# Xapian::Query Class Reference

Class representing a query. More...

`#include <query.h>`

Collaboration diagram for Xapian::Query:

[legend]
List of all members.

## Public Types

enum | op { OP_AND, OP_OR, OP_AND_NOT, OP_XOR, OP_AND_MAYBE, OP_FILTER, OP_NEAR, OP_PHRASE, OP_ELITE_SET = 10 }
| Enum of possible query operations. More...

## Public Member Functions

| Query (const Query &copyme)
| Copy constructor.
Query & | operator= (const Query &copyme)
| Assignment.
| Query ()
| Default constructor: makes an empty query which matches no documents.
| ~Query ()
| Destructor.
| Query (const std::string &tname_, Xapian::termcount wqf_=1, Xapian::termpos pos_=0)
| A query consisting of a single term.
| Query (Query::op op_, const Query &left, const Query &right)
| A query consisting of two subqueries, opp-ed together.
| Query (Query::op op_, const std::string &left, const std::string &right)
| A query consisting of two termnames opp-ed together.
template<class Iterator> | Query (Query::op op_, Iterator qbegin, Iterator qend, Xapian::termcount parameter=0)
| Combine a number of Xapian::Query-s with the specified operator.
| Query (Query::op op_, Xapian::Query q)
| Apply the specified operator to a single Xapian::Query object.
Xapian::termcount | get_length () const
| Get the length of the query, used by some ranking formulae.
TermIterator | get_terms_begin () const
| Return a Xapian::TermIterator returning all the terms in the query, in order of termpos.
TermIterator | get_terms_end () const
| Return a Xapian::TermIterator to the end of the list of terms in the query.
bool | empty () const
| Test is the query is empty (i.e.
bool | is_empty () const
| Deprecated alias for empty().
std::string | get_description () const
| Returns a string representing the query.

## Public Attributes

Xapian::Internal::RefCntPtr< Internal > | internal
| Reference counted internals.

## Detailed Description

Class representing a query.

Queries are represented as a tree of objects.

## Member Enumeration Documentation

enum Xapian::Query::op

Enum of possible query operations.

Enumeration values:

  OP_AND | Return iff both subqueries are satisfied.
  OP_OR | Return if either subquery is satisfied.
  OP_AND_NOT | Return if left but not right satisfied.
  OP_XOR | Return if one query satisfied, but not both.
  OP_AND_MAYBE | Return iff left satisfied, but use weights from both.
  OP_FILTER | As AND, but use only weights from left subquery.
  OP_NEAR | Find occurrences of a list of terms with all the terms occurring within a specified window of positions. Each occurrence of a term must be at a different position, but the order they appear in is irrelevant. The window parameter should be specified for this operation, but will default to the number of terms in the list.
  OP_PHRASE | Find occurrences of a list of terms with all the terms occurring within a specified window of positions, and all the terms appearing in the order specified. Each occurrence of a term must be at a different position. The window parameter should be specified for this operation, but will default to the number of terms in the list.
  OP_ELITE_SET | Select an elite set from the subqueries, and perform a query with these combined as an OR query.

## Constructor & Destructor Documentation

Xapian::Query::Query | ( | const Query & | copyme | ) |

| Copy constructor.

Xapian::Query::Query | ( |  | ) |

| Default constructor: makes an empty query which matches no documents. Also useful for defining a Query object to be assigned to later. An exception will be thrown if an attempt is made to use an undefined query when building up a composite query.

Xapian::Query::~Query | ( |  | ) |

| Destructor.

Xapian::Query::Query | ( | const std::string & | tname_,
|  | Xapian::termcount | wqf_ = `1`,
|  | Xapian::termpos | pos_ = `0`
| ) |

| A query consisting of a single term.

Xapian::Query::Query | ( | Query::op | op_,
|  | const Query & | left,
|  | const Query & | right
| ) |

| A query consisting of two subqueries, opp-ed together.

Xapian::Query::Query | ( | Query::op | op_,
|  | const std::string & | left,
|  | const std::string & | right
| ) |

| A query consisting of two termnames opp-ed together.

template<class Iterator>
Xapian::Query::Query | ( | Query::op | op_,
|  | Iterator | qbegin,
|  | Iterator | qend,
|  | Xapian::termcount | parameter = `0`
| ) |

Combine a number of Xapian::Query-s with the specified operator.

The Xapian::Query objects are specified with begin and end iterators.

AND, OR, NEAR and PHRASE can take any number of subqueries. Other operators take exactly two subqueries.

The iterators may be to Xapian::Query objects, pointers to Xapian::Query objects, or termnames (std::string-s).

For NEAR and PHRASE, a window size can be specified in parameter.

For ELITE_SET, the elite set size can be specified in parameter.

Xapian::Query::Query | ( | Query::op | op_,
|  | Xapian::Query | q
| ) |

| Apply the specified operator to a single Xapian::Query object.

## Member Function Documentation

bool Xapian::Query::empty | ( |  | ) | const

| Test is the query is empty (i.e. was constructed using the default ctor or with an empty iterator ctor).

std::string Xapian::Query::get_description | ( |  | ) | const

| Returns a string representing the query. Introspection method.

Xapian::termcount Xapian::Query::get_length | ( |  | ) | const

| Get the length of the query, used by some ranking formulae. This value is calculated automatically - if you want to override it you can pass a different value to Enquire::set_query().

TermIterator Xapian::Query::get_terms_begin | ( |  | ) | const

| Return a Xapian::TermIterator returning all the terms in the query, in order of termpos. If multiple terms have the same term position, their order is unspecified. Duplicates (same term and termpos) will be removed.

TermIterator Xapian::Query::get_terms_end | ( |  | ) | const`[inline]`

| Return a Xapian::TermIterator to the end of the list of terms in the query.

bool Xapian::Query::is_empty | ( |  | ) | const`[inline]`

| Deprecated alias for empty().

Query& Xapian::Query::operator= | ( | const Query & | copyme | ) |

| Assignment.

## Member Data Documentation

Xapian::Internal::RefCntPtr<Internal> Xapian::Query::internal

| Reference counted internals.

The documentation for this class was generated from the following file:

- include/xapian/query.h