bt_rsearch.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
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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__rsearch_8c-source.html,v 1.1 2008/06/08 10:13:44 sebdiaz Exp $";
#endif /* not lint */

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

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

/*
 * CDB___bam_rsearch --
 *      Search a btree for a record number.
 *
 * PUBLIC: int CDB___bam_rsearch __P((DBC *, db_recno_t *, u_int32_t, int, int *));
 */
int
CDB___bam_rsearch(dbc, recnop, flags, stop, exactp)
        DBC *dbc;
        db_recno_t *recnop;
        u_int32_t flags;
        int stop, *exactp;
{
        BINTERNAL *bi;
        BTREE_CURSOR *cp;
        DB *dbp;
        DB_LOCK lock;
        PAGE *h;
        RINTERNAL *ri;
        db_indx_t adjust, deloffset, indx, top;
        db_lockmode_t lock_mode;
        db_pgno_t pg;
        db_recno_t recno, t_recno, total;
        int ret, stack;

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

        BT_STK_CLR(cp);

        /*
         * There are several ways we search a btree tree.  The flags argument
         * specifies if we're acquiring read or write locks and if we are
         * locking pairs of pages.  In addition, if we're adding or deleting
         * an item, we have to lock the entire tree, regardless.  See btree.h
         * for more details.
         *
         * If write-locking pages, we need to know whether or not to acquire a
         * write lock on a page before getting it.  This depends on how deep it
         * is in tree, which we don't know until we acquire the root page.  So,
         * if we need to lock the root page we may have to upgrade it later,
         * because we won't get the correct lock initially.
         *
         * Retrieve the root page.
         */
        pg = cp->root;
        stack = LF_ISSET(S_STACK);
        lock_mode = stack ? DB_LOCK_WRITE : DB_LOCK_READ;
        if ((ret = CDB___db_lget(dbc, 0, pg, lock_mode, 0, &lock)) != 0)
                return (ret);
        if ((ret = CDB_memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
                /* Did not read it, so we can release the lock */
                (void)__LPUT(dbc, lock);
                return (ret);
        }

        /*
         * Decide if we need to save this page; if we do, write lock it.
         * We deliberately don't lock-couple on this call.  If the tree
         * is tiny, i.e., one page, and two threads are busily updating
         * the root page, we're almost guaranteed deadlocks galore, as
         * each one gets a read lock and then blocks the other's attempt
         * for a write lock.
         */
        if (!stack &&
            ((LF_ISSET(S_PARENT) && (u_int8_t)(stop + 1) >= h->level) ||
            (LF_ISSET(S_WRITE) && h->level == LEAFLEVEL))) {
                (void)CDB_memp_fput(dbp->mpf, h, 0);
                (void)__LPUT(dbc, lock);
                lock_mode = DB_LOCK_WRITE;
                if ((ret = CDB___db_lget(dbc, 0, pg, lock_mode, 0, &lock)) != 0)
                        return (ret);
                if ((ret = CDB_memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
                        /* Did not read it, so we can release the lock */
                        (void)__LPUT(dbc, lock);
                        return (ret);
                }
                stack = 1;
        }

        /*
         * If appending to the tree, set the record number now -- we have the
         * root page locked.
         *
         * Delete only deletes exact matches, read only returns exact matches.
         * Note, this is different from CDB___bam_search(), which returns non-exact
         * matches for read.
         *
         * The record may not exist.  We can only return the correct location
         * for the record immediately after the last record in the tree, so do
         * a fast check now.
         */
        total = RE_NREC(h);
        if (LF_ISSET(S_APPEND)) {
                *exactp = 0;
                *recnop = recno = total + 1;
        } else {
                recno = *recnop;
                if (recno <= total)
                        *exactp = 1;
                else {
                        *exactp = 0;
                        if (!LF_ISSET(S_PAST_EOF) || recno > total + 1) {
                                /*
                                 * Keep the page locked for serializability.
                                 *
                                 * XXX
                                 * This leaves the root page locked, which will
                                 * eliminate any concurrency.  A possible fix
                                 * would be to lock the last leaf page instead.
                                 */
                                (void)CDB_memp_fput(dbp->mpf, h, 0);
                                (void)__TLPUT(dbc, lock);
                                return (DB_NOTFOUND);
                        }
                }
        }

