UNDEF => sub { # CASE: col => {op => undef} : sql "IS (NOT)? NULL"
my $is =
- $op =~ $self->{equality_op} ? 'is'
+ $op =~ /^not$/i ? 'is not' # legacy
+ : $op =~ $self->{equality_op} ? 'is'
: $op =~ $self->{like_op} ? belch("Supplying an undefined argument to '@{[ uc $op]}' is deprecated") && 'is'
: $op =~ $self->{inequality_op} ? 'is not'
: $op =~ $self->{not_like_op} ? belch("Supplying an undefined argument to '@{[ uc $op]}' is deprecated") && 'is not'