bt_delete.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      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. 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.
 *
 * $Id: bt_delete.c,v 12.13 2005/10/20 18:14:59 bostic Exp $
 */

#include "db_config.h"

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

#include <string.h>
#endif

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/db_shash.h"
#include "dbinc/btree.h"
#include "dbinc/lock.h"
#include "dbinc/mp.h"

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

        dbp = dbc->dbp;
        mpf = dbp->mpf;
        inp = P_INP(dbp, h);

        switch (TYPE(h)) {
        case P_IBTREE:
                bi = GET_BINTERNAL(dbp, h, indx);
                switch (B_TYPE(bi->type)) {
                case B_DUPLICATE:
                case B_KEYDATA:
                        nbytes = BINTERNAL_SIZE(bi->len);
                        break;
                case B_OVERFLOW:
                        nbytes = BINTERNAL_SIZE(bi->len);
                        if ((ret =
                            __db_doff(dbc, ((BOVERFLOW *)bi->data)->pgno)) != 0)
                                return (ret);
                        break;
                default:
                        return (__db_pgfmt(dbp->dbenv, PGNO(h)));
                }
                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 matching
                 * any other index so even if the data item is in a key "slot",
                 * it won't match any other index.
                 */
                if ((indx % 2) == 0) {
                        /*
                         * Check for a duplicate after us on the page.  NOTE:
                         * we have to delete the key item before deleting the
                         * data item, otherwise the "indx + P_INDX" calculation
                         * won't work!
                         */
                        if (indx + P_INDX < (u_int32_t)NUM_ENT(h) &&
                            inp[indx] == inp[indx + P_INDX])
                                return (__bam_adjindx(dbc,
                                    h, indx, indx + O_INDX, 0));
                        /*
                         * Check for a duplicate before us on the page.  It
                         * doesn't matter if we delete the key item before or
                         * after the data item for the purposes of this one.
                         */
                        if (indx > 0 && inp[indx] == inp[indx - P_INDX])
                                return (__bam_adjindx(dbc,
                                    h, indx, indx - P_INDX, 0));
                }
                /* FALLTHROUGH */
        case P_LDUP:
        case P_LRECNO:
                bk = GET_BKEYDATA(dbp, h, indx);
                switch (B_TYPE(bk->type)) {
                case B_DUPLICATE:
                        nbytes = BOVERFLOW_SIZE;
                        break;
                case B_OVERFLOW:
                        nbytes = BOVERFLOW_SIZE;
                        if ((ret = __db_doff(
                            dbc, (GET_BOVERFLOW(dbp, h, indx))->pgno)) != 0)
                                return (ret);
                        break;
                case B_KEYDATA:
                        nbytes = BKEYDATA_SIZE(bk->len);
                        break;
                default:
                        return (__db_pgfmt(dbp->dbenv, PGNO(h)));
                }
                break;
        default:
                return (__db_pgfmt(dbp->dbenv, PGNO(h)));
        }

        /* Delete the item and mark the page dirty. */
        if ((ret = __db_ditem(dbc, h, indx, nbytes)) != 0)
                return (ret);
        if ((ret = __memp_fset(mpf, h, DB_MPOOL_DIRTY)) != 0)
                return (ret);

        return (0);
}

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

        dbp = dbc->dbp;
        mpf = dbp->mpf;
        inp = P_INP(dbp, h);

        /* Log the change. */
        if (DBC_LOGGING(dbc)) {
            if ((ret = __bam_adj_log(dbp, dbc->txn, &LSN(h), 0,
                PGNO(h), &LSN(h), indx, indx_copy, (u_int32_t)is_insert)) != 0)
                        return (ret);
        } else
                LSN_NOT_LOGGED(LSN(h));

