bt_recno.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: bt_recno.c,v 12.6 2005/08/08 14:27:59 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/btree.h"
#include "dbinc/db_shash.h"
#include "dbinc/lock.h"

static int  __ram_add __P((DBC *, db_recno_t *, DBT *, u_int32_t, u_int32_t));
static int  __ram_source __P((DB *));
static int  __ram_sread __P((DBC *, db_recno_t));
static int  __ram_update __P((DBC *, db_recno_t, int));

/*
 * In recno, there are two meanings to the on-page "deleted" flag.  If we're
 * re-numbering records, it means the record was implicitly created.  We skip
 * over implicitly created records if doing a cursor "next" or "prev", and
 * return DB_KEYEMPTY if they're explicitly requested..  If not re-numbering
 * records, it means that the record was implicitly created, or was deleted.
 * We skip over implicitly created or deleted records if doing a cursor "next"
 * or "prev", and return DB_KEYEMPTY if they're explicitly requested.
 *
 * If we're re-numbering records, then we have to detect in the cursor that
 * a record was deleted, and adjust the cursor as necessary on the next get.
 * If we're not re-numbering records, then we can detect that a record has
 * been deleted by looking at the actual on-page record, so we completely
 * ignore the cursor's delete flag.  This is different from the B+tree code.
 * It also maintains whether the cursor references a deleted record in the
 * cursor, and it doesn't always check the on-page value.
 */
#define CD_SET(cp) {                                                    \
        if (F_ISSET(cp, C_RENUMBER))                                    \
                F_SET(cp, C_DELETED);                                   \
}
#define CD_CLR(cp) {                                                    \
        if (F_ISSET(cp, C_RENUMBER)) {                                  \
                F_CLR(cp, C_DELETED);                                   \
                cp->order = INVALID_ORDER;                              \
        }                                                               \
}
#define CD_ISSET(cp)                                                    \
        (F_ISSET(cp, C_RENUMBER) && F_ISSET(cp, C_DELETED) ? 1 : 0)

/*
 * Macros for comparing the ordering of two cursors.
 * cp1 comes before cp2 iff one of the following holds:
 *      cp1's recno is less than cp2's recno
 *      recnos are equal, both deleted, and cp1's order is less than cp2's
 *      recnos are equal, cp1 deleted, and cp2 not deleted
 */
#define C_LESSTHAN(cp1, cp2)                                            \
    (((cp1)->recno < (cp2)->recno) ||                                   \
    (((cp1)->recno == (cp2)->recno) &&                                  \
    ((CD_ISSET((cp1)) && CD_ISSET((cp2)) && (cp1)->order < (cp2)->order) || \
    (CD_ISSET((cp1)) && !CD_ISSET((cp2))))))

/*
 * cp1 is equal to cp2 iff their recnos and delete flags are identical,
 * and if the delete flag is set their orders are also identical.
 */
#define C_EQUAL(cp1, cp2)                                               \
    ((cp1)->recno == (cp2)->recno && CD_ISSET((cp1)) == CD_ISSET((cp2)) && \
    (!CD_ISSET((cp1)) || (cp1)->order == (cp2)->order))

/*
 * Do we need to log the current cursor adjustment?
 */
#define CURADJ_LOG(dbc)                                                 \
        (DBC_LOGGING((dbc)) && (dbc)->txn != NULL && (dbc)->txn->parent != NULL)

/*
 * After a search, copy the found page into the cursor, discarding any
 * currently held lock.
 */
#define STACK_TO_CURSOR(cp, ret) {                                      \
        int __t_ret;                                                    \
        (cp)->page = (cp)->csp->page;                                   \
        (cp)->pgno = (cp)->csp->page->pgno;                             \
        (cp)->indx = (cp)->csp->indx;                                   \
        if ((__t_ret = __TLPUT(dbc, (cp)->lock)) != 0 && (ret) == 0)    \
                ret = __t_ret;                                          \
        (cp)->lock = (cp)->csp->lock;                                   \
        (cp)->lock_mode = (cp)->csp->lock_mode;                         \
}

/*
 * __ram_open --
 *      Recno open function.
 *
 * PUBLIC: int __ram_open __P((DB *,
 * PUBLIC:      DB_TXN *, const char *, db_pgno_t, u_int32_t));
 */
int
__ram_open(dbp, txn, name, base_pgno, flags)
        DB *dbp;
        DB_TXN *txn;
        const char *name;
        db_pgno_t base_pgno;
        u_int32_t flags;
{
        BTREE *t;
        DBC *dbc;
        int ret, t_ret;

        COMPQUIET(name, NULL);
        t = dbp->bt_internal;

        /* Start up the tree. */
        if ((ret = __bam_read_root(dbp, txn, base_pgno, flags)) != 0)
                return (ret);

        /*
         * If the user specified a source tree, open it and map it in.
         *
         * !!!
         * We don't complain if the user specified transactions or threads.
         * It's possible to make it work, but you'd better know what you're
         * doing!
         */
        if (t->re_source != NULL && (ret = __ram_source(dbp)) != 0)
                return (ret);

        /* If we're snapshotting an underlying source file, do it now. */
        if (F_ISSET(dbp, DB_AM_SNAPSHOT)) {
                /* Allocate a cursor. */
                if ((ret = __db_cursor(dbp, NULL, &dbc, 0)) != 0)
                        return (ret);

                /* Do the snapshot. */
                if ((ret = __ram_update(dbc,
                    DB_MAX_RECORDS, 0)) != 0 && ret == DB_NOTFOUND)
                        ret = 0;

