[PATCH 4/5] searchidx: use Perl truthiness to detect XAPIAN_FLUSH_THRESHOLD

[Eric Wong <e@yhbt.net>]

XAPIAN_FLUSH_THRESHOLD is a C string in the environment, so
users may be tempted to assign an empty string in in their
shell, e.g. `XAPIAN_FLUSH_THRESHOLD= <command>' instead of using
`unset' POSIX shell built-in.

With either a value of "0" or "" (empty string), Xapian will
fall back to its default (10000 documents), which causes grief
for memory-starved users.
---
 lib/PublicInbox/SearchIdx.pm | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 22489731..01b9f52d 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -25,8 +25,7 @@ our @EXPORT_OK = qw(crlf_adjust log2stack is_ancestor check_size nodatacow_dir);
 my $X = \%PublicInbox::Search::X;
 my ($DB_CREATE_OR_OPEN, $DB_OPEN);
 our $DB_NO_SYNC = 0;
-our $BATCH_BYTES = defined($ENV{XAPIAN_FLUSH_THRESHOLD}) ?
-			0x7fffffff : 1_000_000;
+our $BATCH_BYTES = $ENV{XAPIAN_FLUSH_THRESHOLD} ? 0x7fffffff : 1_000_000;
 use constant DEBUG => !!$ENV{DEBUG};
 
 my $xapianlevels = qr/\A(?:full|medium)\z/;