        /* Shuffle the indices and mark the page dirty. */
        if (is_insert) {
                copy = inp[indx_copy];
                if (indx != NUM_ENT(h))
                        memmove(&inp[indx + O_INDX], &inp[indx],
                            sizeof(db_indx_t) * (NUM_ENT(h) - indx));
                inp[indx] = copy;
                ++NUM_ENT(h);
        } else {
                --NUM_ENT(h);
                if (indx != NUM_ENT(h))
                        memmove(&inp[indx], &inp[indx + O_INDX],
                            sizeof(db_indx_t) * (NUM_ENT(h) - indx));
        }
        if ((ret = __memp_fset(mpf, h, DB_MPOOL_DIRTY)) != 0)
                return (ret);

        return (0);
}

/*
 * __bam_dpages --
 *      Delete a set of locked pages.
 *
 * PUBLIC: int __bam_dpages __P((DBC *, int, int));
 */
int
__bam_dpages(dbc, use_top, update)
        DBC *dbc;
        int use_top;
        int update;
{
        BTREE_CURSOR *cp;
        BINTERNAL *bi;
        DB *dbp;
        DBT a, b;
        DB_LOCK c_lock, p_lock;
        DB_MPOOLFILE *mpf;
        EPG *epg, *save_sp, *stack_epg;
        PAGE *child, *parent;
        db_indx_t nitems;
        db_pgno_t pgno, root_pgno;
        db_recno_t rcnt;
        int done, ret, t_ret;

        dbp = dbc->dbp;
        mpf = dbp->mpf;
        cp = (BTREE_CURSOR *)dbc->internal;
        nitems = 0;
        pgno = PGNO_INVALID;

        /*
         * We have the entire stack of deletable pages locked.
         *
         * Btree calls us with the first page in the stack is to have a
         * single item deleted, and the rest of the pages are to be removed.
         *
         * Recno always has a stack to the root and __bam_merge operations
         * may have unneeded items in the sack.  We find the lowest page
         * in the stack that has more than one record in it and start there.
         */
        ret = 0;
        if (use_top)
                stack_epg = cp->sp;
        else
                for (stack_epg = cp->csp; stack_epg > cp->sp; --stack_epg)
                        if (NUM_ENT(stack_epg->page) > 1)
                                break;
        epg = stack_epg;
        /*
         * !!!
         * 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.  Before we unlink the subtree, we relink the
         * leaf page chain.
         */
        if (LEVEL(cp->csp->page) == 1 &&
            (ret = __bam_relink(dbc, cp->csp->page, PGNO_INVALID)) != 0)
                goto discard;

        /*
         * Delete the last item that references the underlying pages that are
         * to be deleted, and adjust cursors that reference that page.  Then,
         * save that page's page number and item count and release it.  If
         * the application isn't retaining locks because it's running without
         * transactions, this lets the rest of the tree get back to business
         * immediately.
         */
        if ((ret = __bam_ditem(dbc, epg->page, epg->indx)) != 0)
                goto discard;
        if ((ret = __bam_ca_di(dbc, PGNO(epg->page), epg->indx, -1)) != 0)
                goto discard;

        if (update && epg->indx == 0) {
                save_sp = cp->csp;
                cp->csp = epg;
                ret = __bam_pupdate(dbc, epg->page);
                cp->csp = save_sp;
                if (ret != 0)
                        goto discard;
        }

        pgno = PGNO(epg->page);
        nitems = NUM_ENT(epg->page);

        ret = __memp_fput(mpf, epg->page, 0);
        if ((t_ret = __TLPUT(dbc, epg->lock)) != 0 && ret == 0)
                ret = t_ret;
        if (ret != 0)
                goto err_inc;

        /* Then, discard any pages that we don't care about. */
discard: for (epg = cp->sp; epg < stack_epg; ++epg) {
                if ((t_ret = __memp_fput(mpf, epg->page, 0)) != 0 && ret == 0)
                        ret = t_ret;
                epg->page = NULL;
                if ((t_ret = __TLPUT(dbc, epg->lock)) != 0 && ret == 0)
                        ret = t_ret;
        }
        if (ret != 0)
                goto err;