                /* Discard the cursor. */
                if ((t_ret = __db_c_close(dbc)) != 0 && ret == 0)
                        ret = t_ret;
        }

        return (ret);
}

/*
 * __ram_append --
 *      Recno append function.
 *
 * PUBLIC: int __ram_append __P((DBC *, DBT *, DBT *));
 */
int
__ram_append(dbc, key, data)
        DBC *dbc;
        DBT *key, *data;
{
        BTREE_CURSOR *cp;
        int ret;

        cp = (BTREE_CURSOR *)dbc->internal;

        /*
         * Make sure we've read in all of the backing source file.  If
         * we found the record or it simply didn't exist, add the
         * user's record.
         */
        ret = __ram_update(dbc, DB_MAX_RECORDS, 0);
        if (ret == 0 || ret == DB_NOTFOUND)
                ret = __ram_add(dbc, &cp->recno, data, DB_APPEND, 0);

        /* Return the record number. */
        if (ret == 0)
                ret = __db_retcopy(dbc->dbp->dbenv, key, &cp->recno,
                    sizeof(cp->recno), &dbc->rkey->data, &dbc->rkey->ulen);

        return (ret);
}

/*
 * __ram_c_del --
 *      Recno cursor->c_del function.
 *
 * PUBLIC: int __ram_c_del __P((DBC *));
 */
int
__ram_c_del(dbc)
        DBC *dbc;
{
        BKEYDATA bk;
        BTREE *t;
        BTREE_CURSOR *cp;
        DB *dbp;
        DB_LSN lsn;
        DBT hdr, data;
        int exact, ret, stack, t_ret;

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;
        t = dbp->bt_internal;
        stack = 0;

        /*
         * The semantics of cursors during delete are as follows: in
         * non-renumbering recnos, records are replaced with a marker
         * containing a delete flag.  If the record referenced by this cursor
         * has already been deleted, we will detect that as part of the delete
         * operation, and fail.
         *
         * In renumbering recnos, cursors which represent deleted items
         * are flagged with the C_DELETED flag, and it is an error to
         * call c_del a second time without an intervening cursor motion.
         */
        if (CD_ISSET(cp))
                return (DB_KEYEMPTY);

        /* Search the tree for the key; delete only deletes exact matches. */
        if ((ret = __bam_rsearch(dbc, &cp->recno, S_DELETE, 1, &exact)) != 0)
                goto err;
        if (!exact) {
                ret = DB_NOTFOUND;
                goto err;
        }
        stack = 1;

        /* Copy the page into the cursor. */
        STACK_TO_CURSOR(cp, ret);
        if (ret != 0)
                goto err;

        /*
         * If re-numbering records, the on-page deleted flag can only mean
         * that this record was implicitly created.  Applications aren't
         * permitted to delete records they never created, return an error.
         *
         * If not re-numbering records, the on-page deleted flag means that
         * this record was implicitly created, or, was deleted at some time.
         * The former is an error because applications aren't permitted to
         * delete records they never created, the latter is an error because
         * if the record was "deleted", we could never have found it.
         */
        if (B_DISSET(GET_BKEYDATA(dbp, cp->page, cp->indx)->type)) {
                ret = DB_KEYEMPTY;
                goto err;
        }

        if (F_ISSET(cp, C_RENUMBER)) {
                /* Delete the item, adjust the counts, adjust the cursors. */
                if ((ret = __bam_ditem(dbc, cp->page, cp->indx)) != 0)
                        goto err;
                if ((ret = __bam_adjust(dbc, -1)) != 0)
                        goto err;
                if (__ram_ca(dbc, CA_DELETE) > 0 &&
                    CURADJ_LOG(dbc) && (ret = __bam_rcuradj_log(dbp, dbc->txn,
                    &lsn, 0, CA_DELETE, cp->root, cp->recno, cp->order)) != 0)
                        goto err;

                /*
                 * If the page is empty, delete it.
                 *
                 * We never delete a root page.  First, root pages of primary
                 * databases never go away, recno or otherwise.  However, if
                 * it's the root page of an off-page duplicates database, then
                 * it can be deleted.   We don't delete it here because we have
                 * no way of telling the primary database page holder (e.g.,
                 * the hash access method) that its page element should cleaned
                 * up because the underlying tree is gone.  So, we keep the page
                 * around until the last cursor referencing the empty tree is
                 * are closed, and then clean it up.
                 */
                if (NUM_ENT(cp->page) == 0 && PGNO(cp->page) != cp->root) {
                        /*
                         * We want to delete a single item out of the last page
                         * that we're not deleting.
                         */
                        ret = __bam_dpages(dbc, 0, 0);

                        /*
                         * Regardless of the return from __bam_dpages, it will
                         * discard our stack and pinned page.
                         */
                        stack = 0;
                        cp->page = NULL;
                }
        } else {
                /* Use a delete/put pair to replace the record with a marker. */
                if ((ret = __bam_ditem(dbc, cp->page, cp->indx)) != 0)
                        goto err;

