Update.

[glibc.git] / db2 / btree / bt_delete.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997
 *      Sleepycat Software.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995, 1996
 *      Keith Bostic.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995
 *      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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)bt_delete.c   10.18 (Sleepycat) 8/24/97";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <stdio.h>
#include <string.h>
#endif

#include "db_int.h"
#include "db_page.h"
#include "btree.h"

static int __bam_dpages __P((DB *, BTREE *));

/*
 * __bam_delete --
 *      Delete the items referenced by a key.
 *
 * PUBLIC: int __bam_delete __P((DB *, DB_TXN *, DBT *, int));
 */
int
__bam_delete(argdbp, txn, key, flags)
        DB *argdbp;
        DB_TXN *txn;
        DBT *key;
        int flags;
{
        BTREE *t;
        DB *dbp;
        PAGE *h;
        db_indx_t cnt, i, indx;
        int dpage, exact, ret, stack;

        DEBUG_LWRITE(argdbp, txn, "bam_delete", key, NULL, flags);

        stack = 0;

        /* Check for invalid flags. */
        if ((ret =
            __db_delchk(argdbp, flags, F_ISSET(argdbp, DB_AM_RDONLY))) != 0)
                return (ret);

        GETHANDLE(argdbp, txn, &dbp, ret);
        t = dbp->internal;

        /* Search the tree for the key; delete only deletes exact matches. */
        if ((ret = __bam_search(dbp, key, S_DELETE, 1, NULL, &exact)) != 0)
                goto err;
        stack = 1;
        h = t->bt_csp->page;
        indx = t->bt_csp->indx;

        /* Delete the key/data pair, including any duplicates. */
        for (cnt = 1, i = indx;; ++cnt)
                if ((i += P_INDX) >= NUM_ENT(h) || h->inp[i] != h->inp[indx])
                        break;
        for (; cnt > 0; --cnt, ++t->lstat.bt_deleted)
                if (__bam_ca_delete(dbp, h->pgno, indx, NULL) != 0) {
                        GET_BKEYDATA(h, indx + O_INDX)->deleted = 1;
                        indx += P_INDX;
                } else if ((ret = __bam_ditem(dbp, h, indx)) != 0 ||
                    (ret = __bam_ditem(dbp, h, indx)) != 0)
                        goto err;

        /* If we're using record numbers, update internal page record counts. */
        if (F_ISSET(dbp, DB_BT_RECNUM) && (ret = __bam_adjust(dbp, t, -1)) != 0)
                goto err;

        /* If the page is now empty, delete it. */
        dpage = NUM_ENT(h) == 0 && h->pgno != PGNO_ROOT;

        __bam_stkrel(dbp);
        stack = 0;

        ret = dpage ? __bam_dpage(dbp, key) : 0;

err:    if (stack)
                __bam_stkrel(dbp);
        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __ram_delete --
 *      Delete the items referenced by a key.
 *
 * PUBLIC: int __ram_delete __P((DB *, DB_TXN *, DBT *, int));
 */
int
__ram_delete(argdbp, txn, key, flags)
        DB *argdbp;
        DB_TXN *txn;
        DBT *key;
        int flags;
{
        BKEYDATA bk;
        BTREE *t;
        DB *dbp;
        DBT hdr, data;
        PAGE *h;
        db_indx_t indx;
        db_recno_t recno;
        int exact, ret, stack;

        stack = 0;

        /* Check for invalid flags. */
        if ((ret =
            __db_delchk(argdbp, flags, F_ISSET(argdbp, DB_AM_RDONLY))) != 0)
                return (ret);

        GETHANDLE(argdbp, txn, &dbp, ret);
        t = dbp->internal;

        /* Check the user's record number and fill in as necessary. */
        if ((ret = __ram_getno(argdbp, key, &recno, 0)) != 0)
                goto err;

        /* Search the tree for the key; delete only deletes exact matches. */
        if ((ret = __bam_rsearch(dbp, &recno, S_DELETE, 1, &exact)) != 0)
                goto err;
        if (!exact) {
                ret = DB_NOTFOUND;
                goto err;
        }

        h = t->bt_csp->page;
        indx = t->bt_csp->indx;
        stack = 1;

        /* If the record has already been deleted, we couldn't have found it. */
        if (GET_BKEYDATA(h, indx)->deleted) {
                ret = DB_KEYEMPTY;
                goto done;
        }