        /* Free the rest of the pages in the stack. */
        while (++epg <= cp->csp) {
                /*
                 * Delete page entries so they will be restored as part of
                 * recovery.  We don't need to do cursor adjustment here as
                 * the pages are being emptied by definition and so cannot
                 * be referenced by a cursor.
                 */
                if (NUM_ENT(epg->page) != 0) {
                        DB_ASSERT(LEVEL(epg->page) != 1);

                        if ((ret = __bam_ditem(dbc, epg->page, epg->indx)) != 0)
                                goto err;
                        /*
                         * Sheer paranoia: if we find any pages that aren't
                         * emptied by the delete, someone else added an item
                         * while we were walking the tree, and we discontinue
                         * the delete.  Shouldn't be possible, but we check
                         * regardless.
                         */
                        if (NUM_ENT(epg->page) != 0)
                                goto err;
                }

                ret = __db_free(dbc, epg->page);
                if (cp->page == epg->page)
                        cp->page = NULL;
                epg->page = NULL;
                if ((t_ret = __TLPUT(dbc, epg->lock)) != 0 && ret == 0)
                        ret = t_ret;
                if (ret != 0)
                        goto err_inc;
        }

        if (0) {
err_inc:        ++epg;
err:            for (; epg <= cp->csp; ++epg) {
                        if (epg->page != NULL)
                                (void)__memp_fput(mpf, epg->page, 0);
                        (void)__TLPUT(dbc, epg->lock);
                }
                BT_STK_CLR(cp);
                return (ret);
        }
        BT_STK_CLR(cp);

        /*
         * If we just deleted the next-to-last item from the root page, the
         * tree can collapse one or more levels.  While there remains only a
         * single item on the root page, write lock the last page referenced
         * by the root page and copy it over the root page.
         */
        root_pgno = cp->root;
        if (pgno != root_pgno || nitems != 1)
                return (0);

        for (done = 0; !done;) {
                /* Initialize. */
                parent = child = NULL;
                LOCK_INIT(p_lock);
                LOCK_INIT(c_lock);

                /* Lock the root. */
                pgno = root_pgno;
                if ((ret =
                    __db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &p_lock)) != 0)
                        goto stop;
                if ((ret = __memp_fget(mpf, &pgno, 0, &parent)) != 0)
                        goto stop;

                if (NUM_ENT(parent) != 1)
                        goto stop;

                switch (TYPE(parent)) {
                case P_IBTREE:
                        /*
                         * If this is overflow, then try to delete it.
                         * The child may or may not still point at it.
                         */
                        bi = GET_BINTERNAL(dbp, parent, 0);
                        if (B_TYPE(bi->type) == B_OVERFLOW)
                                if ((ret = __db_doff(dbc,
                                    ((BOVERFLOW *)bi->data)->pgno)) != 0)
                                        goto stop;
                        pgno = bi->pgno;
                        break;
                case P_IRECNO:
                        pgno = GET_RINTERNAL(dbp, parent, 0)->pgno;
                        break;
                default:
                        goto stop;
                }

                /* Lock the child page. */
                if ((ret =
                    __db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &c_lock)) != 0)
                        goto stop;
                if ((ret = __memp_fget(mpf, &pgno, 0, &child)) != 0)
                        goto stop;

                /* Log the change. */
                if (DBC_LOGGING(dbc)) {
                        memset(&a, 0, sizeof(a));
                        a.data = child;
                        a.size = dbp->pgsize;
                        memset(&b, 0, sizeof(b));
                        b.data = P_ENTRY(dbp, parent, 0);
                        b.size = TYPE(parent) == P_IRECNO ? RINTERNAL_SIZE :
                            BINTERNAL_SIZE(((BINTERNAL *)b.data)->len);
                        if ((ret = __bam_rsplit_log(dbp, dbc->txn,
                            &child->lsn, 0, PGNO(child), &a, PGNO(parent),
                            RE_NREC(parent), &b, &parent->lsn)) != 0)
                                goto stop;
                } else
                        LSN_NOT_LOGGED(child->lsn);

