bt_delete.c

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/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998, 1999, 2000
 *      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.
 */

#include "config.h"

#ifndef lint
static const char revid[] = "$Id: bt__delete_8c-source.html,v 1.1 2008/06/08 10:13:35 sebdiaz Exp $";
#endif /* not lint */

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

#include <string.h>
#endif

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

/*
 * CDB___bam_delete --
 *      Delete the items referenced by a key.
 *
 * PUBLIC: int CDB___bam_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
 */
int
CDB___bam_delete(dbp, txn, key, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key;
        u_int32_t flags;
{
        DBC *dbc;
        DBT lkey;
        DBT data;
        u_int32_t f_init, f_next;
        int ret, t_ret;

        PANIC_CHECK(dbp->dbenv);
        DB_ILLEGAL_BEFORE_OPEN(dbp, "DB->del");

        /* Check for invalid flags. */
        if ((ret =
            CDB___db_delchk(dbp, key, flags, F_ISSET(dbp, DB_AM_RDONLY))) != 0)
                return (ret);

        /* Allocate a cursor. */
        if ((ret = dbp->cursor(dbp, txn, &dbc, DB_WRITELOCK)) != 0)
                return (ret);

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

        /*
         * Walk a cursor through the key/data pairs, deleting as we go.  Set
         * the DB_DBT_USERMEM flag, as this might be a threaded application
         * and the flags checking will catch us.  We don't actually want the
         * keys or data, so request a partial of length 0.
         */
        memset(&lkey, 0, sizeof(lkey));
        F_SET(&lkey, DB_DBT_USERMEM | DB_DBT_PARTIAL);
        memset(&data, 0, sizeof(data));
        F_SET(&data, DB_DBT_USERMEM | DB_DBT_PARTIAL);

        /*
         * If locking (and we haven't already acquired CDB locks), set the
         * read-modify-write flag.
         */
        f_init = DB_SET;
        f_next = DB_NEXT_DUP;
        if (STD_LOCKING(dbc)) {
                f_init |= DB_RMW;
                f_next |= DB_RMW;
        }

        /* Walk through the set of key/data pairs, deleting as we go. */
        if ((ret = dbc->c_get(dbc, key, &data, f_init)) != 0)
                goto err;
        for (;;) {
                if ((ret = dbc->c_del(dbc, 0)) != 0)
                        goto err;
                if ((ret = dbc->c_get(dbc, &lkey, &data, f_next)) != 0) {
                        if (ret == DB_NOTFOUND) {
                                ret = 0;
                                break;
                        }
                        goto err;
                }
        }

err:    /* Discard the cursor. */
        if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
                ret = t_ret;

        return (ret);
}

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

        dbp = dbc->dbp;

        switch (TYPE(h)) {
        case P_IBTREE:
                bi = GET_BINTERNAL(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 =
                            CDB___db_doff(dbc, ((BOVERFLOW *)bi->data)->pgno)) != 0)
                                return (ret);
                        break;
                default:
                        return (CDB___db_pgfmt(dbp, 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) &&
                            h->inp[indx] == h->inp[indx + P_INDX])
                                return (CDB___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 && h->inp[indx] == h->inp[indx - P_INDX])
                                return (CDB___bam_adjindx(dbc,
                                    h, indx, indx - P_INDX, 0));
                }
                /* FALLTHROUGH */
        case P_LDUP:
        case P_LRECNO:
                bk = GET_BKEYDATA(h, indx);
                switch (B_TYPE(bk->type)) {
                case B_DUPLICATE:
                        nbytes = BOVERFLOW_SIZE;
                        break;
                case B_OVERFLOW:
                        nbytes = BOVERFLOW_SIZE;
                        if ((ret = CDB___db_doff(
                            dbc, (GET_BOVERFLOW(h, indx))->pgno)) != 0)
                                return (ret);
                        break;
                case B_KEYDATA:
                        nbytes = BKEYDATA_SIZE(bk->len);
                        break;
                default:
                        return (CDB___db_pgfmt(dbp, PGNO(h)));
                }
                break;
        default:
                return (CDB___db_pgfmt(dbp, PGNO(h)));
        }

        /* Delete the item and mark the page dirty. */
        if ((ret = CDB___db_ditem(dbc, h, indx, nbytes)) != 0)
                return (ret);
        if ((ret = CDB_memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY)) != 0)
                return (ret);

        return (0);
}

/*
 * CDB___bam_adjindx --
 *      Adjust an index on the page.
 *
 * PUBLIC: int CDB___bam_adjindx __P((DBC *, PAGE *, u_int32_t, u_int32_t, int));
 */
int
CDB___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_indx_t copy;
        int ret;

        dbp = dbc->dbp;