                B_TSET(bk.type, B_KEYDATA, 1);
                bk.len = 0;
                memset(&hdr, 0, sizeof(hdr));
                hdr.data = &bk;
                hdr.size = SSZA(BKEYDATA, data);
                memset(&data, 0, sizeof(data));
                data.data = (void *)"";
                data.size = 0;
                if ((ret = __db_pitem(dbc,
                    cp->page, cp->indx, BKEYDATA_SIZE(0), &hdr, &data)) != 0)
                        goto err;
        }

        t->re_modified = 1;

err:    if (stack && (t_ret = __bam_stkrel(dbc, STK_CLRDBC)) != 0 && ret == 0)
                ret = t_ret;

        return (ret);
}

/*
 * __ram_c_get --
 *      Recno cursor->c_get function.
 *
 * PUBLIC: int __ram_c_get
 * PUBLIC:     __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
 */
int
__ram_c_get(dbc, key, data, flags, pgnop)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
        db_pgno_t *pgnop;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        int cmp, exact, ret;

        COMPQUIET(pgnop, NULL);

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

        LF_CLR(DB_MULTIPLE|DB_MULTIPLE_KEY);
retry:  switch (flags) {
        case DB_CURRENT:
                /*
                 * If we're using mutable records and the deleted flag is
                 * set, the cursor is pointing at a nonexistent record;
                 * return an error.
                 */
                if (CD_ISSET(cp))
                        return (DB_KEYEMPTY);
                break;
        case DB_NEXT_DUP:
                /*
                 * If we're not in an off-page dup set, we know there's no
                 * next duplicate since recnos don't have them.  If we
                 * are in an off-page dup set, the next item assuredly is
                 * a dup, so we set flags to DB_NEXT and keep going.
                 */
                if (!F_ISSET(dbc, DBC_OPD))
                        return (DB_NOTFOUND);
                /* FALLTHROUGH */
        case DB_NEXT_NODUP:
                /*
                 * Recno databases don't have duplicates, set flags to DB_NEXT
                 * and keep going.
                 */
                /* FALLTHROUGH */
        case DB_NEXT:
                flags = DB_NEXT;
                /*
                 * If record numbers are mutable: if we just deleted a record,
                 * we have to avoid incrementing the record number so that we
                 * return the right record by virtue of renumbering the tree.
                 */
                if (CD_ISSET(cp)) {
                        /*
                         * Clear the flag, we've moved off the deleted record.
                         */
                        CD_CLR(cp);
                        break;
                }

                if (cp->recno != RECNO_OOB) {
                        ++cp->recno;
                        break;
                }
                /* FALLTHROUGH */
        case DB_FIRST:
                flags = DB_NEXT;
                cp->recno = 1;
                break;
        case DB_PREV_NODUP:
                /*
                 * Recno databases don't have duplicates, set flags to DB_PREV
                 * and keep going.
                 */
                /* FALLTHROUGH */
        case DB_PREV:
                flags = DB_PREV;
                if (cp->recno != RECNO_OOB) {
                        if (cp->recno == 1) {
                                ret = DB_NOTFOUND;
                                goto err;
                        }
                        --cp->recno;
                        break;
                }
                /* FALLTHROUGH */
        case DB_LAST:
                flags = DB_PREV;
                if (((ret = __ram_update(dbc,
                    DB_MAX_RECORDS, 0)) != 0) && ret != DB_NOTFOUND)
                        goto err;
                if ((ret = __bam_nrecs(dbc, &cp->recno)) != 0)
                        goto err;
                if (cp->recno == 0) {
                        ret = DB_NOTFOUND;
                        goto err;
                }
                break;
        case DB_GET_BOTHC:
                /*
                 * If we're doing a join and these are offpage dups,
                 * we want to keep searching forward from after the
                 * current cursor position.  Increment the recno by 1,
                 * then proceed as for a DB_SET.
                 *
                 * Otherwise, we know there are no additional matching
                 * data, as recnos don't have dups.  return DB_NOTFOUND.
                 */
                if (F_ISSET(dbc, DBC_OPD)) {
                        cp->recno++;
                        break;
                }
                ret = DB_NOTFOUND;
                goto err;
                /* NOTREACHED */
        case DB_GET_BOTH:
        case DB_GET_BOTH_RANGE:
                /*
                 * If we're searching a set of off-page dups, we start
                 * a new linear search from the first record.  Otherwise,
                 * we compare the single data item associated with the
                 * requested record for a match.
                 */
                if (F_ISSET(dbc, DBC_OPD)) {
                        cp->recno = 1;
                        break;
                }
                /* FALLTHROUGH */
        case DB_SET:
        case DB_SET_RANGE:
                if ((ret = __ram_getno(dbc, key, &cp->recno, 0)) != 0)
                        goto err;
                break;
        default:
                ret = __db_unknown_flag(dbp->dbenv, "__ram_c_get", flags);
                goto err;
        }

        /*
         * For DB_PREV, DB_LAST, DB_SET and DB_SET_RANGE, we have already
         * called __ram_update() to make sure sufficient records have been
         * read from the backing source file.  Do it now for DB_CURRENT (if
         * the current record was deleted we may need more records from the
         * backing file for a DB_CURRENT operation), DB_FIRST and DB_NEXT.
         * (We don't have to test for flags == DB_FIRST, because the switch
         * statement above re-set flags to DB_NEXT in that case.)
         */
        if ((flags == DB_NEXT || flags == DB_CURRENT) && ((ret =
            __ram_update(dbc, cp->recno, 0)) != 0) && ret != DB_NOTFOUND)
                goto err;

        for (;; ++cp->recno) {
                /* Search the tree for the record. */
                if ((ret = __bam_rsearch(dbc, &cp->recno,
                    F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND,
                    1, &exact)) != 0)
                        goto err;
                if (!exact) {
                        ret = DB_NOTFOUND;
                        goto err;
                }

