class Sequel::SQL::BooleanExpression

  1. lib/sequel/sql.rb
Superclass: ComplexExpression

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

Methods

Public Class

  1. from_value_pairs
  2. invert

Public Instance

  1. &
  2. sql_boolean
  3. |

Included modules

  1. BooleanMethods

Public Class methods

from_value_pairs (pairs, op=:AND, negate=false)

Take pairs of values (e.g. a hash or array of two element arrays) 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

true

left IS TRUE

false

left IS FALSE

/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)
[show source]
     # File lib/sequel/sql.rb
1081 def self.from_value_pairs(pairs, op=:AND, negate=false)
1082   pairs = pairs.map{|l,r| from_value_pair(l, r)}
1083   pairs.map!{|ce| invert(ce)} if negate
1084   pairs.length == 1 ? pairs[0] : new(op, *pairs)
1085 end
invert (ce)

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).

BooleanExpression.invert(:a) # NOT "a"
[show source]
     # File lib/sequel/sql.rb
1140 def self.invert(ce)
1141   case ce
1142   when BooleanExpression
1143     case op = ce.op
1144     when :AND, :OR
1145       BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.map{|a| BooleanExpression.invert(a)})
1146     when :IN, :"NOT IN"
1147       BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
1148     else
1149       if ce.args.length == 2
1150         case ce.args[1]
1151         when Function, LiteralString, PlaceholderLiteralString
1152           # Special behavior to not push down inversion in this case because doing so
1153           # can result in incorrect behavior for ANY/SOME/ALL operators.
1154           BooleanExpression.new(:NOT, ce)
1155         else
1156           BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
1157         end
1158       else
1159         BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
1160       end
1161     end
1162   when StringExpression, NumericExpression
1163     raise(Sequel::Error, "cannot invert #{ce.inspect}")
1164   when Constant
1165     CONSTANT_INVERSIONS[ce] || raise(Sequel::Error, "cannot invert #{ce.inspect}")
1166   else
1167     BooleanExpression.new(:NOT, ce)
1168   end
1169 end

Public Instance methods

& (ce)

Always use an AND operator for & on BooleanExpressions

[show source]
     # File lib/sequel/sql.rb
1172 def &(ce)
1173   BooleanExpression.new(:AND, self, ce)
1174 end
sql_boolean ()

Return self instead of creating a new object to save on memory.

[show source]
     # File lib/sequel/sql.rb
1182 def sql_boolean
1183   self
1184 end
| (ce)

Always use an OR operator for | on BooleanExpressions

[show source]
     # File lib/sequel/sql.rb
1177 def |(ce)
1178   BooleanExpression.new(:OR, self, ce)
1179 end