                /*
                 * Make the switch.
                 *
                 * One fixup -- internal pages below the top level do not store
                 * a record count, so we have to preserve it if we're not
                 * converting to a leaf page.  Note also that we are about to
                 * overwrite the parent page, including its LSN.  This is OK
                 * because the log message we wrote describing this update
                 * stores its LSN on the child page.  When the child is copied
                 * onto the parent, the correct LSN is copied into place.
                 */
                COMPQUIET(rcnt, 0);
                if (F_ISSET(cp, C_RECNUM) && LEVEL(child) > LEAFLEVEL)
                        rcnt = RE_NREC(parent);
                memcpy(parent, child, dbp->pgsize);
                PGNO(parent) = root_pgno;
                if (F_ISSET(cp, C_RECNUM) && LEVEL(child) > LEAFLEVEL)
                        RE_NREC_SET(parent, rcnt);

                /* Mark the pages dirty. */
                if ((ret = __memp_fset(mpf, parent, DB_MPOOL_DIRTY)) != 0)
                        goto stop;
                if ((ret = __memp_fset(mpf, child, DB_MPOOL_DIRTY)) != 0)
                        goto stop;

                /* Adjust the cursors. */
                if ((ret = __bam_ca_rsplit(dbc, PGNO(child), root_pgno)) != 0)
                        goto stop;

                /*
                 * Free the page copied onto the root page and discard its
                 * lock.  (The call to __db_free() discards our reference
                 * to the page.)
                 */
                if ((ret = __db_free(dbc, child)) != 0) {
                        child = NULL;
                        goto stop;
                }
                child = NULL;

                if (0) {
stop:                   done = 1;
                }
                if ((t_ret = __TLPUT(dbc, p_lock)) != 0 && ret == 0)
                        ret = t_ret;
                if (parent != NULL &&
                    (t_ret = __memp_fput(mpf, parent, 0)) != 0 && ret == 0)
                        ret = t_ret;
                if ((t_ret = __TLPUT(dbc, c_lock)) != 0 && ret == 0)
                        ret = t_ret;
                if (child != NULL &&
                    (t_ret = __memp_fput(mpf, child, 0)) != 0 && ret == 0)
                        ret = t_ret;
        }

        return (ret);
}

/*
 * __bam_relink --
 *      Relink around a deleted page.
 *
 * PUBLIC: int __bam_relink __P((DBC *, PAGE *, db_pgno_t));
 */
int
__bam_relink(dbc, pagep, new_pgno)
        DBC *dbc;
        PAGE *pagep;
        db_pgno_t new_pgno;
{
        DB *dbp;
        PAGE *np, *pp;
        DB_LOCK npl, ppl;
        DB_LSN *nlsnp, *plsnp, ret_lsn;
        DB_MPOOLFILE *mpf;
        int ret, t_ret;

        dbp = dbc->dbp;
        np = pp = NULL;
        LOCK_INIT(npl);
        LOCK_INIT(ppl);
        nlsnp = plsnp = NULL;
        mpf = dbp->mpf;
        ret = 0;