                /* Copy the page into the cursor. */
                STACK_TO_CURSOR(cp, ret);
                if (ret != 0)
                        goto err;

                /*
                 * If re-numbering records, the on-page deleted flag means this
                 * record was implicitly created.  If not re-numbering records,
                 * the on-page deleted flag means this record was implicitly
                 * created, or, it was deleted at some time.  Regardless, we
                 * skip such records if doing cursor next/prev operations or
                 * walking through off-page duplicates, and fail if they were
                 * requested explicitly by the application.
                 */
                if (B_DISSET(GET_BKEYDATA(dbp, cp->page, cp->indx)->type))
                        switch (flags) {
                        case DB_NEXT:
                        case DB_PREV:
                                (void)__bam_stkrel(dbc, STK_CLRDBC);
                                goto retry;
                        case DB_GET_BOTH:
                        case DB_GET_BOTH_RANGE:
                                /*
                                 * If we're an OPD tree, we don't care about
                                 * matching a record number on a DB_GET_BOTH
                                 * -- everything belongs to the same tree.  A
                                 * normal recno should give up and return
                                 * DB_NOTFOUND if the matching recno is deleted.
                                 */
                                if (F_ISSET(dbc, DBC_OPD)) {
                                        (void)__bam_stkrel(dbc, STK_CLRDBC);
                                        continue;
                                }
                                ret = DB_NOTFOUND;
                                goto err;
                        default:
                                ret = DB_KEYEMPTY;
                                goto err;
                        }

                if (flags == DB_GET_BOTH ||
                    flags == DB_GET_BOTHC || flags == DB_GET_BOTH_RANGE) {
                        if ((ret = __bam_cmp(dbp, data,
                            cp->page, cp->indx, __bam_defcmp, &cmp)) != 0)
                                return (ret);
                        if (cmp == 0)
                                break;
                        if (!F_ISSET(dbc, DBC_OPD)) {
                                ret = DB_NOTFOUND;
                                goto err;
                        }
                        (void)__bam_stkrel(dbc, STK_CLRDBC);
                } else
                        break;
        }

        /* Return the key if the user didn't give us one. */
        if (!F_ISSET(dbc, DBC_OPD)) {
                if (flags != DB_GET_BOTH && flags != DB_GET_BOTH_RANGE &&
                    flags != DB_SET && flags != DB_SET_RANGE)
                        ret = __db_retcopy(dbp->dbenv,
                            key, &cp->recno, sizeof(cp->recno),
                            &dbc->rkey->data, &dbc->rkey->ulen);
                F_SET(key, DB_DBT_ISSET);
        }

        /* The cursor was reset, no further delete adjustment is necessary. */
err:    CD_CLR(cp);

        return (ret);
}

/*
 * __ram_c_put --
 *      Recno cursor->c_put function.
 *
 * PUBLIC: int __ram_c_put __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
 */
int
__ram_c_put(dbc, key, data, flags, pgnop)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
        db_pgno_t *pgnop;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        DB_LSN lsn;
        int exact, nc, ret, t_ret;
        u_int32_t iiflags;
        void *arg;

        COMPQUIET(pgnop, NULL);

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

        /*
         * DB_KEYFIRST and DB_KEYLAST mean different things if they're
         * used in an off-page duplicate tree.  If we're an off-page
         * duplicate tree, they really mean "put at the beginning of the
         * tree" and "put at the end of the tree" respectively, so translate
         * them to something else.
         */
        if (F_ISSET(dbc, DBC_OPD))
                switch (flags) {
                case DB_KEYFIRST:
                        cp->recno = 1;
                        flags = DB_BEFORE;
                        break;
                case DB_KEYLAST:
                        if ((ret = __ram_add(dbc,
                            &cp->recno, data, DB_APPEND, 0)) != 0)
                                return (ret);
                        if (CURADJ_LOG(dbc) &&
                            (ret = __bam_rcuradj_log(dbp, dbc->txn, &lsn, 0,
                            CA_ICURRENT, cp->root, cp->recno, cp->order)) != 0)
                                return (ret);
                        return (0);
                default:
                        break;
                }

        /*
         * Handle normal DB_KEYFIRST/DB_KEYLAST;  for a recno, which has
         * no duplicates, these are identical and mean "put the given
         * datum at the given recno".
         *
         * Note that the code here used to be in __ram_put;  now, we
         * go through the access-method-common __db_put function, which
         * handles DB_NOOVERWRITE, so we and __ram_add don't have to.
         */
        if (flags == DB_KEYFIRST || flags == DB_KEYLAST) {
                ret = __ram_getno(dbc, key, &cp->recno, 1);
                if (ret == 0 || ret == DB_NOTFOUND)
                        ret = __ram_add(dbc, &cp->recno, data, 0, 0);
                return (ret);
        }

        /*
         * If we're putting with a cursor that's marked C_DELETED, we need to
         * take special care;  the cursor doesn't "really" reference the item
         * corresponding to its current recno, but instead is "between" that
         * record and the current one.  Translate the actual insert into
         * DB_BEFORE, and let the __ram_ca work out the gory details of what
         * should wind up pointing where.
         */
        if (CD_ISSET(cp))
                iiflags = DB_BEFORE;
        else
                iiflags = flags;

split:  if ((ret = __bam_rsearch(dbc, &cp->recno, S_INSERT, 1, &exact)) != 0)
                goto err;
        /*
         * An inexact match is okay;  it just means we're one record past the
         * end, which is reasonable if we're marked deleted.
         */
        DB_ASSERT(exact || CD_ISSET(cp));