        /*
         * If we're not renumbering records, replace the record with a marker
         * and return.
         */
        if (!F_ISSET(dbp, DB_RE_RENUMBER)) {
                if ((ret = __bam_ditem(dbp, h, indx)) != 0)
                        goto err;

                bk.deleted = 1;
                bk.type = B_KEYDATA;
                bk.len = 0;
                memset(&hdr, 0, sizeof(hdr));
                hdr.data = &bk;
                hdr.size = SSZA(BKEYDATA, data);
                memset(&data, 0, sizeof(data));
                data.data = (char *) "";
                data.size = 0;
                if ((ret = __db_pitem(dbp,
                    h, indx, BKEYDATA_SIZE(0), &hdr, &data)) != 0)
                        goto err;

                ++t->lstat.bt_deleted;
                goto done;
        }

        /* Delete the item. */
        if ((ret = __bam_ditem(dbp, h, indx)) != 0)
                goto err;

        ++t->lstat.bt_deleted;
        if (t->bt_recno != NULL)
                F_SET(t->bt_recno, RECNO_MODIFIED);

        /* Adjust the counts. */
        __bam_adjust(dbp, t, -1);

        /* Adjust the cursors. */
        __ram_ca(dbp, recno, CA_DELETE);

        /*
         * If the page is now empty, delete it -- we have the whole tree
         * locked, so there are no preparations to make.  Else, release
         * the pages.
         */
        if (NUM_ENT(h) == 0 && h->pgno != PGNO_ROOT) {
                stack = 0;
                ret = __bam_dpages(dbp, t);
        }

done:
err:    if (stack)
                __bam_stkrel(dbp);

        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __bam_ditem --
 *      Delete one or more entries from a page.
 *
 * PUBLIC: int __bam_ditem __P((DB *, PAGE *, u_int32_t));
 */
int
__bam_ditem(dbp, h, indx)
        DB *dbp;
        PAGE *h;
        u_int32_t indx;
{
        BINTERNAL *bi;
        BKEYDATA *bk;
        BOVERFLOW *bo;
        u_int32_t nbytes;
        int ret;

        switch (TYPE(h)) {
        case P_IBTREE:
                bi = GET_BINTERNAL(h, indx);
                switch (bi->type) {
                case B_DUPLICATE:
                case B_OVERFLOW:
                        nbytes = BINTERNAL_SIZE(bi->len);
                        goto offpage;
                case B_KEYDATA:
                        nbytes = BKEYDATA_SIZE(bi->len);
                        break;
                default:
                        return (__db_pgfmt(dbp, h->pgno));
                }
                break;
        case P_IRECNO:
                nbytes = RINTERNAL_SIZE;
                break;
        case P_LBTREE:
                /*
                 * If it's a duplicate key, discard the index and don't touch
                 * the actual page item.  This works because no data item can
                 * have an index that matches any other index so even if the
                 * data item is in an index "slot", it won't match any other
                 * index.
                 */
                if (!(indx % 2)) {
                        if (indx > 0 && h->inp[indx] == h->inp[indx - P_INDX])
                                return (__bam_adjindx(dbp,
                                    h, indx, indx - P_INDX, 0));
                        if (indx < (u_int32_t)(NUM_ENT(h) - P_INDX) &&
                            h->inp[indx] == h->inp[indx + P_INDX])
                                return (__bam_adjindx(dbp,
                                    h, indx, indx + O_INDX, 0));
                }
                /* FALLTHROUGH */
        case P_LRECNO:
                bk = GET_BKEYDATA(h, indx);
                switch (bk->type) {
                case B_DUPLICATE:
                case B_OVERFLOW:
                        nbytes = BOVERFLOW_SIZE;

offpage:                /* Delete duplicate/offpage chains. */
                        bo = GET_BOVERFLOW(h, indx);
                        if (bo->type == B_DUPLICATE) {
                                if ((ret =
                                    __db_ddup(dbp, bo->pgno, __bam_free)) != 0)
                                        return (ret);
                        } else
                                if ((ret =
                                    __db_doff(dbp, bo->pgno, __bam_free)) != 0)
                                        return (ret);
                        break;
                case B_KEYDATA:
                        nbytes = BKEYDATA_SIZE(bk->len);
                        break;
                default:
                        return (__db_pgfmt(dbp, h->pgno));
                }
                break;
        default:
                return (__db_pgfmt(dbp, h->pgno));
        }

        /* Delete the item. */
        if ((ret = __db_ditem(dbp, h, indx, nbytes)) != 0)
                return (ret);

        /* Mark the page dirty. */
        return (memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY));
}

/*
 * __bam_adjindx --
 *      Adjust an index on the page.
 *
 * PUBLIC: int __bam_adjindx __P((DB *, PAGE *, u_int32_t, u_int32_t, int));
 */
int
__bam_adjindx(dbp, h, indx, indx_copy, is_insert)
        DB *dbp;
        PAGE *h;
        u_int32_t indx, indx_copy;
        int is_insert;
{
        db_indx_t copy;
        int ret;

