FLAG_PURE_NOT is too expensive for public-facing WWW use, but
lei isn't public-facing. We'll also unconditionally enable
phrase search on old "chert" DBs since lei doesn't need to
worry about fairness across 10K users.
sub qparse_new {
my ($self) = @_;
my $qp = $self->SUPER::qparse_new; # PublicInbox::Search
+ $self->{qp_flags} |= PublicInbox::Search::FLAG_PHRASE() |
+ PublicInbox::Search::FLAG_PURE_NOT();
$qp->add_boolean_prefix('kw', 'K');
$qp->add_boolean_prefix('L', 'L');
$qp