        /*
         * !!!
         * Record numbers in the tree are 0-based, but the recno is
         * 1-based.  All of the calculations below have to take this
         * into account.
         */
        for (total = 0;;) {
                switch (TYPE(h)) {
                case P_LBTREE:
                case P_LDUP:
                        recno -= total;
                        /*
                         * There may be logically deleted records on the page.
                         * If there are enough, the record may not exist.
                         */
                        if (TYPE(h) == P_LBTREE) {
                                adjust = P_INDX;
                                deloffset = O_INDX;
                        } else {
                                adjust = O_INDX;
                                deloffset = 0;
                        }
                        for (t_recno = 0, indx = 0;; indx += adjust) {
                                if (indx >= NUM_ENT(h)) {
                                        *exactp = 0;
                                        if (!LF_ISSET(S_PAST_EOF) ||
                                            recno > t_recno + 1) {
                                                ret = DB_NOTFOUND;
                                                goto err;
                                        }
                                }
                                if (!B_DISSET(
                                    GET_BKEYDATA(h, indx + deloffset)->type) &&
                                    ++t_recno == recno)
                                        break;
                        }

                        /* Correct from 1-based to 0-based for a page offset. */
                        BT_STK_ENTER(dbp->dbenv,
                            cp, h, indx, lock, lock_mode, ret);
                        if (ret != 0)
                                goto err;
                        return (0);
                case P_IBTREE:
                        for (indx = 0, top = NUM_ENT(h);;) {
                                bi = GET_BINTERNAL(h, indx);
                                if (++indx == top || total + bi->nrecs >= recno)
                                        break;
                                total += bi->nrecs;
                        }
                        pg = bi->pgno;
                        break;
                case P_LRECNO:
                        recno -= total;

                        /* Correct from 1-based to 0-based for a page offset. */
                        --recno;
                        BT_STK_ENTER(dbp->dbenv,
                            cp, h, recno, lock, lock_mode, ret);
                        if (ret != 0)
                                goto err;
                        return (0);
                case P_IRECNO:
                        for (indx = 0, top = NUM_ENT(h);;) {
                                ri = GET_RINTERNAL(h, indx);
                                if (++indx == top || total + ri->nrecs >= recno)
                                        break;
                                total += ri->nrecs;
                        }
                        pg = ri->pgno;
                        break;
                default:
                        return (CDB___db_pgfmt(dbp, h->pgno));
                }
                --indx;

                if (stack) {
                        /* Return if this is the lowest page wanted. */
                        if (LF_ISSET(S_PARENT) && stop == h->level) {
                                BT_STK_ENTER(dbp->dbenv,
                                    cp, h, indx, lock, lock_mode, ret);
                                if (ret != 0)
                                        goto err;
                                return (0);
                        }
                        BT_STK_PUSH(dbp->dbenv,
                            cp, h, indx, lock, lock_mode, ret);
                        if (ret != 0)
                                goto err;

                        lock_mode = DB_LOCK_WRITE;
                        if ((ret =
                            CDB___db_lget(dbc, 0, pg, lock_mode, 0, &lock)) != 0)
                                goto err;
                } else {
                        /*
                         * Decide if we want to return a pointer to the next
                         * page in the stack.  If we do, write lock it and
                         * never unlock it.
                         */
                        if ((LF_ISSET(S_PARENT) &&
                            (u_int8_t)(stop + 1) >= (u_int8_t)(h->level - 1)) ||
                            (h->level - 1) == LEAFLEVEL)
                                stack = 1;

                        (void)CDB_memp_fput(dbp->mpf, h, 0);

                        lock_mode = stack &&
                            LF_ISSET(S_WRITE) ? DB_LOCK_WRITE : DB_LOCK_READ;
                        if ((ret = CDB___db_lget(dbc,
                            LCK_COUPLE, pg, lock_mode, 0, &lock)) != 0) {
                                /*
                                 * If we fail, discard the lock we held.  This
                                 * is OK because this only happens when we are
                                 * descending the tree holding read-locks.
                                 */
                                __LPUT(dbc, lock);
                                goto err;
                        }
                }

                if ((ret = CDB_memp_fget(dbp->mpf, &pg, 0, &h)) != 0)
                        goto err;
        }
        /* NOTREACHED */

err:    BT_STK_POP(cp);
        CDB___bam_stkrel(dbc, 0);
        return (ret);
}

