Class: Sequel::SQL::BooleanExpression

Inherits:
ComplexExpression show all
Includes:
BooleanMethods
Defined in:
lib/sequel/lib/sequel/sql.rb

Overview

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

Constant Summary

Constants inherited from ComplexExpression

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

Instance Attribute Summary

Attributes inherited from ComplexExpression

#args, #op

Class Method Summary collapse

Methods included from BooleanMethods

#~

Methods inherited from ComplexExpression

#eql?, #initialize

Methods included from SubscriptMethods

#sql_subscript

Methods included from OrderMethods

#asc, #desc

Methods included from CastMethods

#cast, #cast_numeric, #cast_string

Methods included from AliasMethods

#as

Methods inherited from Expression

#lit

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 BooleanExpression. 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)

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# File 'lib/sequel/lib/sequel/sql.rb', line 424

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, SQLArray
      new(:IN, l, r)
    when NilClass, TrueClass, FalseClass
      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, except for possible issues with SQL NULL (i.e. 1 == NULL is NULL and 1 != NULL is also NULL).


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# File 'lib/sequel/lib/sequel/sql.rb', line 447

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 StringExpression, NumericExpression
    raise(Sequel::Error, "cannot invert #{ce.inspect}")
  else
    BooleanExpression.new(:NOT, ce)
  end
end