/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1998
 *      Sleepycat Software.  All rights reserved.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)db_join.c     10.10 (Sleepycat) 10/9/98";
#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 "db_join.h"
#include "db_am.h"
#include "common_ext.h"

static int __db_join_close __P((DBC *));
static int __db_join_del __P((DBC *, u_int32_t));
static int __db_join_get __P((DBC *, DBT *, DBT *, u_int32_t));
static int __db_join_put __P((DBC *, DBT *, DBT *, u_int32_t));

/*
 * This is the duplicate-assisted join functionality.  Right now we're
 * going to write it such that we return one item at a time, although
 * I think we may need to optimize it to return them all at once.
 * It should be easier to get it working this way, and I believe that
 * changing it should be fairly straightforward.
 *
 * XXX
 * Right now we do not maintain the number of duplicates so we do
 * not optimize the join.  If the caller does, then best performance
 * will be achieved by putting the cursor with the smallest cardinality
 * first.
 *
 * The first cursor moves sequentially through the duplicate set while
 * the others search explicitly for the duplicate in question.
 *
 */

/*
 * __db_join --
 *      This is the interface to the duplicate-assisted join functionality.
 * In the same way that cursors mark a position in a database, a cursor
 * can mark a position in a join.  While most cursors are created by the
 * cursor method of a DB, join cursors are created through an explicit
 * call to DB->join.
 *
 * The curslist is an array of existing, intialized cursors and primary
 * is the DB of the primary file.  The data item that joins all the
 * cursors in the curslist is used as the key into the primary and that
 * key and data are returned.  When no more items are left in the join
 * set, the  c_next operation off the join cursor will return DB_NOTFOUND.
 *
 * PUBLIC: int __db_join __P((DB *, DBC **, u_int32_t, DBC **));
 */
int
__db_join(primary, curslist, flags, dbcp)
        DB *primary;
        DBC **curslist, **dbcp;
        u_int32_t flags;
{
        DBC *dbc;
        JOIN_CURSOR *jc;
        int i, ret;

        DB_PANIC_CHECK(primary);

        if ((ret = __db_joinchk(primary, flags)) != 0)
                return (ret);

        if (curslist == NULL || curslist[0] == NULL)
                return (EINVAL);

        dbc = NULL;
        jc = NULL;

        if ((ret = __os_calloc(1, sizeof(DBC), &dbc)) != 0)
                goto err;

        if ((ret = __os_calloc(1, sizeof(JOIN_CURSOR), &jc)) != 0)
                goto err;

        if ((ret = __os_malloc(256, NULL, &jc->j_key.data)) != 0)
                goto err;
        jc->j_key.ulen = 256;
        F_SET(&jc->j_key, DB_DBT_USERMEM);

        for (jc->j_curslist = curslist;
            *jc->j_curslist != NULL; jc->j_curslist++)
                ;
        if ((ret = __os_calloc((jc->j_curslist - curslist + 1),
            sizeof(DBC *), &jc->j_curslist)) != 0)
                goto err;
        for (i = 0; curslist[i] != NULL; i++) {
                if (i != 0)
                        F_SET(curslist[i], DBC_KEYSET);
                jc->j_curslist[i] = curslist[i];
        }

        dbc->c_close = __db_join_close;
        dbc->c_del = __db_join_del;
        dbc->c_get = __db_join_get;
        dbc->c_put = __db_join_put;
        dbc->internal = jc;
        dbc->dbp = primary;
        jc->j_init = 1;
        jc->j_primary = primary;

        *dbcp = dbc;

        return (0);

err:    if (jc != NULL) {
                if (jc->j_curslist != NULL)
                        __os_free(jc->j_curslist,
                            (jc->j_curslist - curslist + 1) * sizeof(DBC *));
                __os_free(jc, sizeof(JOIN_CURSOR));
        }
        if (dbc != NULL)
                __os_free(dbc, sizeof(DBC));
        return (ret);
}

static int
__db_join_put(dbc, key, data, flags)
        DBC *dbc;
        DBT *key;
        DBT *data;
        u_int32_t flags;
{
        DB_PANIC_CHECK(dbc->dbp);

