret; + + /* Reacquire the original stack. */ + mpool_put(t->bt_mp, h, 0); + if ((e = __bt_search(t, &c->key, &exact)) == NULL) + return (1); + h = e->page; + + /* + * Move left, looking for the page. At each move we have to move + * up the stack until we don't have to change pages to move to the + * next page. If we have to change pages at an internal level, we + * have to fix the stack back up. + */ + while (h->pgno != c->pg.pgno) { + if ((prevpg = h->prevpg) == P_INVALID) + break; + mpool_put(t->bt_mp, h, 0); + + /* Move up the stack. */ + for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { + /* Get the parent page. */ + if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) + return (1); + + /* Move to the next index. */ + if (parent->index != 0) { + index = parent->index - 1; + BT_PUSH(t, h->pgno, index); + break; + } + mpool_put(t->bt_mp, h, 0); + } + + /* Restore the stack. */ + while (level--) { + /* Push the next level down onto the stack. */ + bi = GETBINTERNAL(h, index); + pgno = bi->pgno; + + /* Lose the currently pinned page. */ + mpool_put(t->bt_mp, h, 0); + + /* Get the next level down. */ + if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) + return (1); + + index = NEXTINDEX(h) - 1; + BT_PUSH(t, pgno, index); + } + mpool_put(t->bt_mp, h, 0); + if ((h = mpool_get(t->bt_mp, prevpg, 0)) == NULL) + return (1); + } + + +ret: mpool_put(t->bt_mp, h, 0); + return ((*hp = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL); +} + +/* + * __bt_bdelete -- + * Delete all key/data pairs matching the specified key. + * + * Parameters: + * t: tree + * key: key to delete + * + * Returns: + * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found. + */ +static int +__bt_bdelete(t, key) + BTREE *t; + const DBT *key; +{ + EPG *e; + PAGE *h; + int deleted, exact, redo; + + deleted = 0; + + /* Find any matching record; __bt_search pins the page. */ +loop: if ((e = __bt_search(t, key, &exact)) == NULL) + return (deleted ? RET_SUCCESS : RET_ERROR); + if (!exact) { + mpool_put(t->bt_mp, e->page, 0); + return (deleted ? RET_SUCCESS : RET_SPECIAL); + } + + /* + * Delete forward, then delete backward, from the found key. If + * there are duplicates and we reach either side of the page, do + * the key search again, so that we get them all. + */ + redo = 0; + h = e->page; + do { + if (__bt_dleaf(t, key, h, e->index)) { + mpool_put(t->bt_mp, h, 0); + return (RET_ERROR); + } + if (F_ISSET(t, B_NODUPS)) { + if (NEXTINDEX(h) == 0) { + if (__bt_pdelete(t, h)) + return (RET_ERROR); + } else + mpool_put(t->bt_mp, h, MPOOL_DIRTY); + return (RET_SUCCESS); + } + deleted = 1; + } while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0); + + /* Check for right-hand edge of the page. */ + if (e->index == NEXTINDEX(h)) + redo = 1; + + /* Delete from the key to the beginning of the page. */ + while (e->index-- > 0) { + if (__bt_cmp(t, key, e) != 0) + break; + if (__bt_dleaf(t, key, h, e->index) == RET_ERROR) { + mpool_put(t->bt_mp, h, 0); + return (RET_ERROR); + } + if (e->index == 0) + redo = 1; + } + + /* Check for an empty page. */ + if (NEXTINDEX(h) == 0) { + if (__bt_pdelete(t, h)) + return (RET_ERROR); + goto loop; + } + + /* Put the page. */ + mpool_put(t->bt_mp, h, MPOOL_DIRTY); + + if (redo) + goto loop; + return (RET_SUCCESS); +} + +/* + * __bt_pdelete -- + * Delete a single page from the tree. + * + * Parameters: + * t: tree + * h: leaf page + * + * Returns: + * RET_SUCCESS, RET_ERROR. + * + * Side-effects: + * mpool_put's the page + */ +static int +__bt_pdelete(t, h) + BTREE *t; + PAGE *h; +{ + BINTERNAL *bi; + PAGE *pg; + EPGNO *parent; + indx_t cnt, index, *ip, offset; + u_int32_t nksize; + char *from; + + /* + * Walk the parent page stack -- a LIFO stack of the pages that were + * traversed when we searched for the page where the delete occurred. + * Each stack entry is a page number and a page index offset. The + * offset is for the page traversed on the search. We've just deleted + * a page, so we have to delete the key from the parent page. + * + * If the delete from the parent page makes it empty, this process may + * continue all the way up the tree. We stop if we reach the root page + * (which is never deleted, it's just not worth the effort) or if the + * delete does not empty the page. + */ + while ((parent = BT_POP(t)) != NULL) { + /* Get the parent page. */ + if ((pg = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) + return (RET_ERROR); + + index = parent->index; + bi = GETBINTERNAL(pg, index); + + /* Free any overflow pages. */ + if (bi->flags & P_BIGKEY && + __ovfl_delete(t, bi->bytes) == RET_ERROR) { + mpool_put(t->bt_mp, pg, 0); + return (RET_ERROR); + } + + /* + * Free the parent if it has only the one key and it's not the + * root page. If it's the rootpage, turn it back into an empty + * leaf page. + */ + if (NEXTINDEX(pg) == 1) + if (pg->pgno == P_ROOT) { + pg->lower = BTDATAOFF; + pg->upper = t->bt_psize; + pg->flags = P_BLEAF; + } else { + if (__bt_relink(t, pg) || __bt_free(t, pg)) + return (RET_ERROR); + continue; + } + else { + /* Pack remaining key items at the end of the page. */ + nksize = NBINTERNAL(bi->ksize); + from = (char *)pg + pg->upper; + memmove(from + nksize, from, (char *)bi - from); + pg->upper += nksize; + + /* Adjust indices' offsets, shift the indices down. */ + offset = pg->linp[index]; + for (cnt = index, ip = &pg->linp[0]; cnt--; ++ip) + if (ip[0] < offset) + ip[0] += nksize; + for (cnt = NEXTINDEX(pg) - index; --cnt; ++ip) + ip[0] = ip[1] < offset ? ip[1] + nksize : ip[1]; + pg->lower -= sizeof(indx_t); + } + + mpool_put(t->bt_mp, pg, MPOOL_DIRTY); + break; + } + + /* Free the leaf page, as long as it wasn't the root. */ + if (h->pgno == P_ROOT) { + mpool_put(t->bt_mp, h, MPOOL_DIRTY); + return (RET_SUCCESS); + } + return (__bt_relink(t, h) || __bt_free(t, h)); +} + +/* + * __bt_dleaf -- + * Delete a single record from a leaf page. + * + * Parameters: + * t: tree + * key: referenced key + * h: page + * index: index on page to delete + * + * Returns: + * RET_SUCCESS, RET_ERROR. + */ +int +__bt_dleaf(t, key, h, index) + BTREE *t; + const DBT *key; + PAGE *h; + u_int index; +{ + BLEAF *bl; + indx_t cnt, *ip, offset; + u_int32_t nbytes; + void *to; + char *from; + + /* If this record is referenced by the cursor, delete the cursor. */ + if (F_ISSET(&t->bt_cursor, CURS_INIT) && + !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) && + t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index == index && + __bt_curdel(t, key, h, index)) + return (RET_ERROR); + + /* If the entry uses overflow pages, make them available for reuse. */ + to = bl = GETBLEAF(h, index); + if (bl->flags & P_BIGKEY && __ovfl_delete(t, bl->bytes) == RET_ERROR) + return (RET_ERROR); + if (bl->flags & P_BIGDATA && + __ovfl_delete(t, bl->bytes + bl->ksize) == RET_ERROR) + return (RET_ERROR); + + /* Pack the remaining key/data items at the end of the page. */ + nbytes = NBLEAF(bl); + from = (char *)h + h->upper; + memmove(from + nbytes, from, (char *)to - from); + h->upper += nbytes; + + /* Adjust the indices' offsets, shift the indices down. */ + offset = h->linp[index]; + for (cnt = index, ip = &h->linp[0]; cnt--; ++ip) + if (ip[0] < offset) + ip[0] += nbytes; + for (cnt = NEXTINDEX(h) - index; --cnt; ++ip) + ip[0] = ip[1] < offset ? ip[1] + nbytes : ip[1]; + h->lower -= sizeof(indx_t); + + /* If the cursor is on this page, adjust it as necessary. */ + if (F_ISSET(&t->bt_cursor, CURS_INIT) && + !