NAME

Text::Query::BuildSQL - Base class for SQL query builders

SYNOPSIS

package Text::Query::BuildSQLsqldb;

use Text::Query::BuildSQL;

use vars qw(@ISA);

@ISA = qw(Text::Query::BuildSQL);

DESCRIPTION

Defines all the build_* functions to build a syntax tree. The tree nodes are [ operator scope operand operand... ]. The build_final_expression function translate the syntax tree in a where clause using the resolve method. If the scope of the search is not specified (simple query or advanced query without scope operator), the scope is set to the list of comma separated fields provided by the -fields_searched option. The resulting where clause is placed in the select order provided with the -select option, if any.

SYNTAX TREE

The string enclosed in single quotes must match exactly. The <string> token stands for an arbitrary string. A description enclosed in [something ...] means repeated 0 or N times.

expr: 'or' scope expr [expr ...]
      'and' scope expr [expr ...]
      'not' scope expr
      'near' scope expr_literal expr_literal
      'forbiden' scope expr_literal [expr_literal ...]
      'mandatory' scope expr_literal [expr_literal ...]
      'optional' scope expr_literal [expr_literal ...]
      'literal' scope <string>

expr_literal: literal scope <string>

scope: <string>

METHODS

resolve([], Q1)

Returns a where clause string corresponding to the Q1 syntax tree.

sortplusminus([], Q1)

Translate the mandatory and forbiden syntactic nodes to their boolean equivalents. If it has_relevance returns false and there is at least one mandatory word, the first mandatory word is added to the list of optional words.

has_relevance()

Returns true if relevance ranking is possible, false if not. It is used by the sortplusminus function. Returns false by default.

If relevance ranking is not possible, the semantic of the simple search is slighthly modified. When asking for +a b c it shows all the documents containing a and (b or c).

The normal behaviour is to return all the documents containing a and to sort them to show first those containing (b or c). When relevance ranking is not available the b, c search terms are therefore useless. That is why we decided to change the semantic of the query if no relevance ranking is available.

OPTIONS

-select STRING

If provided the string returned by build_final_expression substitutes the __WHERE__ tag with the where string generated by the resolve function. The substituted string is the return value of the build_final_expression.

If not set the return value of the build_final_expression is the result of the resolve function.

-fields_searched FIELDS_LIST

FIELDS_LIST is a list of comma separated field names. It is used as the default scope if no scope is provided in the query string. The build_final_expression function will croak if this option is not provided and no scope operator were used.

SEE ALSO

Text::Query(3) Text::Query::Build(3)

AUTHORS

Loic Dachary (loic@senga.org)