        /* Copy the page into the cursor. */
        STACK_TO_CURSOR(cp, ret);
        if (ret != 0)
                goto err;

        ret = __bam_iitem(dbc, key, data, iiflags, 0);
        t_ret = __bam_stkrel(dbc, STK_CLRDBC);

        if (t_ret != 0 && (ret == 0 || ret == DB_NEEDSPLIT))
                ret = t_ret;
        else if (ret == DB_NEEDSPLIT) {
                arg = &cp->recno;
                if ((ret = __bam_split(dbc, arg, NULL)) != 0)
                        goto err;
                goto split;
        }
        if (ret != 0)
                goto err;

        switch (flags) {                        /* Adjust the cursors. */
        case DB_AFTER:
                nc = __ram_ca(dbc, CA_IAFTER);

                /*
                 * We only need to adjust this cursor forward if we truly added
                 * the item after the current recno, rather than remapping it
                 * to DB_BEFORE.
                 */
                if (iiflags == DB_AFTER)
                        ++cp->recno;

                /* Only log if __ram_ca found any relevant cursors. */
                if (nc > 0 && CURADJ_LOG(dbc) &&
                    (ret = __bam_rcuradj_log(dbp, dbc->txn, &lsn, 0, CA_IAFTER,
                    cp->root, cp->recno, cp->order)) != 0)
                        goto err;
                break;
        case DB_BEFORE:
                nc = __ram_ca(dbc, CA_IBEFORE);
                --cp->recno;

                /* Only log if __ram_ca found any relevant cursors. */
                if (nc > 0 && CURADJ_LOG(dbc) &&
                    (ret = __bam_rcuradj_log(dbp, dbc->txn, &lsn, 0, CA_IBEFORE,
                    cp->root, cp->recno, cp->order)) != 0)
                        goto err;
                break;
        case DB_CURRENT:
                /*
                 * We only need to do an adjustment if we actually
                 * added an item, which we only would have done if the
                 * cursor was marked deleted.
                 *
                 * Only log if __ram_ca found any relevant cursors.
                 */
                if (CD_ISSET(cp) && __ram_ca(dbc, CA_ICURRENT) > 0 &&
                    CURADJ_LOG(dbc) &&
                    (ret = __bam_rcuradj_log(dbp, dbc->txn, &lsn, 0,
                    CA_ICURRENT, cp->root, cp->recno, cp->order)) != 0)
                        goto err;
                break;
        default:
                break;
        }

        /* Return the key if we've created a new record. */
        if (!F_ISSET(dbc, DBC_OPD) && (flags == DB_AFTER || flags == DB_BEFORE))
                ret = __db_retcopy(dbp->dbenv, key, &cp->recno,
                    sizeof(cp->recno), &dbc->rkey->data, &dbc->rkey->ulen);

        /* The cursor was reset, no further delete adjustment is necessary. */
err:    CD_CLR(cp);

        return (ret);
}

/*
 * __ram_ca --
 *      Adjust cursors.  Returns the number of relevant cursors.
 *
 * PUBLIC: int __ram_ca __P((DBC *, ca_recno_arg));
 */
int
__ram_ca(dbc_arg, op)
        DBC *dbc_arg;
        ca_recno_arg op;
{
        BTREE_CURSOR *cp, *cp_arg;
        DB *dbp, *ldbp;
        DB_ENV *dbenv;
        DBC *dbc;
        db_recno_t recno;
        int adjusted, found;
        u_int32_t order;

        dbp = dbc_arg->dbp;
        dbenv = dbp->dbenv;
        cp_arg = (BTREE_CURSOR *)dbc_arg->internal;
        recno = cp_arg->recno;

        found = 0;

        /*
         * It only makes sense to adjust cursors if we're a renumbering
         * recno;  we should only be called if this is one.
         */
        DB_ASSERT(F_ISSET(cp_arg, C_RENUMBER));

        MUTEX_LOCK(dbenv, dbenv->mtx_dblist);
        /*
         * Adjust the cursors.  See the comment in __bam_ca_delete().
         */
        /*
         * If we're doing a delete, we need to find the highest
         * order of any cursor currently pointing at this item,
         * so we can assign a higher order to the newly deleted
         * cursor.  Unfortunately, this requires a second pass through
         * the cursor list.
         */
        if (op == CA_DELETE) {
                order = 1;
                for (ldbp = __dblist_get(dbenv, dbp->adj_fileid);
                    ldbp != NULL && ldbp->adj_fileid == dbp->adj_fileid;
                    ldbp = LIST_NEXT(ldbp, dblistlinks)) {
                        MUTEX_LOCK(dbenv, dbp->mutex);
                        for (dbc = TAILQ_FIRST(&ldbp->active_queue);
                            dbc != NULL; dbc = TAILQ_NEXT(dbc, links)) {
                                cp = (BTREE_CURSOR *)dbc->internal;
                                if (cp_arg->root == cp->root &&
                                    recno == cp->recno && CD_ISSET(cp) &&
                                    order <= cp->order)
                                        order = cp->order + 1;
                        }
                        MUTEX_UNLOCK(dbenv, dbp->mutex);
                }
        } else
                order = INVALID_ORDER;

