Subclass of ComplexExpression
where the expression results in
a boolean value in SQL.
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
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)
# File lib/sequel/sql.rb, line 887 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 NegativeBooleanConstant new(:"IS NOT", l, r.constant) when BooleanConstant new(:IS, l, r.constant) 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 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"
# File lib/sequel/sql.rb, line 916 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}") when Constant CONSTANT_INVERSIONS[ce] || raise(Sequel::Error, "cannot invert #{ce.inspect}") else BooleanExpression.new(:NOT, ce) end end
Always use an AND operator for & on BooleanExpressions
# File lib/sequel/sql.rb, line 935 def &(ce) BooleanExpression.new(:AND, self, ce) end
Return self instead of creating a new object to save on memory.
# File lib/sequel/sql.rb, line 945 def sql_boolean self end
Always use an OR operator for | on BooleanExpressions
# File lib/sequel/sql.rb, line 940 def |(ce) BooleanExpression.new(:OR, self, ce) end