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-rw-r--r--db/btree/bt_delete.c657
1 files changed, 657 insertions, 0 deletions
diff --git a/db/btree/bt_delete.c b/db/btree/bt_delete.c
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+++ b/db/btree/bt_delete.c
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+/*-
+ * 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);
+}
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