        /* Now go through and do the actual adjustments. */
        for (ldbp = __dblist_get(dbenv, dbp->adj_fileid);
            ldbp != NULL && ldbp->adj_fileid == dbp->adj_fileid;
            ldbp = LIST_NEXT(ldbp, dblistlinks)) {
                MUTEX_LOCK(dbenv, dbp->mutex);
                for (dbc = TAILQ_FIRST(&ldbp->active_queue);
                    dbc != NULL; dbc = TAILQ_NEXT(dbc, links)) {
                        cp = (BTREE_CURSOR *)dbc->internal;
                        if (cp_arg->root != cp->root)
                                continue;
                        ++found;
                        adjusted = 0;
                        switch (op) {
                        case CA_DELETE:
                                if (recno < cp->recno) {
                                        --cp->recno;
                                        /*
                                         * If the adjustment made them equal,
                                         * we have to merge the orders.
                                         */
                                        if (recno == cp->recno && CD_ISSET(cp))
                                                cp->order += order;
                                } else if (recno == cp->recno &&
                                    !CD_ISSET(cp)) {
                                        CD_SET(cp);
                                        cp->order = order;
                                }
                                break;
                        case CA_IBEFORE:
                                /*
                                 * IBEFORE is just like IAFTER, except that we
                                 * adjust cursors on the current record too.
                                 */
                                if (C_EQUAL(cp_arg, cp)) {
                                        ++cp->recno;
                                        adjusted = 1;
                                }
                                goto iafter;
                        case CA_ICURRENT:

                                /*
                                 * If the original cursor wasn't deleted, we
                                 * just did a replacement and so there's no
                                 * need to adjust anything--we shouldn't have
                                 * gotten this far.  Otherwise, we behave
                                 * much like an IAFTER, except that all
                                 * cursors pointing to the current item get
                                 * marked undeleted and point to the new
                                 * item.
                                 */
                                DB_ASSERT(CD_ISSET(cp_arg));
                                if (C_EQUAL(cp_arg, cp)) {
                                        CD_CLR(cp);
                                        break;
                                }
                                /* FALLTHROUGH */
                        case CA_IAFTER:
iafter:                         if (!adjusted && C_LESSTHAN(cp_arg, cp)) {
                                        ++cp->recno;
                                        adjusted = 1;
                                }
                                if (recno == cp->recno && adjusted)
                                        /*
                                         * If we've moved this cursor's recno,
                                         * split its order number--i.e.,
                                         * decrement it by enough so that
                                         * the lowest cursor moved has order 1.
                                         * cp_arg->order is the split point,
                                         * so decrement by one less than that.
                                         */
                                        cp->order -= (cp_arg->order - 1);
                                break;
                        }
                }
                MUTEX_UNLOCK(dbp->dbenv, dbp->mutex);
        }
        MUTEX_UNLOCK(dbenv, dbenv->mtx_dblist);

        return (found);
}

/*
 * __ram_getno --
 *      Check the user's record number, and make sure we've seen it.
 *
 * PUBLIC: int __ram_getno __P((DBC *, const DBT *, db_recno_t *, int));
 */
int
__ram_getno(dbc, key, rep, can_create)
        DBC *dbc;
        const DBT *key;
        db_recno_t *rep;
        int can_create;
{
        DB *dbp;
        db_recno_t recno;

        dbp = dbc->dbp;

        /* Check the user's record number. */
        if ((recno = *(db_recno_t *)key->data) == 0) {
                __db_err(dbp->dbenv, "illegal record number of 0");
                return (EINVAL);
        }
        if (rep != NULL)
                *rep = recno;

        /*
         * Btree can neither create records nor read them in.  Recno can
         * do both, see if we can find the record.
         */
        return (dbc->dbtype == DB_RECNO ?
            __ram_update(dbc, recno, can_create) : 0);
}

/*
 * __ram_update --
 *      Ensure the tree has records up to and including the specified one.
 */
static int
__ram_update(dbc, recno, can_create)
        DBC *dbc;
        db_recno_t recno;
        int can_create;
{
        BTREE *t;
        DB *dbp;
        DBT *rdata;
        db_recno_t nrecs;
        int ret;

        dbp = dbc->dbp;
        t = dbp->bt_internal;

        /*
         * If we can't create records and we've read the entire backing input
         * file, we're done.
         */
        if (!can_create && t->re_eof)
                return (0);

        /*
         * If we haven't seen this record yet, try to get it from the original
         * file.
         */
        if ((ret = __bam_nrecs(dbc, &nrecs)) != 0)
                return (ret);
        if (!t->re_eof && recno > nrecs) {
                if ((ret = __ram_sread(dbc, recno)) != 0 && ret != DB_NOTFOUND)
                        return (ret);
                if ((ret = __bam_nrecs(dbc, &nrecs)) != 0)
                        return (ret);
        }

        /*
         * If we can create records, create empty ones up to the requested
         * record.
         */
        if (!can_create || recno <= nrecs + 1)
                return (0);

        rdata = &dbc->my_rdata;
        rdata->flags = 0;
        rdata->size = 0;

        while (recno > ++nrecs)
                if ((ret = __ram_add(dbc,
                    &nrecs, rdata, 0, BI_DELETED)) != 0)
                        return (ret);
        return (0);
}

/*
 * __ram_source --
 *      Load information about the backing file.
 */
static int
__ram_source(dbp)
        DB *dbp;
{
        BTREE *t;
        char *source;
        int ret;

        t = dbp->bt_internal;

        /* Find the real name, and swap out the one we had before. */
        if ((ret = __db_appname(dbp->dbenv,
            DB_APP_DATA, t->re_source, 0, NULL, &source)) != 0)
                return (ret);
        __os_free(dbp->dbenv, t->re_source);
        t->re_source = source;

