Class: Sequel::SQL::BooleanExpression

Inherits:

ComplexExpression

• Object
• Expression
• ComplexExpression
• Sequel::SQL::BooleanExpression

Includes:

BooleanMethods

Defined in:

lib/sequel_core/sql.rb

Overview

Subclass of ComplexExpression where the expression results in a boolean value in SQL.

Constant Summary

Constants inherited from ComplexExpression

ComplexExpression::BOOLEAN_OPERATOR_METHODS, ComplexExpression::INEQUALITY_OPERATORS, ComplexExpression::MATHEMATICAL_OPERATORS, ComplexExpression::N_ARITY_OPERATORS, ComplexExpression::ONE_ARITY_OPERATORS, ComplexExpression::OPERTATOR_INVERSIONS, ComplexExpression::TWO_ARITY_OPERATORS

Constants included from ColumnMethods

ColumnMethods::AS, ColumnMethods::ASC, ColumnMethods::DESC

Instance Attribute Summary

Attributes inherited from ComplexExpression

#args, #op

Class Method Summary

• .from_value_pairs(pairs, op = :AND, negate = false) ⇒ Object

  Take pairs of values (e.g. a hash or array of arrays of two pairs) and converts it to a ComplexExpression.

• .invert(ce) ⇒ Object

  Invert the expression, if possible.

Methods included from BooleanMethods

#~

Methods inherited from ComplexExpression

#initialize, #to_s

Methods inherited from Expression

#lit

Methods included from ColumnMethods

#as, #asc, #cast_as, #desc

Constructor Details

This class inherits a constructor from Sequel::SQL::ComplexExpression

Class Method Details

.from_value_pairs(pairs, op = :AND, negate = false) ⇒ Object

Take pairs of values (e.g. a hash or array of arrays of two pairs) and converts it to a ComplexExpression. The operator and args used depends on the case of the right (2nd) argument:

• 0..10 - left >= 0 AND left <= 10

• 1,2

  • left IN (1,2)

• nil - left IS NULL

• /as/ - left ~ ‘as’

• :blah - left = blah

• ‘blah’ - left = ‘blah’

If multiple arguments are given, they are joined with the op given (AND by default, OR possible). If negate is set to true, all subexpressions are inverted before used. Therefore, the following expressions are equivalent:

~from_value_pairs(hash)
from_value_pairs(hash, :OR, true)

# File 'lib/sequel_core/sql.rb', line 342

def self.from_value_pairs(pairs, op=:AND, negate=false)
  pairs = pairs.collect do |l,r|
    ce = case r
    when Range
      new(:AND, new(:>=, l, r.begin), new(r.exclude_end? ? :< : :<=, l, r.end))
    when Array, ::Sequel::Dataset
      new(:IN, l, r)
    when NilClass
      new(:IS, l, r)
    when Regexp
      StringExpression.like(l, r)
    else
      new(:'=', l, r)
    end
    negate ? invert(ce) : ce
  end
  pairs.length == 1 ? pairs.at(0) : new(op, *pairs)
end

.invert(ce) ⇒ Object

Invert the expression, if possible. If the expression cannot be inverted, raise an error. An inverted expression should match everything that the uninverted expression did not match, and vice-versa.

# File 'lib/sequel_core/sql.rb', line 364

def self.invert(ce)
  case ce
  when BooleanExpression
    case op = ce.op
    when :AND, :OR
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.collect{|a| BooleanExpression.invert(a)})
    else
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
    end
  when ComplexExpression
    raise(Sequel::Error, "operator #{ce.op} cannot be inverted")
  else
    BooleanExpression.new(:NOT, ce)
  end
end