lib/libc/db/btree/bt_delete.c

/*-
 * Copyright (c) 1990, 1993
 *      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 8.2 (Berkeley) 9/7/93";
#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 *));

/*
 * __BT_DELETE -- Delete the item(s) referenced by a key.
 *
 * Parameters:
 *      dbp:    pointer to access method
 *      key:    key to delete
 *      flags:  R_CURSOR if deleting what the cursor references
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
 */
int
__bt_delete(dbp, key, flags)
        const DB *dbp;
        const DBT *key;
        u_int flags;
{
        BTREE *t;
        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;
        }

        if (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 the record.  For
                 * the delete cursor bit to have been set requires that the
                 * scan be initialized, so no reason to check.
                 */
                if (!ISSET(t, B_SEQINIT))
                        goto einval;
                status = ISSET(t, B_DELCRSR) ?
                    RET_SPECIAL : __bt_crsrdel(t, &t->bt_bcursor);
                break;
        default:
einval:         errno = EINVAL;
                return (RET_ERROR);
        }
        if (status == RET_SUCCESS)
                SET(t, B_MODIFIED);
        return (status);
}

/*
 * BT_BDELETE -- Delete all key/data pairs matching the specified key.
 *
 * Parameters:
 *      tree:   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, save;
        PAGE *h;
        pgno_t cpgno, pg;
        indx_t cindex;
        int deleted, dirty1, dirty2, exact;

        /* Find any matching record; __bt_search pins the page. */
        if ((e = __bt_search(t, key, &exact)) == NULL)
                return (RET_ERROR);
        if (!exact) {
                mpool_put(t->bt_mp, e->page, 0);
                return (RET_SPECIAL);
        }

        /*
         * Delete forward, then delete backward, from the found key.  The
         * ordering is so that the deletions don't mess up the page refs.
         * The first loop deletes the key from the original page, the second
         * unpins the original page.  In the first loop, dirty1 is set if
         * the original page is modified, and dirty2 is set if any subsequent
         * pages are modified.  In the second loop, dirty1 starts off set if
         * the original page has been modified, and is set if any subsequent
         * pages are modified.
         *
         * If find the key referenced by the cursor, don't delete it, just
         * flag it for future deletion.  The cursor page number is P_INVALID
         * unless the sequential scan is initialized, so no reason to check.
         * A special case is when the already deleted cursor record was the
         * only record found.  If so, then the delete opertion fails as no
         * records were deleted.
         *
         * Cycle in place in the current page until the current record doesn't
         * match the key or the page is empty.  If the latter, walk forward,
         * skipping empty pages and repeating until a record doesn't match
         * the key or the end of the tree is reached.
         */
        cpgno = t->bt_bcursor.pgno;
        cindex = t->bt_bcursor.index;
        save = *e;
        dirty1 = 0;
        for (h = e->page, deleted = 0;;) {
                dirty2 = 0;
                do {
                        if (h->pgno == cpgno && e->index == cindex) {
                                if (!ISSET(t, B_DELCRSR)) {
                                        SET(t, B_DELCRSR);
                                        deleted = 1;
                                }
                                ++e->index;
                        } else {
                                if (__bt_dleaf(t, h, e->index)) {
                                        if (h->pgno != save.page->pgno)
                                                mpool_put(t->bt_mp, h, dirty2);
                                        mpool_put(t->bt_mp, save.page, dirty1);
                                        return (RET_ERROR);
                                }
                                if (h->pgno == save.page->pgno)
                                        dirty1 = MPOOL_DIRTY;
                                else
                                        dirty2 = MPOOL_DIRTY;
                                deleted = 1;
                        }
                } while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0);

                /*
                 * Quit if didn't find a match, no next page, or first key on
                 * the next page doesn't match.  Don't unpin the original page
                 * unless an error occurs.
                 */
                if (e->index < NEXTINDEX(h))
                        break;
                for (;;) {
                        if ((pg = h->nextpg) == P_INVALID)
                                goto done1;
                        if (h->pgno != save.page->pgno)
                                mpool_put(t->bt_mp, h, dirty2);
                        if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) {
                                mpool_put(t->bt_mp, save.page, dirty1);
                                return (RET_ERROR);
                        }
                        if (NEXTINDEX(h) != 0) {
                                e->page = h;
                                e->index = 0;
                                break;
                        }
                }

                if (__bt_cmp(t, key, e) != 0)
                        break;
        }

        /*
         * Reach here with the original page and the last page referenced
         * pinned (they may be the same).  Release it if not the original.
         */
done1:  if (h->pgno != save.page->pgno)
                mpool_put(t->bt_mp, h, dirty2);

        /*
         * Walk backwards from the record previous to the record returned by
         * __bt_search, skipping empty pages, until a record doesn't match
         * the key or reach the beginning of the tree.
         */
        *e = save;
        for (;;) {
                if (e->index)
                        --e->index;
                for (h = e->page; e->index; --e->index) {
                        if (__bt_cmp(t, key, e) != 0)
                                goto done2;
                        if (h->pgno == cpgno && e->index == cindex) {
                                if (!ISSET(t, B_DELCRSR)) {
                                        SET(t, B_DELCRSR);
                                        deleted = 1;
                                }
                        } else {
                                if (__bt_dleaf(t, h, e->index) == RET_ERROR) {
                                        mpool_put(t->bt_mp, h, dirty1);
                                        return (RET_ERROR);
                                }
                                if (h->pgno == save.page->pgno)
                                        dirty1 = MPOOL_DIRTY;
                                deleted = 1;
                        }
                }

                if ((pg = h->prevpg) == P_INVALID)
                        goto done2;
                mpool_put(t->bt_mp, h, dirty1);
                dirty1 = 0;
                if ((e->page = mpool_get(t->bt_mp, pg, 0)) == NULL)
                        return (RET_ERROR);
                e->index = NEXTINDEX(e->page);
        }

        /*
         * Reach here with the last page that was looked at pinned.  Release
         * it.
         */
done2:  mpool_put(t->bt_mp, h, dirty1);
        return (deleted ? RET_SUCCESS : RET_SPECIAL);
}

/*
 * __BT_DLEAF -- Delete a single record from a leaf page.
 *
 * Parameters:
 *      t:      tree
 *      index:  index on current page to delete
 *
 * Returns:
 *      RET_SUCCESS, RET_ERROR.
 */
int
__bt_dleaf(t, h, index)
        BTREE *t;
        PAGE *h;
        int index;
{
        register BLEAF *bl;
        register indx_t *ip, offset;
        register size_t nbytes;
        register int cnt;
        char *from;
        void *to;

        /*
         * Delete a record from a btree leaf page.  Internal records are never
         * deleted from internal pages, regardless of the records that caused
         * them to be added being deleted.  Pages made empty by deletion are
         * not reclaimed.  They are, however, made available for reuse.
         *
         * Pack the remaining entries at the end of the page, shift the indices
         * down, overwriting the deleted record and its index.  If the record
         * 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);
        nbytes = NBLEAF(bl);

        /*
         * Compress the key/data pairs.  Compress and adjust the [BR]LEAF
         * offsets.  Reset the headers.
         */
        from = (char *)h + h->upper;
        memmove(from + nbytes, from, (char *)to - from);
        h->upper += nbytes;

        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);
        return (RET_SUCCESS);
}