query.h

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/* Copyright (C) 2011,2012,2013,2014,2015,2016,2017,2018,2019 Olly Betts
 * Copyright (C) 2008 Richard Boulton
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#ifndef XAPIAN_INCLUDED_QUERY_H
#define XAPIAN_INCLUDED_QUERY_H

#if !defined XAPIAN_IN_XAPIAN_H && !defined XAPIAN_LIB_BUILD
# error Never use <xapian/query.h> directly; include <xapian.h> instead.
#endif

#include <string>

#include <xapian/attributes.h>
#include <xapian/intrusive_ptr.h>
#include <xapian/postingiterator.h>
#include <xapian/registry.h>
#include <xapian/termiterator.h>
#include <xapian/types.h>
#include <xapian/visibility.h>

class QueryOptimiser; // FIXME

namespace Xapian {

class PostingSource;

class XAPIAN_VISIBILITY_DEFAULT Query {
  public:
    class Internal;
    Xapian::Internal::intrusive_ptr<Internal> internal;

    static const Xapian::Query MatchNothing;

    static const Xapian::Query MatchAll;

    enum op {
        OP_AND = 0,

        OP_OR = 1,

        OP_AND_NOT = 2,

        OP_XOR = 3,

        OP_AND_MAYBE = 4,

        OP_FILTER = 5,

        OP_NEAR = 6,

        OP_PHRASE = 7,

        OP_VALUE_RANGE = 8,

        OP_SCALE_WEIGHT = 9,

        OP_ELITE_SET = 10,

        OP_VALUE_GE = 11,

        OP_VALUE_LE = 12,

        OP_SYNONYM = 13,

        OP_MAX = 14,

        OP_WILDCARD = 15,

        OP_INVALID = 99,

        LEAF_TERM = 100,

        LEAF_POSTING_SOURCE,

        LEAF_MATCH_ALL,

        LEAF_MATCH_NOTHING
    };

    enum {
        WILDCARD_LIMIT_ERROR,
        WILDCARD_LIMIT_FIRST,
        WILDCARD_LIMIT_MOST_FREQUENT
    };

    XAPIAN_NOTHROW(Query()) { }

    ~Query() { }

    Query(const Query & o) : internal(o.internal) { }

    Query & operator=(const Query & o) { internal = o.internal; return *this; }

#ifdef XAPIAN_MOVE_SEMANTICS
    Query(Query &&) = default;

    Query & operator=(Query &&) = default;
#endif

    Query(const std::string & term,
          Xapian::termcount wqf = 1,
          Xapian::termpos pos = 0);

    explicit Query(Xapian::PostingSource * source);

    Query(double factor, const Xapian::Query & subquery);

    Query(op op_, const Xapian::Query & subquery, double factor);

    Query(op op_, const Xapian::Query & a, const Xapian::Query & b)
    {
        init(op_, 2);
        bool positional = (op_ == OP_NEAR || op_ == OP_PHRASE);
        add_subquery(positional, a);
        add_subquery(positional, b);
        done();
    }

    Query(op op_, const std::string & a, const std::string & b)
    {
        init(op_, 2);
        add_subquery(false, a);
        add_subquery(false, b);
        done();
    }

    Query(op op_, Xapian::valueno slot, const std::string & range_limit);

    Query(op op_, Xapian::valueno slot,
          const std::string & range_lower, const std::string & range_upper);

    Query(op op_,
          const std::string & pattern,
          Xapian::termcount max_expansion = 0,
          int max_type = WILDCARD_LIMIT_ERROR,
          op combiner = OP_SYNONYM);

    template<typename I>
    Query(op op_, I begin, I end, Xapian::termcount window = 0)
    {
        if (begin != end) {
            typedef typename std::iterator_traits<I>::iterator_category iterator_category;
            init(op_, window, begin, end, iterator_category());
            bool positional = (op_ == OP_NEAR || op_ == OP_PHRASE);
            for (I i = begin; i != end; ++i) {
                add_subquery(positional, *i);
            }
            done();
        }
    }

#ifdef SWIG
    // SWIG's %template doesn't seem to handle a templated ctor so we
    // provide this fake specialised form of the above prototype.
    Query(op op_, XapianSWIGQueryItor qbegin, XapianSWIGQueryItor qend,
          Xapian::termcount parameter = 0);

# ifdef SWIGJAVA
    Query(op op_, XapianSWIGStrItor qbegin, XapianSWIGStrItor qend,
          Xapian::termcount parameter = 0);
# endif
#endif

    const TermIterator get_terms_begin() const;

    const TermIterator XAPIAN_NOTHROW(get_terms_end() const) {
        return TermIterator();
    }

    const TermIterator get_unique_terms_begin() const;

    const TermIterator XAPIAN_NOTHROW(get_unique_terms_end() const) {
        return TermIterator();
    }

    Xapian::termcount XAPIAN_NOTHROW(get_length() const) XAPIAN_PURE_FUNCTION;

    bool XAPIAN_NOTHROW(empty() const) {
        return internal.get() == 0;
    }

    std::string serialise() const;

    static const Query unserialise(const std::string & serialised,
                                   const Registry & reg = Registry());

    op XAPIAN_NOTHROW(get_type() const) XAPIAN_PURE_FUNCTION;

    size_t XAPIAN_NOTHROW(get_num_subqueries() const) XAPIAN_PURE_FUNCTION;

    const Query get_subquery(size_t n) const;

    std::string get_description() const;

    const Query operator&=(const Query & o);

    const Query operator|=(const Query & o);

    const Query operator^=(const Query & o);

    const Query operator*=(double factor) {
        return (*this = Query(factor, *this));
    }

    const Query operator/=(double factor) {
        return (*this = Query(1.0 / factor, *this));
    }