/*
 * CDB___bam_adjust --
 *      Adjust the tree after adding or deleting a record.
 *
 * PUBLIC: int CDB___bam_adjust __P((DBC *, int32_t));
 */
int
CDB___bam_adjust(dbc, adjust)
        DBC *dbc;
        int32_t adjust;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        EPG *epg;
        PAGE *h;
        db_pgno_t root_pgno;
        int ret;

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;
        root_pgno = cp->root;

        /* Update the record counts for the tree. */
        for (epg = cp->sp; epg <= cp->csp; ++epg) {
                h = epg->page;
                if (TYPE(h) == P_IBTREE || TYPE(h) == P_IRECNO) {
                        if (DB_LOGGING(dbc) &&
                            (ret = CDB___bam_cadjust_log(dbp->dbenv,
                            dbc->txn, &LSN(h), 0, dbp->log_fileid,
                            PGNO(h), &LSN(h), (u_int32_t)epg->indx, adjust,
                            PGNO(h) == root_pgno ? CAD_UPDATEROOT : 0)) != 0)
                                return (ret);

                        if (TYPE(h) == P_IBTREE)
                                GET_BINTERNAL(h, epg->indx)->nrecs += adjust;
                        else
                                GET_RINTERNAL(h, epg->indx)->nrecs += adjust;

                        if (PGNO(h) == root_pgno)
                                RE_NREC_ADJ(h, adjust);

                        if ((ret = CDB_memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY)) != 0)
                                return (ret);
                }
        }
        return (0);
}

/*
 * CDB___bam_nrecs --
 *      Return the number of records in the tree.
 *
 * PUBLIC: int CDB___bam_nrecs __P((DBC *, db_recno_t *));
 */
int
CDB___bam_nrecs(dbc, rep)
        DBC *dbc;
        db_recno_t *rep;
{
        DB *dbp;
        DB_LOCK lock;
        PAGE *h;
        db_pgno_t pgno;
        int ret;

        dbp = dbc->dbp;

        pgno = dbc->internal->root;
        if ((ret = CDB___db_lget(dbc, 0, pgno, DB_LOCK_READ, 0, &lock)) != 0)
                return (ret);
        if ((ret = CDB_memp_fget(dbp->mpf, &pgno, 0, &h)) != 0)
                return (ret);

        *rep = RE_NREC(h);

        (void)CDB_memp_fput(dbp->mpf, h, 0);
        (void)__TLPUT(dbc, lock);

        return (0);
}

/*
 * CDB___bam_total --
 *      Return the number of records below a page.
 *
 * PUBLIC: db_recno_t CDB___bam_total __P((PAGE *));
 */
db_recno_t
CDB___bam_total(h)
        PAGE *h;
{
        db_recno_t nrecs;
        db_indx_t indx, top;

        nrecs = 0;
        top = NUM_ENT(h);

        switch (TYPE(h)) {
        case P_LBTREE:
                /* Check for logically deleted records. */
                for (indx = 0; indx < top; indx += P_INDX)
                        if (!B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type))
                                ++nrecs;
                break;
        case P_LDUP:
                /* Check for logically deleted records. */
                for (indx = 0; indx < top; indx += O_INDX)
                        if (!B_DISSET(GET_BKEYDATA(h, indx)->type))
                                ++nrecs;
                break;
        case P_IBTREE:
                for (indx = 0; indx < top; indx += O_INDX)
                        nrecs += GET_BINTERNAL(h, indx)->nrecs;
                break;
        case P_LRECNO:
                nrecs = NUM_ENT(h);
                break;
        case P_IRECNO:
                for (indx = 0; indx < top; indx += O_INDX)
                        nrecs += GET_RINTERNAL(h, indx)->nrecs;
                break;
        }

        return (nrecs);
}

---