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

        /* Shuffle the indices and mark the page dirty. */
        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));
        }
        if ((ret = CDB_memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY)) != 0)
                return (ret);

        return (0);
}

/*
 * CDB___bam_dpages --
 *      Delete a set of locked pages.
 *
 * PUBLIC: int CDB___bam_dpages __P((DBC *, EPG *));
 */
int
CDB___bam_dpages(dbc, stack_epg)
        DBC *dbc;
        EPG *stack_epg;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        DBT a, b;
        DB_LOCK c_lock, p_lock;
        EPG *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;
        cp = (BTREE_CURSOR *)dbc->internal;

        /*
         * We have the entire stack of deletable pages locked.
         *
         * Btree calls us with a pointer to the beginning of a stack, where
         * the first page in the stack is to have a single item deleted, and
         * the rest of the pages are to be removed.
         *
         * Recno calls us with a pointer into the middle of the stack, where
         * the referenced page is to have a single item deleted, and pages
         * after the stack reference are to be removed.
         *
         * First, discard any pages that we don't care about.
         */
        ret = 0;
        for (epg = cp->sp; epg < stack_epg; ++epg) {
                if ((t_ret =
                    CDB_memp_fput(dbp->mpf, epg->page, 0)) != 0 && ret == 0)
                        ret = t_ret;
                (void)__TLPUT(dbc, epg->lock);
        }
        if (ret != 0)
                goto err;

        /*
         * !!!
         * 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 ((ret = CDB___db_relink(dbc, DB_REM_PAGE, cp->csp->page, NULL, 1)) != 0)
                goto err;

        /*
         * 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 = CDB___bam_ditem(dbc, epg->page, epg->indx)) != 0)
                goto err;
        CDB___bam_ca_di(dbp, PGNO(epg->page), epg->indx, -1);

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

        if ((ret = CDB_memp_fput(dbp->mpf, epg->page, 0)) != 0)
                goto err_inc;
        (void)__TLPUT(dbc, epg->lock);

        /* 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(NUM_ENT(epg->page) == 1);

                        if ((ret = CDB___bam_ditem(dbc, epg->page, epg->indx)) != 0)
                                goto err;
                }

                if ((ret = CDB___db_free(dbc, epg->page)) != 0)
                        goto err_inc;
                (void)__TLPUT(dbc, epg->lock);
        }

        if (0) {
err_inc:        ++epg;
err:            for (; epg <= cp->csp; ++epg) {
                        (void)CDB_memp_fput(dbp->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.  If we can't get a
         * write lock, that's okay, the tree just stays deeper than we'd like.
         */
        root_pgno = cp->root;
        if (pgno != root_pgno || nitems != 1)
                return (0);

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

                /* Lock the root. */
                pgno = root_pgno;
                if ((ret =
                    CDB___db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &p_lock)) != 0)
                        goto stop;
                if ((ret = CDB_memp_fget(dbp->mpf, &pgno, 0, &parent)) != 0)
                        goto stop;

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

                switch (TYPE(parent)) {
                case P_IBTREE:
                        pgno = GET_BINTERNAL(parent, 0)->pgno;
                        break;
                case P_IRECNO:
                        pgno = GET_RINTERNAL(parent, 0)->pgno;
                        break;
                default:
                        goto stop;
                }

                /* Lock the child page. */
                if ((ret =
                    CDB___db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &c_lock)) != 0)
                        goto stop;
                if ((ret = CDB_memp_fget(dbp->mpf, &pgno, 0, &child)) != 0)
                        goto stop;

                /* Log the change. */
                if (DB_LOGGING(dbc)) {
                        memset(&a, 0, sizeof(a));
                        a.data = child;
                        a.size = dbp->pgsize;
                        memset(&b, 0, sizeof(b));
                        b.data = P_ENTRY(parent, 0);
                        b.size = BINTERNAL_SIZE(((BINTERNAL *)b.data)->len);
                        CDB___bam_rsplit_log(dbp->dbenv, dbc->txn,
                           &child->lsn, 0, dbp->log_fileid, PGNO(child), &a,
                           PGNO(parent), RE_NREC(parent), &b, &parent->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. */
                CDB_memp_fset(dbp->mpf, parent, DB_MPOOL_DIRTY);
                CDB_memp_fset(dbp->mpf, child, DB_MPOOL_DIRTY);

                /* Adjust the cursors. */
                CDB___bam_ca_rsplit(dbp, PGNO(child), root_pgno);

                /*
                 * Free the page copied onto the root page and discard its
                 * lock.  (The call to CDB___db_free() discards our reference
                 * to the page.)
                 */
                (void)CDB___db_free(dbc, child);
                child = NULL;

                if (0) {
stop:                   done = 1;
                }
                if (p_lock.off != LOCK_INVALID)
                        (void)__TLPUT(dbc, p_lock);
                if (parent != NULL)
                        CDB_memp_fput(dbp->mpf, parent, 0);
                if (c_lock.off != LOCK_INVALID)
                        (void)__TLPUT(dbc, c_lock);
                if (child != NULL)
                        CDB_memp_fput(dbp->mpf, child, 0);
        }

        return (0);
}

---