    explicit Query(Internal * internal_) : internal(internal_) { }

    explicit Query(Query::op op_) {
        init(op_, 0);
        if (op_ != Query::OP_INVALID) done();
    }

  private:
    void init(Query::op op_, size_t n_subqueries, Xapian::termcount window = 0);

    template<typename I>
    void init(Query::op op_, Xapian::termcount window,
              const I & begin, const I & end, std::random_access_iterator_tag)
    {
        init(op_, end - begin, window);
    }

    template<typename I>
    void init(Query::op op_, Xapian::termcount window,
              const I &, const I &, std::input_iterator_tag)
    {
        init(op_, 0, window);
    }

    void add_subquery(bool positional, const Xapian::Query & subquery);

    void add_subquery(bool, const std::string & subquery) {
        add_subquery(false, Xapian::Query(subquery));
    }

    void add_subquery(bool positional, const Xapian::Query * subquery) {
        // FIXME: subquery NULL?
        add_subquery(positional, *subquery);
    }

    void done();
};

inline const Query
operator&(const Query & a, const Query & b)
{
    return Query(Query::OP_AND, a, b);
}

inline const Query
operator|(const Query & a, const Query & b)
{
    return Query(Query::OP_OR, a, b);
}

inline const Query
operator^(const Query & a, const Query & b)
{
    return Query(Query::OP_XOR, a, b);
}

inline const Query
operator*(double factor, const Query & q)
{
    return Query(factor, q);
}

inline const Query
operator*(const Query & q, double factor)
{
    return Query(factor, q);
}

inline const Query
operator/(const Query & q, double factor)
{
    return Query(1.0 / factor, q);
}

class InvertedQuery_ {
    const Query & query;

    void operator=(const InvertedQuery_ &);

    explicit InvertedQuery_(const Query & query_) : query(query_) { }

  public:
    // GCC 4.2 seems to needs a copy ctor.
    InvertedQuery_(const InvertedQuery_ & o) : query(o.query) { }

    operator Query() const {
        return Query(Query::OP_AND_NOT, Query(std::string()), query);
    }

    friend const InvertedQuery_ operator~(const Query &q);

    friend const Query operator&(const Query & a, const InvertedQuery_ & b);

    friend const Query operator&=(Query & a, const InvertedQuery_ & b);
};

inline const Query
operator&(const Query & a, const InvertedQuery_ & b)
{
    return Query(Query::OP_AND_NOT, a, b.query);
}

inline const Query
operator&=(Query & a, const InvertedQuery_ & b)
{
    return (a = Query(Query::OP_AND_NOT, a, b.query));
}

#ifndef DOXYGEN /* @internal doesn't seem to avoid a warning here. */

inline const InvertedQuery_
operator~(const Query &q)
{
    return InvertedQuery_(q);
}
#endif

namespace Internal {
class AndContext;
class OrContext;
class XorContext;
}

class Query::Internal : public Xapian::Internal::intrusive_base {
  public:
    XAPIAN_NOTHROW(Internal()) { }

    virtual ~Internal();

    virtual PostingIterator::Internal * postlist(QueryOptimiser * qopt, double factor) const = 0;

    virtual void postlist_sub_and_like(Xapian::Internal::AndContext& ctx,
                                       QueryOptimiser * qopt,
                                       double factor) const;

    virtual void postlist_sub_or_like(Xapian::Internal::OrContext& ctx,
                                      QueryOptimiser * qopt,
                                      double factor) const;

    virtual void postlist_sub_xor(Xapian::Internal::XorContext& ctx,
                                  QueryOptimiser * qopt,
                                  double factor) const;

    virtual termcount XAPIAN_NOTHROW(get_length() const) XAPIAN_PURE_FUNCTION;

    virtual void serialise(std::string & result) const = 0;

    static Query::Internal * unserialise(const char ** p, const char * end, const Registry & reg);

    virtual Query::op XAPIAN_NOTHROW(get_type() const) XAPIAN_PURE_FUNCTION = 0;
    virtual size_t XAPIAN_NOTHROW(get_num_subqueries() const) XAPIAN_PURE_FUNCTION;
    virtual const Query get_subquery(size_t n) const;

    virtual std::string get_description() const = 0;

    // Pass argument as void* to avoid need to include <vector>.
    virtual void gather_terms(void * void_terms) const;
};

inline const Query
Query::operator&=(const Query & o)
{
    if (o.empty()) {
        // q &= empty_query sets q to empty_query.
        *this = o;
    } else if (this != &o &&
               internal.get() &&
               internal->_refs == 1 &&
               get_type() == OP_AND) {
        // Appending a subquery to an existing AND.
        add_subquery(false, o);
    } else {
        *this = Query(OP_AND, *this, o);
    }
    return *this;
}

inline const Query
Query::operator|=(const Query & o)
{
    if (o.empty()) {
        // q |= empty_query is a no-op.
    } else if (this != &o &&
               internal.get() &&
               internal->_refs == 1 &&
               get_type() == OP_OR) {
        // Appending a subquery to an existing OR.
        add_subquery(false, o);
    } else {
        *this = Query(OP_OR, *this, o);
    }
    return *this;
}

inline const Query
Query::operator^=(const Query & o)
{
    if (o.empty()) {
        // q ^= empty_query is a no-op.
    } else if (internal.get() == o.internal.get()) {
        // q ^= q gives MatchNothing.
        internal = NULL;
    } else if (internal.get() &&
               internal->_refs == 1 &&
               get_type() == OP_XOR) {
        // Appending a subquery to an existing XOR.
        add_subquery(false, o);
    } else {
        *this = Query(OP_XOR, *this, o);
    }
    return *this;
}

}

#endif // XAPIAN_INCLUDED_QUERY_H