db_overflow.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: db_overflow.c,v 12.3 2005/08/08 17:30:51 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/db_am.h"
#include "dbinc/mp.h"

/*
 * Big key/data code.
 *
 * Big key and data entries are stored on linked lists of pages.  The initial
 * reference is a structure with the total length of the item and the page
 * number where it begins.  Each entry in the linked list contains a pointer
 * to the next page of data, and so on.
 */

/*
 * __db_goff --
 *      Get an offpage item.
 *
 * PUBLIC: int __db_goff __P((DB *, DBT *,
 * PUBLIC:     u_int32_t, db_pgno_t, void **, u_int32_t *));
 */
int
__db_goff(dbp, dbt, tlen, pgno, bpp, bpsz)
        DB *dbp;
        DBT *dbt;
        u_int32_t tlen;
        db_pgno_t pgno;
        void **bpp;
        u_int32_t *bpsz;
{
        DB_ENV *dbenv;
        DB_MPOOLFILE *mpf;
        PAGE *h;
        db_indx_t bytes;
        u_int32_t curoff, needed, start;
        u_int8_t *p, *src;
        int ret;

        dbenv = dbp->dbenv;
        mpf = dbp->mpf;

        /*
         * Check if the buffer is big enough; if it is not and we are
         * allowed to malloc space, then we'll malloc it.  If we are
         * not (DB_DBT_USERMEM), then we'll set the dbt and return
         * appropriately.
         */
        if (F_ISSET(dbt, DB_DBT_PARTIAL)) {
                start = dbt->doff;
                if (start > tlen)
                        needed = 0;
                else if (dbt->dlen > tlen - start)
                        needed = tlen - start;
                else
                        needed = dbt->dlen;
        } else {
                start = 0;
                needed = tlen;
        }

        /* Allocate any necessary memory. */
        if (F_ISSET(dbt, DB_DBT_USERMEM)) {
                if (needed > dbt->ulen) {
                        dbt->size = needed;
                        return (DB_BUFFER_SMALL);
                }
        } else if (F_ISSET(dbt, DB_DBT_MALLOC)) {
                if ((ret = __os_umalloc(dbenv, needed, &dbt->data)) != 0)
                        return (ret);
        } else if (F_ISSET(dbt, DB_DBT_REALLOC)) {
                if ((ret = __os_urealloc(dbenv, needed, &dbt->data)) != 0)
                        return (ret);
        } else if (bpsz != NULL && (*bpsz == 0 || *bpsz < needed)) {
                if ((ret = __os_realloc(dbenv, needed, bpp)) != 0)
                        return (ret);
                *bpsz = needed;
                dbt->data = *bpp;
        } else if (bpp != NULL)
                dbt->data = *bpp;
        else {
                DB_ASSERT(
                    F_ISSET(dbt,
                    DB_DBT_USERMEM | DB_DBT_MALLOC | DB_DBT_REALLOC) ||
                    bpsz != NULL || bpp != NULL);
                return (DB_BUFFER_SMALL);
        }

        /*
         * Step through the linked list of pages, copying the data on each
         * one into the buffer.  Never copy more than the total data length.
         */
        dbt->size = needed;
        for (curoff = 0, p = dbt->data; pgno != PGNO_INVALID && needed > 0;) {
                if ((ret = __memp_fget(mpf, &pgno, 0, &h)) != 0)
                        return (ret);

                /* Check if we need any bytes from this page. */
                if (curoff + OV_LEN(h) >= start) {
                        src = (u_int8_t *)h + P_OVERHEAD(dbp);
                        bytes = OV_LEN(h);
                        if (start > curoff) {
                                src += start - curoff;
                                bytes -= start - curoff;
                        }
                        if (bytes > needed)
                                bytes = needed;
                        memcpy(p, src, bytes);
                        p += bytes;
                        needed -= bytes;
                }
                curoff += OV_LEN(h);
                pgno = h->next_pgno;
                (void)__memp_fput(mpf, h, 0);
        }
        return (0);
}

/*
 * __db_poff --
 *      Put an offpage item.
 *
 * PUBLIC: int __db_poff __P((DBC *, const DBT *, db_pgno_t *));
 */
int
__db_poff(dbc, dbt, pgnop)
        DBC *dbc;
        const DBT *dbt;
        db_pgno_t *pgnop;
{
        DB *dbp;
        DBT tmp_dbt;
        DB_LSN new_lsn, null_lsn;
        DB_MPOOLFILE *mpf;
        PAGE *pagep, *lastp;
        db_indx_t pagespace;
        u_int32_t sz;
        u_int8_t *p;
        int ret, t_ret;

