lcn_query.h

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/* Copyright 2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file lcn_query.h
 * @brief Routines for working with queries
 */

#ifndef _LCN_QUERY_H
#define _LCN_QUERY_H

#include "lcn_types.h"
#include "lcn_scorer.h"
#include "lcn_term.h"

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/** Abstract query object. */
typedef struct lcn_query_t lcn_query_t;

/** Create a @a query that matches @a term, allocated in @a pool. */
lcn_error_t *
lcn_term_query_create (lcn_query_t **query,
                       lcn_term_t *term,
                       apr_pool_t *pool);

/** Create a @a query that matches a number of other queries, each of which
 * either MUST occur, SHOULD occur, or MUST NOT occur in the documents matched,
 * the query is allocated in @a pool.
 */
lcn_error_t *
lcn_boolean_query_create (lcn_query_t **query, apr_pool_t *pool);

/** An indication of what requirement is placed on a particular part of a
 * boolean query.
 */
typedef enum {
  LCN_MUST,    /**< The query must match */
  LCN_SHOULD,  /**< At least one of the queries with this occur must match */
  LCN_MUST_NOT /**< The query must not match */
} lcn_boolean_clause_occur_t;

/** Add @a clause to @a query, with @a occur as the specification for whether
 * it is required or not.
 *
 * @note all clauses that are added to @a query must be allocated from a pool
 * that lives at least as long as the pool used to allocate @a query, or the
 * behavior is undefined.
 */
lcn_error_t *
lcn_boolean_query_add (lcn_query_t *query,
                       lcn_query_t *clause,
                       lcn_boolean_clause_occur_t occur);

/** Return @a weight's underlying query. */
lcn_query_t * lcn_weight_query (lcn_weight_t *weight);

/** Return the value of @a weight. */
float lcn_weight_value (lcn_weight_t *weight);

#if NOTYET
/** Return the sum of the squared weight sof contained query clauses. */
lcn_error_t *
lcn_weight_sum_of_squared_weights (float *sum, lcn_weight_t *weight);

/** Assign a query normalization factor @a norm to this @a weight. */
lcn_error_t * lcn_weight_normalize (lcn_weight_t *weight, float norm);

/* XXX leaving out lcn_weight_explain for now... */
#endif

/** Create an @a weight from @a query. */
lcn_error_t *
lcn_query_weight (lcn_weight_t **weight,
                  lcn_query_t *query,
                  apr_pool_t *pool);

/** Return a @a scorer for @a weight run over @a index, allocated in
 * @a pool.
 *
 * @note the Java Lucene version of this stuff works on a Weight, not a
 * Query, but that's mainly because you are supposed to be able to reuse
 * a Query, so we can make that split later.
 */
lcn_error_t *
lcn_weight_scorer (lcn_scorer_t **scorer,
                   lcn_weight_t *weight,
                   lcn_index_t *index,
                   apr_pool_t *pool);

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* _LCN_QUERY_H */

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