db/btree/bt_search.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *  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_search.c   10.25 (Sleepycat) 12/16/98";
#endif /* not lint */

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

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

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

/*
 * __bam_search --
 *  Search a btree for a key.
 *
 * PUBLIC: int __bam_search __P((DBC *,
 * PUBLIC:     const DBT *, u_int32_t, int, db_recno_t *, int *));
 */
int
__bam_search(dbc, key, flags, stop, recnop, exactp)
    DBC *dbc;
    const DBT *key;
    u_int32_t flags;
    int stop, *exactp;
    db_recno_t *recnop;
{
    BTREE *t;
    CURSOR *cp;
    DB *dbp;
    DB_LOCK lock;
    PAGE *h;
    db_indx_t base, i, indx, lim;
    db_pgno_t pg;
    db_recno_t recno;
    int cmp, jump, ret, stack;

    dbp = dbc->dbp;
    cp = dbc->internal;
    t = dbp->internal;
    recno = 0;

    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, if we position
     * to the first or last item in a set of duplicates, if we return
     * deleted items, and if we are locking pairs of pages.  In addition,
     * if we're modifying record numbers, 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 = PGNO_ROOT;
    stack = F_ISSET(dbp, DB_BT_RECNUM) && LF_ISSET(S_STACK);
    if ((ret = __bam_lget(dbc,
        0, pg, stack ? DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
        return (ret);
    if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
        (void)__BT_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)memp_fput(dbp->mpf, h, 0);
        (void)__BT_LPUT(dbc, lock);
        if ((ret = __bam_lget(dbc, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
            return (ret);
        if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0) {
            (void)__BT_LPUT(dbc, lock);
            return (ret);
        }
        stack = 1;
    }

    for (;;) {
        /*
         * Do a binary search on the current page.  If we're searching
         * a leaf page, we have to manipulate the indices in groups of
         * two.  If we're searching an internal page, they're an index
         * per page item.  If we find an exact match on a leaf page,
         * we're done.
         */
        jump = TYPE(h) == P_LBTREE ? P_INDX : O_INDX;
        for (base = 0,
            lim = NUM_ENT(h) / (db_indx_t)jump; lim != 0; lim >>= 1) {
            indx = base + ((lim >> 1) * jump);
            if ((cmp =
                __bam_cmp(dbp, key, h, indx, t->bt_compare)) == 0) {
                if (TYPE(h) == P_LBTREE)
                    goto match;
                goto next;
            }
            if (cmp > 0) {
                base = indx + jump;
                --lim;
            }
        }

        /*
         * No match found.  Base is the smallest index greater than
         * key and may be zero or a last + O_INDX index.
         *
         * If it's a leaf page, return base as the "found" value.
         * Delete only deletes exact matches.
         */
        if (TYPE(h) == P_LBTREE) {
            *exactp = 0;

            if (LF_ISSET(S_EXACT))
                goto notfound;

            /*
             * !!!
             * Possibly returning a deleted record -- DB_SET_RANGE,
             * DB_KEYFIRST and DB_KEYLAST don't require an exact
             * match, and we don't want to walk multiple pages here
             * to find an undeleted record.  This is handled in the
             * __bam_c_search() routine.
             */
            BT_STK_ENTER(cp, h, base, lock, ret);
            return (ret);
        }

        /*
         * If it's not a leaf page, record the internal page (which is
         * a parent page for the key).  Decrement the base by 1 if it's
         * non-zero so that if a split later occurs, the inserted page
         * will be to the right of the saved page.
         */
        indx = base > 0 ? base - O_INDX : base;

        /*
         * If we're trying to calculate the record number, sum up
         * all the record numbers on this page up to the indx point.
         */
        if (recnop != NULL)
            for (i = 0; i < indx; ++i)
                recno += GET_BINTERNAL(h, i)->nrecs;