        /*
         * Allocate pages and copy the key/data item into them.  Calculate the
         * number of bytes we get for pages we fill completely with a single
         * item.
         */
        dbp = dbc->dbp;
        mpf = dbp->mpf;
        pagespace = P_MAXSPACE(dbp, dbp->pgsize);

        ret = 0;
        lastp = NULL;
        for (p = dbt->data,
            sz = dbt->size; sz > 0; p += pagespace, sz -= pagespace) {
                /*
                 * Reduce pagespace so we terminate the loop correctly and
                 * don't copy too much data.
                 */
                if (sz < pagespace)
                        pagespace = sz;

                /*
                 * Allocate and initialize a new page and copy all or part of
                 * the item onto the page.  If sz is less than pagespace, we
                 * have a partial record.
                 */
                if ((ret = __db_new(dbc, P_OVERFLOW, &pagep)) != 0)
                        break;
                if (DBC_LOGGING(dbc)) {
                        tmp_dbt.data = p;
                        tmp_dbt.size = pagespace;
                        ZERO_LSN(null_lsn);
                        if ((ret = __db_big_log(dbp, dbc->txn,
                            &new_lsn, 0, DB_ADD_BIG, PGNO(pagep),
                            lastp ? PGNO(lastp) : PGNO_INVALID,
                            PGNO_INVALID, &tmp_dbt, &LSN(pagep),
                            lastp == NULL ? &null_lsn : &LSN(lastp),
                            &null_lsn)) != 0) {
                                if (lastp != NULL)
                                        (void)__memp_fput(mpf,
                                            lastp, DB_MPOOL_DIRTY);
                                lastp = pagep;
                                break;
                        }
                } else
                        LSN_NOT_LOGGED(new_lsn);

                /* Move LSN onto page. */
                if (lastp != NULL)
                        LSN(lastp) = new_lsn;
                LSN(pagep) = new_lsn;

                OV_LEN(pagep) = pagespace;
                OV_REF(pagep) = 1;
                memcpy((u_int8_t *)pagep + P_OVERHEAD(dbp), p, pagespace);

                /*
                 * If this is the first entry, update the user's info.
                 * Otherwise, update the entry on the last page filled
                 * in and release that page.
                 */
                if (lastp == NULL)
                        *pgnop = PGNO(pagep);
                else {
                        lastp->next_pgno = PGNO(pagep);
                        pagep->prev_pgno = PGNO(lastp);
                        (void)__memp_fput(mpf, lastp, DB_MPOOL_DIRTY);
                }
                lastp = pagep;
        }
        if (lastp != NULL &&
            (t_ret = __memp_fput(mpf, lastp, DB_MPOOL_DIRTY)) != 0 && ret == 0)
                ret = t_ret;
        return (ret);
}

/*
 * __db_ovref --
 *      Increment/decrement the reference count on an overflow page.
 *
 * PUBLIC: int __db_ovref __P((DBC *, db_pgno_t, int32_t));
 */
int
__db_ovref(dbc, pgno, adjust)
        DBC *dbc;
        db_pgno_t pgno;
        int32_t adjust;
{
        DB *dbp;
        DB_MPOOLFILE *mpf;
        PAGE *h;
        int ret;

        dbp = dbc->dbp;
        mpf = dbp->mpf;

        if ((ret = __memp_fget(mpf, &pgno, 0, &h)) != 0)
                return (ret);

        if (DBC_LOGGING(dbc)) {
                if ((ret = __db_ovref_log(dbp,
                    dbc->txn, &LSN(h), 0, h->pgno, adjust, &LSN(h))) != 0) {
                        (void)__memp_fput(mpf, h, 0);
                        return (ret);
                }
        } else
                LSN_NOT_LOGGED(LSN(h));
        OV_REF(h) += adjust;

        (void)__memp_fput(mpf, h, DB_MPOOL_DIRTY);
        return (0);
}

/*
 * __db_doff --
 *      Delete an offpage chain of overflow pages.
 *
 * PUBLIC: int __db_doff __P((DBC *, db_pgno_t));
 */
int
__db_doff(dbc, pgno)
        DBC *dbc;
        db_pgno_t pgno;
{
        DB *dbp;
        PAGE *pagep;
        DB_LSN null_lsn;
        DB_MPOOLFILE *mpf;
        DBT tmp_dbt;
        int ret;

        dbp = dbc->dbp;
        mpf = dbp->mpf;

        do {
                if ((ret = __memp_fget(mpf, &pgno, 0, &pagep)) != 0)
                        return (ret);

