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/** @file
* @brief Multi-database support functions
*/
/* Copyright (C) 2017 Olly Betts
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see
* <https://www.gnu.org/licenses/>.
*/
#ifndef XAPIAN_INCLUDED_MULTI_H
#define XAPIAN_INCLUDED_MULTI_H
#include <xapian/types.h>
#include "omassert.h"
/** Convert docid in the multi-db to the docid in the shard.
*
* @param did docid in the multi-db
* @param n_shards number of dbs in the multi-db
*
* @return docid in the shard
*/
inline Xapian::docid
shard_docid(Xapian::docid did, Xapian::doccount n_shards) {
Assert(did != 0);
Assert(n_shards != 0);
return (did - 1) / n_shards + 1;
}
/** Convert docid in the multi-db to shard number.
*
* @param did docid in the multi-db
* @param n_shards number of dbs in the multi-db
*
* @return shard number between 0 and (n_shards - 1) inclusive
*/
inline Xapian::doccount
shard_number(Xapian::docid did, Xapian::doccount n_shards) {
Assert(did != 0);
Assert(n_shards != 0);
return Xapian::doccount((did - 1) % n_shards);
}
/** Convert shard number and shard docid to docid in multi-db.
*
* @param shard_did docid in the shard
* @param shard shard number between 0 and (n_shards - 1) inclusive
* @param n_shards number of dbs in the multi-db
*
* @return docid in the multi-db.
*/
inline Xapian::docid
unshard(Xapian::docid shard_did,
Xapian::doccount shard,
Xapian::doccount n_shards) {
Assert(shard_did != 0);
AssertRel(shard,<,n_shards);
return (shard_did - 1) * n_shards + shard + 1;
}
#endif // XAPIAN_INCLUDED_MULTI_H
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