        /* Log the change. */
        if (DB_LOGGING(dbp) &&
            (ret = __bam_adj_log(dbp->dbenv->lg_info, dbp->txn, &LSN(h),
            0, dbp->log_fileid, PGNO(h), &LSN(h), indx, indx_copy,
            (u_int32_t)is_insert)) != 0)
                return (ret);

        if (is_insert) {
                copy = h->inp[indx_copy];
                if (indx != NUM_ENT(h))
                        memmove(&h->inp[indx + O_INDX], &h->inp[indx],
                            sizeof(db_indx_t) * (NUM_ENT(h) - indx));
                h->inp[indx] = copy;
                ++NUM_ENT(h);
        } else {
                --NUM_ENT(h);
                if (indx != NUM_ENT(h))
                        memmove(&h->inp[indx], &h->inp[indx + O_INDX],
                            sizeof(db_indx_t) * (NUM_ENT(h) - indx));
        }

        /* Mark the page dirty. */
        ret = memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY);

        /* Adjust the cursors. */
        __bam_ca_di(dbp, h->pgno, indx, is_insert ? 1 : -1);
        return (0);
}

/*
 * __bam_dpage --
 *      Delete a page from the tree.
 *
 * PUBLIC: int __bam_dpage __P((DB *, const DBT *));
 */
int
__bam_dpage(dbp, key)
        DB *dbp;
        const DBT *key;
{
        BTREE *t;
        DB_LOCK lock;
        PAGE *h;
        db_pgno_t pgno;
        int exact, level, ret;

        ret = 0;
        t = dbp->internal;

        /*
         * The locking protocol is that we acquire locks by walking down the
         * tree, to avoid the obvious deadlocks.
         *
         * Call __bam_search to reacquire the empty leaf page, but this time
         * get both the leaf page and it's parent, locked.  Walk back up the
         * tree, until we have the top pair of pages that we want to delete.
         * Once we have the top page that we want to delete locked, lock the
         * underlying pages and check to make sure they're still empty.  If
         * they are, delete them.
         */
        for (level = LEAFLEVEL;; ++level) {
                /* Acquire a page and its parent, locked. */
                if ((ret =
                    __bam_search(dbp, key, S_WRPAIR, level, NULL, &exact)) != 0)
                        return (ret);

                /*
                 * If we reach the root or the page isn't going to be empty
                 * when we delete one record, quit.
                 */
                h = t->bt_csp[-1].page;
                if (h->pgno == PGNO_ROOT || NUM_ENT(h) != 1)
                        break;

                /* Release the two locked pages. */
                (void)memp_fput(dbp->mpf, t->bt_csp[-1].page, 0);
                (void)__BT_TLPUT(dbp, t->bt_csp[-1].lock);
                (void)memp_fput(dbp->mpf, t->bt_csp[0].page, 0);
                (void)__BT_TLPUT(dbp, t->bt_csp[0].lock);
        }

        /*
         * Leave the stack pointer one after the last entry, we may be about
         * to push more items on the stack.
         */
        ++t->bt_csp;

        /*
         * t->bt_csp[-2].page is the top page, which we're not going to delete,
         * and t->bt_csp[-1].page is the first page we are going to delete.
         *
         * Walk down the chain, acquiring the rest of the pages until we've
         * retrieved the leaf page.  If we find any pages that aren't going
         * to be emptied by the delete, someone else added something while we
         * were walking the tree, and we discontinue the delete.
         */
        for (h = t->bt_csp[-1].page;;) {
                if (ISLEAF(h)) {
                        if (NUM_ENT(h) != 0)
                                goto release;
                        break;
                } else
                        if (NUM_ENT(h) != 1)
                                goto release;

                /*
                 * Get the next page, write lock it and push it onto the stack.
                 * We know it's index 0, because it can only have one element.
                 */
                pgno = TYPE(h) == P_IBTREE ?
                    GET_BINTERNAL(h, 0)->pgno : GET_RINTERNAL(h, 0)->pgno;

                if ((ret = __bam_lget(dbp, 0, pgno, DB_LOCK_WRITE, &lock)) != 0)
                        goto release;
                if ((ret = __bam_pget(dbp, &h, &pgno, 0)) != 0)
                        goto release;
                BT_STK_PUSH(t, h, 0, lock, ret);
                if (ret != 0)
                        goto release;
        }

        BT_STK_POP(t);
        return (__bam_dpages(dbp, t));

release:
        /* Discard any locked pages and return. */
        BT_STK_POP(t);
        __bam_stkrel(dbp);
        return (ret);
}