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) && + t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index > index) + --t->bt_cursor.pg.index; + + return (RET_SUCCESS); +} + +/* + * __bt_curdel -- + * Delete the cursor. + * + * Parameters: + * t: tree + * key: referenced key (or NULL) + * h: page + * index: index on page to delete + * + * Returns: + * RET_SUCCESS, RET_ERROR. + */ +static int +__bt_curdel(t, key, h, index) + BTREE *t; + const DBT *key; + PAGE *h; + u_int index; +{ + CURSOR *c; + EPG e; + PAGE *pg; + int curcopy, status; + + /* + * If there are duplicates, move forward or backward to one. + * Otherwise, copy the key into the cursor area. + */ + c = &t->bt_cursor; + F_CLR(c, CURS_AFTER | CURS_BEFORE | CURS_ACQUIRE); + + curcopy = 0; + if (!F_ISSET(t, B_NODUPS)) { + /* + * We're going to have to do comparisons. If we weren't + * provided a copy of the key, i.e. the user is deleting + * the current cursor position, get one. + */ + if (key == NULL) { + e.page = h; + e.index = index; + if ((status = __bt_ret(t, &e, + &c->key, &c->key, NULL, NULL, 1)) != RET_SUCCESS) + return (status); + curcopy = 1; + key = &c->key; + } + /* Check previous key, if not at the beginning of the page. */ + if (index > 0) { + e.page = h; + e.index = index - 1; + if (__bt_cmp(t, key, &e) == 0) { + F_SET(c, CURS_BEFORE); + goto dup2; + } + } + /* Check next key, if not at the end of the page. */ + if (index < NEXTINDEX(h) - 1) { + e.page = h; + e.index = index + 1; + if (__bt_cmp(t, key, &e) == 0) { + F_SET(c, CURS_AFTER); + goto dup2; + } + } + /* Check previous key if at the beginning of the page. */ + if (index == 0 && h->prevpg != P_INVALID) { + if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) + return (RET_ERROR); + e.page = pg; + e.index = NEXTINDEX(pg) - 1; + if (__bt_cmp(t, key, &e) == 0) { + F_SET(c, CURS_BEFORE); + goto dup1; + } + mpool_put(t->bt_mp, pg, 0); + } + /* Check next key if at the end of the page. */ + if (index == NEXTINDEX(h) - 1 && h->nextpg != P_INVALID) { + if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) + return (RET_ERROR); + e.page = pg; + e.index = 0; + if (__bt_cmp(t, key, &e) == 0) { + F_SET(c, CURS_AFTER); +dup1: mpool_put(t->bt_mp, pg, 0); +dup2: c->pg.pgno = e.page->pgno; + c->pg.index = e.index; + return (RET_SUCCESS); + } + mpool_put(t->bt_mp, pg, 0); + } + } + e.page = h; + e.index = index; + if (curcopy || (status = + __bt_ret(t, &e, &c->key, &c->key, NULL, NULL, 1)) == RET_SUCCESS) { + F_SET(c, CURS_ACQUIRE); + return (RET_SUCCESS); + } + return (status); +} + +/* + * __bt_relink -- + * Link around a deleted page. + * + * Parameters: + * t: tree + * h: page to be deleted + */ +static int +__bt_relink(t, h) + BTREE *t; + PAGE *h; +{ + PAGE *pg; + + if (h->nextpg != P_INVALID) { + if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) + return (RET_ERROR); + pg->prevpg = h->prevpg; + mpool_put(t->bt_mp, pg, MPOOL_DIRTY); + } + if (h->prevpg != P_INVALID) { + if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) + return (RET_ERROR); + pg->nextpg = h->nextpg; + mpool_put(t->bt_mp, pg, MPOOL_DIRTY); + } + return (0); +} |