        COMPQUIET(key, NULL);
        COMPQUIET(data, NULL);
        COMPQUIET(flags, 0);
        return (EINVAL);
}

static int
__db_join_del(dbc, flags)
        DBC *dbc;
        u_int32_t flags;
{
        DB_PANIC_CHECK(dbc->dbp);

        COMPQUIET(flags, 0);
        return (EINVAL);
}

static int
__db_join_get(dbc, key, data, flags)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
{
        DB *dbp;
        DBC **cpp;
        JOIN_CURSOR *jc;
        int ret;
        u_int32_t operation;

        dbp = dbc->dbp;

        DB_PANIC_CHECK(dbp);

        operation = LF_ISSET(DB_OPFLAGS_MASK);
        if (operation != 0 && operation != DB_JOIN_ITEM)
                return (__db_ferr(dbp->dbenv, "DBcursor->c_get", 0));

        LF_CLR(DB_OPFLAGS_MASK);
        if ((ret =
            __db_fchk(dbp->dbenv, "DBcursor->c_get", flags, DB_RMW)) != 0)
                return (ret);

        jc = (JOIN_CURSOR *)dbc->internal;
retry:
        ret = jc->j_curslist[0]->c_get(jc->j_curslist[0],
            &jc->j_key, key, jc->j_init ? DB_CURRENT : DB_NEXT_DUP);

        if (ret == ENOMEM) {
                jc->j_key.ulen <<= 1;
                if ((ret = __os_realloc(&jc->j_key.data, jc->j_key.ulen)) != 0)
                        return (ret);
                goto retry;
        }
        if (ret != 0)
                return (ret);

        jc->j_init = 0;
        do {
                /*
                 * We have the first element; now look for it in the
                 * other cursors.
                 */
                for (cpp = jc->j_curslist + 1; *cpp != NULL; cpp++) {
retry2:                 if ((ret = ((*cpp)->c_get)(*cpp,
                            &jc->j_key, key, DB_GET_BOTH)) == DB_NOTFOUND)
                                break;
                        if (ret == ENOMEM) {
                                jc->j_key.ulen <<= 1;
                                if ((ret = __os_realloc(&jc->j_key.data,
                                    jc->j_key.ulen)) != 0)
                                        return (ret);
                                goto retry2;
                        }
                        if (F_ISSET(*cpp, DBC_KEYSET)) {
                                F_CLR(*cpp, DBC_KEYSET);
                                F_SET(*cpp, DBC_CONTINUE);
                        }
                }

                /*
                 * If we got out of here with ret != 0, then we failed to
                 * find the duplicate in one of the files, so we go on to
                 * the next item in the outermost relation. If ret was
                 * equal to 0, then we've got something to return.
                 */
                if (ret == 0)
                        break;
        } while ((ret = jc->j_curslist[0]->c_get(jc->j_curslist[0],
            &jc->j_key, key,  DB_NEXT_DUP)) == 0);

        /*
         * If ret != 0 here, we've exhausted the first file.  Otherwise,
         * key and data are set and we need to do the lookup on the
         * primary.
         */
        if (ret != 0)
                return (ret);

        if (operation == DB_JOIN_ITEM)
                return (0);
        else
                return ((jc->j_primary->get)(jc->j_primary,
                    jc->j_curslist[0]->txn, key, data, 0));
}

static int
__db_join_close(dbc)
        DBC *dbc;
{
        JOIN_CURSOR *jc;
        int i;

        DB_PANIC_CHECK(dbc->dbp);

        jc = (JOIN_CURSOR *)dbc->internal;

        /*
         * Clear the optimization flag in the cursors.
         */
        for (i = 0; jc->j_curslist[i] != NULL; i++)
                F_CLR(jc->j_curslist[i], DBC_CONTINUE | DBC_KEYSET);

        __os_free(jc->j_curslist, 0);
        __os_free(jc->j_key.data, jc->j_key.ulen);
        __os_free(jc, sizeof(JOIN_CURSOR));
        __os_free(dbc, sizeof(DBC));

        return (0);
}