        /*
         * !!!
         * It's possible that the backing source file is read-only.  We don't
         * much care other than we'll complain if there are any modifications
         * when it comes time to write the database back to the source.
         */
        if ((t->re_fp = fopen(t->re_source, "r")) == NULL) {
                ret = __os_get_errno();
                __db_err(dbp->dbenv, "%s: %s", t->re_source, db_strerror(ret));
                return (ret);
        }

        t->re_eof = 0;
        return (0);
}

/*
 * __ram_writeback --
 *      Rewrite the backing file.
 *
 * PUBLIC: int __ram_writeback __P((DB *));
 */
int
__ram_writeback(dbp)
        DB *dbp;
{
        BTREE *t;
        DB_ENV *dbenv;
        DBC *dbc;
        DBT key, data;
        FILE *fp;
        db_recno_t keyno;
        int ret, t_ret;
        u_int8_t delim, *pad;

        t = dbp->bt_internal;
        dbenv = dbp->dbenv;
        fp = NULL;
        pad = NULL;

        /* If the file wasn't modified, we're done. */
        if (!t->re_modified)
                return (0);

        /* If there's no backing source file, we're done. */
        if (t->re_source == NULL) {
                t->re_modified = 0;
                return (0);
        }

        /*
         * We step through the records, writing each one out.  Use the record
         * number and the dbp->get() function, instead of a cursor, so we find
         * and write out "deleted" or non-existent records.  The DB handle may
         * be threaded, so allocate memory as we go.
         */
        memset(&key, 0, sizeof(key));
        key.size = sizeof(db_recno_t);
        key.data = &keyno;
        memset(&data, 0, sizeof(data));
        F_SET(&data, DB_DBT_REALLOC);

        /* Allocate a cursor. */
        if ((ret = __db_cursor(dbp, NULL, &dbc, 0)) != 0)
                return (ret);

        /*
         * Read any remaining records into the tree.
         *
         * !!!
         * This is why we can't support transactions when applications specify
         * backing (re_source) files.  At this point we have to read in the
         * rest of the records from the file so that we can write all of the
         * records back out again, which could modify a page for which we'd
         * have to log changes and which we don't have locked.  This could be
         * partially fixed by taking a snapshot of the entire file during the
         * DB->open as DB->open is transaction protected.  But, if a checkpoint
         * occurs then, the part of the log holding the copy of the file could
         * be discarded, and that would make it impossible to recover in the
         * face of disaster.  This could all probably be fixed, but it would
         * require transaction protecting the backing source file.
         *
         * XXX
         * This could be made to work now that we have transactions protecting
         * file operations.  Margo has specifically asked for the privilege of
         * doing this work.
         */
        if ((ret =
            __ram_update(dbc, DB_MAX_RECORDS, 0)) != 0 && ret != DB_NOTFOUND)
                goto err;

        /*
         * Close any existing file handle and re-open the file, truncating it.
         */
        if (t->re_fp != NULL) {
                if (fclose(t->re_fp) != 0) {
                        ret = __os_get_errno();
                        goto err;
                }
                t->re_fp = NULL;
        }
        if ((fp = fopen(t->re_source, "w")) == NULL) {
                ret = __os_get_errno();
                __db_err(dbenv, "%s: %s", t->re_source, db_strerror(ret));
                goto err;
        }

        /*
         * We'll need the delimiter if we're doing variable-length records,
         * and the pad character if we're doing fixed-length records.
         */
        delim = t->re_delim;
        for (keyno = 1;; ++keyno) {
                switch (ret = __db_get(dbp, NULL, &key, &data, 0)) {
                case 0:
                        if (data.size != 0 &&
                            fwrite(data.data, 1, data.size, fp) != data.size)
                                goto write_err;
                        break;
                case DB_KEYEMPTY:
                        if (F_ISSET(dbp, DB_AM_FIXEDLEN)) {
                                if (pad == NULL) {
                                        if ((ret = __os_malloc(
                                            dbenv, t->re_len, &pad)) != 0)
                                                goto err;
                                        memset(pad, t->re_pad, t->re_len);
                                }
                                if (fwrite(pad, 1, t->re_len, fp) != t->re_len)
                                        goto write_err;
                        }
                        break;
                case DB_NOTFOUND:
                        ret = 0;
                        goto done;
                default:
                        goto err;
                }
                if (!F_ISSET(dbp, DB_AM_FIXEDLEN) &&
                    fwrite(&delim, 1, 1, fp) != 1) {
write_err:              ret = __os_get_errno();
                        __db_err(dbenv,
                            "%s: write failed to backing file: %s",
                            t->re_source, strerror(ret));
                        goto err;
                }
        }

err:
done:   /* Close the file descriptor. */
        if (fp != NULL && fclose(fp) != 0) {
                t_ret = __os_get_errno();
                if (ret == 0)
                        ret = t_ret;
                __db_err(dbenv, "%s: %s", t->re_source, db_strerror(t_ret));
        }

        /* Discard the cursor. */
        if ((t_ret = __db_c_close(dbc)) != 0 && ret == 0)
                ret = t_ret;