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

            if ((ret =
                __bam_lget(dbc, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
                goto err;
        } else {
            /*
             * Decide if we want to return a reference to the next
             * page in the return stack.  If so, 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)memp_fput(dbp->mpf, h, 0);

            if ((ret =
                __bam_lget(dbc, 1, pg, stack && LF_ISSET(S_WRITE) ?
                DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
                goto err;
        }
        if ((ret = memp_fget(dbp->mpf, &pg, 0, &h)) != 0)
            goto err;
    }
    /* NOTREACHED */

match:  *exactp = 1;

    /*
     * If we're trying to calculate the record number, add in the
     * offset on this page and correct for the fact that records
     * in the tree are 0-based.
     */
    if (recnop != NULL)
        *recnop = recno + (indx / P_INDX) + 1;

    /*
     * If we got here, we know that we have a btree leaf page.
     *
     * If there are duplicates, go to the first/last one.  This is
     * safe because we know that we're not going to leave the page,
     * all duplicate sets that are not on overflow pages exist on a
     * single leaf page.
     */
    if (LF_ISSET(S_DUPLAST))
        while (indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
            h->inp[indx] == h->inp[indx + P_INDX])
            indx += P_INDX;
    else
        while (indx > 0 &&
            h->inp[indx] == h->inp[indx - P_INDX])
            indx -= P_INDX;

    /*
     * Now check if we are allowed to return deleted items; if not
     * find the next (or previous) non-deleted item.
     */
    if (LF_ISSET(S_DELNO)) {
        if (LF_ISSET(S_DUPLAST))
            while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
                indx > 0 &&
                h->inp[indx] == h->inp[indx - P_INDX])
                indx -= P_INDX;
        else
            while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
                indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
                h->inp[indx] == h->inp[indx + P_INDX])
                indx += P_INDX;

        if (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type))
            goto notfound;
    }

    BT_STK_ENTER(cp, h, indx, lock, ret);
    return (ret);

notfound:
    (void)memp_fput(dbp->mpf, h, 0);
    (void)__BT_LPUT(dbc, lock);
    ret = DB_NOTFOUND;

err:    if (cp->csp > cp->sp) {
        BT_STK_POP(cp);
        __bam_stkrel(dbc, 0);
    }
    return (ret);
}

/*
 * __bam_stkrel --
 *  Release all pages currently held in the stack.
 *
 * PUBLIC: int __bam_stkrel __P((DBC *, int));
 */
int
__bam_stkrel(dbc, nolocks)
    DBC *dbc;
    int nolocks;
{
    CURSOR *cp;
    DB *dbp;
    EPG *epg;

    dbp = dbc->dbp;
    cp = dbc->internal;

    /* Release inner pages first. */
    for (epg = cp->sp; epg <= cp->csp; ++epg) {
        if (epg->page != NULL)
            (void)memp_fput(dbp->mpf, epg->page, 0);
        if (epg->lock != LOCK_INVALID)
            if (nolocks)
                (void)__BT_LPUT(dbc, epg->lock);
            else
                (void)__BT_TLPUT(dbc, epg->lock);
    }

    /* Clear the stack, all pages have been released. */
    BT_STK_CLR(cp);

    return (0);
}

/*
 * __bam_stkgrow --
 *  Grow the stack.
 *
 * PUBLIC: int __bam_stkgrow __P((CURSOR *));
 */
int
__bam_stkgrow(cp)
    CURSOR *cp;
{
    EPG *p;
    size_t entries;
    int ret;

    entries = cp->esp - cp->sp;

    if ((ret = __os_calloc(entries * 2, sizeof(EPG), &p)) != 0)
        return (ret);
    memcpy(p, cp->sp, entries * sizeof(EPG));
    if (cp->sp != cp->stack)
        __os_free(cp->sp, entries * sizeof(EPG));
    cp->sp = p;
    cp->csp = p + entries;
    cp->esp = p + entries * 2;
    return (0);
}