                DB_ASSERT(TYPE(pagep) == P_OVERFLOW);
                /*
                 * If it's referenced by more than one key/data item,
                 * decrement the reference count and return.
                 */
                if (OV_REF(pagep) > 1) {
                        (void)__memp_fput(mpf, pagep, 0);
                        return (__db_ovref(dbc, pgno, -1));
                }

                if (DBC_LOGGING(dbc)) {
                        tmp_dbt.data = (u_int8_t *)pagep + P_OVERHEAD(dbp);
                        tmp_dbt.size = OV_LEN(pagep);
                        ZERO_LSN(null_lsn);
                        if ((ret = __db_big_log(dbp, dbc->txn,
                            &LSN(pagep), 0, DB_REM_BIG,
                            PGNO(pagep), PREV_PGNO(pagep),
                            NEXT_PGNO(pagep), &tmp_dbt,
                            &LSN(pagep), &null_lsn, &null_lsn)) != 0) {
                                (void)__memp_fput(mpf, pagep, 0);
                                return (ret);
                        }
                } else
                        LSN_NOT_LOGGED(LSN(pagep));
                pgno = pagep->next_pgno;
                OV_LEN(pagep) = 0;
                if ((ret = __db_free(dbc, pagep)) != 0)
                        return (ret);
        } while (pgno != PGNO_INVALID);

        return (0);
}

/*
 * __db_moff --
 *      Match on overflow pages.
 *
 * Given a starting page number and a key, return <0, 0, >0 to indicate if the
 * key on the page is less than, equal to or greater than the key specified.
 * We optimize this by doing chunk at a time comparison unless the user has
 * specified a comparison function.  In this case, we need to materialize
 * the entire object and call their comparison routine.
 *
 * PUBLIC: int __db_moff __P((DB *, const DBT *, db_pgno_t, u_int32_t,
 * PUBLIC:     int (*)(DB *, const DBT *, const DBT *), int *));
 */
int
__db_moff(dbp, dbt, pgno, tlen, cmpfunc, cmpp)
        DB *dbp;
        const DBT *dbt;
        db_pgno_t pgno;
        u_int32_t tlen;
        int (*cmpfunc) __P((DB *, const DBT *, const DBT *)), *cmpp;
{
        DBT local_dbt;
        DB_MPOOLFILE *mpf;
        PAGE *pagep;
        void *buf;
        u_int32_t bufsize, cmp_bytes, key_left;
        u_int8_t *p1, *p2;
        int ret;

        mpf = dbp->mpf;

        /*
         * If there is a user-specified comparison function, build a
         * contiguous copy of the key, and call it.
         */
        if (cmpfunc != NULL) {
                memset(&local_dbt, 0, sizeof(local_dbt));
                buf = NULL;
                bufsize = 0;

                if ((ret = __db_goff(dbp,
                    &local_dbt, tlen, pgno, &buf, &bufsize)) != 0)
                        return (ret);
                /* Pass the key as the first argument */
                *cmpp = cmpfunc(dbp, dbt, &local_dbt);
                __os_free(dbp->dbenv, buf);
                return (0);
        }

        /* While there are both keys to compare. */
        for (*cmpp = 0, p1 = dbt->data,
            key_left = dbt->size; key_left > 0 && pgno != PGNO_INVALID;) {
                if ((ret = __memp_fget(mpf, &pgno, 0, &pagep)) != 0)
                        return (ret);

                cmp_bytes = OV_LEN(pagep) < key_left ? OV_LEN(pagep) : key_left;
                tlen -= cmp_bytes;
                key_left -= cmp_bytes;
                for (p2 = (u_int8_t *)pagep + P_OVERHEAD(dbp);
                    cmp_bytes-- > 0; ++p1, ++p2)
                        if (*p1 != *p2) {
                                *cmpp = (long)*p1 - (long)*p2;
                                break;
                        }
                pgno = NEXT_PGNO(pagep);
                if ((ret = __memp_fput(mpf, pagep, 0)) != 0)
                        return (ret);
                if (*cmpp != 0)
                        return (0);
        }
        if (key_left > 0)               /* DBT is longer than the page key. */
                *cmpp = 1;
        else if (tlen > 0)              /* DBT is shorter than the page key. */
                *cmpp = -1;
        else
                *cmpp = 0;

        return (0);
}

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