        /* Discard memory allocated to hold the data items. */
        if (data.data != NULL)
                __os_ufree(dbenv, data.data);
        if (pad != NULL)
                __os_free(dbenv, pad);

        if (ret == 0)
                t->re_modified = 0;

        return (ret);
}

/*
 * __ram_sread --
 *      Read records from a source file.
 */
static int
__ram_sread(dbc, top)
        DBC *dbc;
        db_recno_t top;
{
        BTREE *t;
        DB *dbp;
        DBT data, *rdata;
        db_recno_t recno;
        size_t len;
        int ch, ret, was_modified;

        t = dbc->dbp->bt_internal;
        dbp = dbc->dbp;
        was_modified = t->re_modified;

        if ((ret = __bam_nrecs(dbc, &recno)) != 0)
                return (ret);

        /*
         * Use the record key return memory, it's only a short-term use.
         * The record data return memory is used by __bam_iitem, which
         * we'll indirectly call, so use the key so as not to collide.
         */
        len = F_ISSET(dbp, DB_AM_FIXEDLEN) ? t->re_len : 256;
        rdata = &dbc->my_rkey;
        if (rdata->ulen < len) {
                if ((ret = __os_realloc(
                    dbp->dbenv, len, &rdata->data)) != 0) {
                        rdata->ulen = 0;
                        rdata->data = NULL;
                        return (ret);
                }
                rdata->ulen = (u_int32_t)len;
        }

        memset(&data, 0, sizeof(data));
        while (recno < top) {
                data.data = rdata->data;
                data.size = 0;
                if (F_ISSET(dbp, DB_AM_FIXEDLEN))
                        for (len = t->re_len; len > 0; --len) {
                                if ((ch = getc(t->re_fp)) == EOF) {
                                        if (data.size == 0)
                                                goto eof;
                                        break;
                                }
                                ((u_int8_t *)data.data)[data.size++] = ch;
                        }
                else
                        for (;;) {
                                if ((ch = getc(t->re_fp)) == EOF) {
                                        if (data.size == 0)
                                                goto eof;
                                        break;
                                }
                                if (ch == t->re_delim)
                                        break;

                                ((u_int8_t *)data.data)[data.size++] = ch;
                                if (data.size == rdata->ulen) {
                                        if ((ret = __os_realloc(dbp->dbenv,
                                            rdata->ulen *= 2,
                                            &rdata->data)) != 0) {
                                                rdata->ulen = 0;
                                                rdata->data = NULL;
                                                return (ret);
                                        } else
                                                data.data = rdata->data;
                                }
                        }

                /*
                 * Another process may have read this record from the input
                 * file and stored it into the database already, in which
                 * case we don't need to repeat that operation.  We detect
                 * this by checking if the last record we've read is greater
                 * or equal to the number of records in the database.
                 */
                if (t->re_last >= recno) {
                        ++recno;
                        if ((ret = __ram_add(dbc, &recno, &data, 0, 0)) != 0)
                                goto err;
                }
                ++t->re_last;
        }

        if (0) {
eof:            t->re_eof = 1;
                ret = DB_NOTFOUND;
        }
err:    if (!was_modified)
                t->re_modified = 0;

        return (ret);
}

/*
 * __ram_add --
 *      Add records into the tree.
 */
static int
__ram_add(dbc, recnop, data, flags, bi_flags)
        DBC *dbc;
        db_recno_t *recnop;
        DBT *data;
        u_int32_t flags, bi_flags;
{
        BTREE_CURSOR *cp;
        int exact, ret, stack, t_ret;

        cp = (BTREE_CURSOR *)dbc->internal;

retry:  /* Find the slot for insertion. */
        if ((ret = __bam_rsearch(dbc, recnop,
            S_INSERT | (flags == DB_APPEND ? S_APPEND : 0), 1, &exact)) != 0)
                return (ret);
        stack = 1;

        /* Copy the page into the cursor. */
        STACK_TO_CURSOR(cp, ret);
        if (ret != 0)
                goto err;

        /*
         * The application may modify the data based on the selected record
         * number.
         */
        if (flags == DB_APPEND && dbc->dbp->db_append_recno != NULL &&
            (ret = dbc->dbp->db_append_recno(dbc->dbp, data, *recnop)) != 0)
                goto err;

        /*
         * Select the arguments for __bam_iitem() and do the insert.  If the
         * key is an exact match, or we're replacing the data item with a
         * new data item, replace the current item.  If the key isn't an exact
         * match, we're inserting a new key/data pair, before the search
         * location.
         */
        switch (ret = __bam_iitem(dbc,
            NULL, data, exact ? DB_CURRENT : DB_BEFORE, bi_flags)) {
        case 0:
                /*
                 * Don't adjust anything.
                 *
                 * If we inserted a record, no cursors need adjusting because
                 * the only new record it's possible to insert is at the very
                 * end of the tree.  The necessary adjustments to the internal
                 * page counts were made by __bam_iitem().
                 *
                 * If we overwrote a record, no cursors need adjusting because
                 * future DBcursor->get calls will simply return the underlying
                 * record (there's no adjustment made for the DB_CURRENT flag
                 * when a cursor get operation immediately follows a cursor
                 * delete operation, and the normal adjustment for the DB_NEXT
                 * flag is still correct).
                 */
                break;
        case DB_NEEDSPLIT:
                /* Discard the stack of pages and split the page. */
                (void)__bam_stkrel(dbc, STK_CLRDBC);
                stack = 0;

                if ((ret = __bam_split(dbc, recnop, NULL)) != 0)
                        goto err;

                goto retry;
                /* NOTREACHED */
        default:
                goto err;
        }

err:    if (stack && (t_ret = __bam_stkrel(dbc, STK_CLRDBC)) != 0 && ret == 0)
                ret = t_ret;

        return (ret);
}

---