/*
 * __bam_dpages --
 *      Delete a set of locked pages.
 */
static int
__bam_dpages(dbp, t)
        DB *dbp;
        BTREE *t;
{
        DBT a, b;
        DB_LOCK lock;
        EPG *epg;
        PAGE *h;
        db_pgno_t pgno;
        db_recno_t rcnt;
        int ret;

        rcnt = 0;                               /* XXX: Shut the compiler up. */
        epg = t->bt_sp;

        /*
         * !!!
         * There is an interesting deadlock situation here.  We have to relink
         * the leaf page chain around the leaf page being deleted.  Consider
         * a cursor walking through the leaf pages, that has the previous page
         * read-locked and is waiting on a lock for the page we're deleting.
         * It will deadlock here.  This is a problem, because if our process is
         * selected to resolve the deadlock, we'll leave an empty leaf page
         * that we can never again access by walking down the tree.  So, before
         * we unlink the subtree, we relink the leaf page chain.
         */
        if ((ret = __db_relink(dbp, t->bt_csp->page, NULL, 1)) != 0)
                goto release;

        /*
         * We have the entire stack of deletable pages locked.  Start from the
         * top of the tree and move to the bottom, as it's better to release
         * the inner pages as soon as possible.
         */
        if ((ret = __bam_ditem(dbp, epg->page, epg->indx)) != 0)
                goto release;

        /*
         * If we deleted the next-to-last item from the root page, the tree
         * has collapsed a level.  Try and write lock the remaining root + 1
         * page and copy it onto the root page.  If we can't get the lock,
         * that's okay, the tree just stays a level deeper than we'd like.
         */
        h = epg->page;
        if (h->pgno == PGNO_ROOT && NUM_ENT(h) == 1) {
                pgno = TYPE(epg->page) == P_IBTREE ?
                    GET_BINTERNAL(epg->page, 0)->pgno :
                    GET_RINTERNAL(epg->page, 0)->pgno;
                if ((ret = __bam_lget(dbp, 0, pgno, DB_LOCK_WRITE, &lock)) != 0)
                        goto release;
                if ((ret = __bam_pget(dbp, &h, &pgno, 0)) != 0)
                        goto release;

                /* Log the change. */
                if (DB_LOGGING(dbp)) {
                        memset(&a, 0, sizeof(a));
                        a.data = h;
                        a.size = dbp->pgsize;
                        memset(&b, 0, sizeof(b));
                        b.data = P_ENTRY(epg->page, 0);
                        b.size = BINTERNAL_SIZE(((BINTERNAL *)b.data)->len);
                        __bam_rsplit_log(dbp->dbenv->lg_info, dbp->txn,
                           &h->lsn, 0, dbp->log_fileid, h->pgno, &a, &b,
                           &epg->page->lsn);
                }

                /*
                 * Make the switch.
                 *
                 * One fixup -- if the tree has record numbers and we're not
                 * converting to a leaf page, we have to preserve the total
                 * record count.
                 */
                if (TYPE(h) == P_IRECNO ||
                    (TYPE(h) == P_IBTREE && F_ISSET(dbp, DB_BT_RECNUM)))
                        rcnt = RE_NREC(epg->page);
                memcpy(epg->page, h, dbp->pgsize);
                epg->page->pgno = PGNO_ROOT;
                if (TYPE(h) == P_IRECNO ||
                    (TYPE(h) == P_IBTREE && F_ISSET(dbp, DB_BT_RECNUM)))
                        RE_NREC_SET(epg->page, rcnt);

                /* Free the last page in that level of the btree. */
                ++t->lstat.bt_freed;
                (void)__bam_free(dbp, h);

                /* Adjust the cursors. */
                __bam_ca_move(dbp, t, h->pgno, PGNO_ROOT);

                (void)__BT_TLPUT(dbp, lock);
        }

        /* Release the top page in the subtree. */
        (void)memp_fput(dbp->mpf, epg->page, 0);
        (void)__BT_TLPUT(dbp, epg->lock);

        /*
         * Free the rest of the pages.
         *
         * XXX
         * Don't bother checking for errors.  We've unlinked the subtree from
         * the tree, and there's no possibility of recovery.
         */
        for (; ++epg <= t->bt_csp; ++t->lstat.bt_freed) {
                if (NUM_ENT(epg->page) != 0)
                        (void)__bam_ditem(dbp, epg->page, epg->indx);

                (void)__bam_free(dbp, epg->page);
                (void)__BT_TLPUT(dbp, epg->lock);
        }
        return (0);

release:
        /* Discard any remaining pages and return. */
        for (; epg <= t->bt_csp; ++epg) {
                (void)memp_fput(dbp->mpf, epg->page, 0);
                (void)__BT_TLPUT(dbp, epg->lock);
        }
        return (ret);
}