        /*
         * Retrieve and lock the one/two pages.  For a remove, we may need
         * two pages (the before and after).  For an add, we only need one
         * because, the split took care of the prev.
         */
        if (pagep->next_pgno != PGNO_INVALID) {
                if ((ret = __db_lget(dbc,
                    0, pagep->next_pgno, DB_LOCK_WRITE, 0, &npl)) != 0)
                        goto err;
                if ((ret = __memp_fget(mpf, &pagep->next_pgno, 0, &np)) != 0) {
                        ret = __db_pgerr(dbp, pagep->next_pgno, ret);
                        goto err;
                }
                nlsnp = &np->lsn;
        }
        if (pagep->prev_pgno != PGNO_INVALID) {
                if ((ret = __db_lget(dbc,
                    0, pagep->prev_pgno, DB_LOCK_WRITE, 0, &ppl)) != 0)
                        goto err;
                if ((ret = __memp_fget(mpf, &pagep->prev_pgno, 0, &pp)) != 0) {
                        ret = __db_pgerr(dbp, pagep->prev_pgno, ret);
                        goto err;
                }
                plsnp = &pp->lsn;
        }

        /* Log the change. */
        if (DBC_LOGGING(dbc)) {
                if ((ret = __bam_relink_log(dbp, dbc->txn, &ret_lsn, 0,
                    pagep->pgno, new_pgno, pagep->prev_pgno, plsnp,
                    pagep->next_pgno, nlsnp)) != 0)
                        goto err;
        } else
                LSN_NOT_LOGGED(ret_lsn);
        if (np != NULL)
                np->lsn = ret_lsn;
        if (pp != NULL)
                pp->lsn = ret_lsn;

        /*
         * Modify and release the two pages.
         */
        if (np != NULL) {
                if (new_pgno == PGNO_INVALID)
                        np->prev_pgno = pagep->prev_pgno;
                else
                        np->prev_pgno = new_pgno;
                ret = __memp_fput(mpf, np, DB_MPOOL_DIRTY);
                if ((t_ret = __TLPUT(dbc, npl)) != 0 && ret == 0)
                        ret = t_ret;
                if (ret != 0)
                        goto err;
        }

        if (pp != NULL) {
                if (new_pgno == PGNO_INVALID)
                        pp->next_pgno = pagep->next_pgno;
                else
                        pp->next_pgno = new_pgno;
                ret = __memp_fput(mpf, pp, DB_MPOOL_DIRTY);
                if ((t_ret = __TLPUT(dbc, ppl)) != 0 && ret == 0)
                        ret = t_ret;
                if (ret != 0)
                        goto err;
        }
        return (0);

err:    if (np != NULL)
                (void)__memp_fput(mpf, np, 0);
        (void)__TLPUT(dbc, npl);
        if (pp != NULL)
                (void)__memp_fput(mpf, pp, 0);
        (void)__TLPUT(dbc, ppl);
        return (ret);
}

/*
 * __bam_pupdate --
 *      Update parent key pointers up the tree.
 *
 * PUBLIC: int __bam_pupdate __P((DBC *, PAGE *));
 */
int
__bam_pupdate(dbc, lpg)
        DBC *dbc;
        PAGE *lpg;
{
        BTREE_CURSOR *cp;
        DB_ENV *dbenv;
        EPG *epg;
        int ret;

        dbenv = dbc->dbp->dbenv;
        cp = (BTREE_CURSOR *)dbc->internal;
        ret = 0;

        /*
         * Update the parents up the tree.  __bam_pinsert only looks at the
         * left child if is a leaf page, so we don't need to change it.  We
         * just do a delete and insert; a replace is possible but reusing
         * pinsert is better.
         */
        for (epg = &cp->csp[-1]; epg >= cp->sp; epg--) {
                if ((ret = __bam_ditem(dbc, epg->page, epg->indx)) != 0)
                        return (ret);
                epg->indx--;
                if ((ret = __bam_pinsert(dbc, epg,
                    lpg, epg[1].page, BPI_NORECNUM)) != 0) {
                        if (ret == DB_NEEDSPLIT) {
                                /* This should not happen. */
                                __db_err(dbenv,
                                     "Not enough room in parent: %s: page %lu",
                                     dbc->dbp->fname, (u_long)PGNO(epg->page));
                                ret = __db_panic(dbenv, EINVAL);
                        }
                        return (ret);
                }
        }
        return (ret);
}

---