From d7499f74c9eed7cebb6a4e273f04c854c1674c06 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@yhbt.net>
Date: Wed, 10 Jun 2020 07:05:17 +0000
Subject: imap: remove non-UID SEARCH for now

Supporting MSNs in long-lived connections beyond the lifetime of
a single request/response cycle is not scalable to a C10K
scenario.  It's probably not needed, since most clients seem to
use UIDs.

A somewhat efficient implementation I can come up uses
pack("S*" ...) (AKA "uint16_t mapping[50000]") has an overhead
of 100K per-client socket on a mailbox with 50K messages.  The
100K is a contiguous scalar, so it could be swapped out for
idle clients on most architectures if THP is disabled.

An alternative could be to use a tempfile as an allocator
partitioned into 100K chunks (or SQLite); but I'll only do that
if somebody presents a compelling case to support MSN SEARCH.
---
 lib/PublicInbox/IMAP.pm | 33 +++++++++------------------------
 1 file changed, 9 insertions(+), 24 deletions(-)

(limited to 'lib')

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 1ba3a3ff..7efe5387 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -986,21 +986,14 @@ sub parse_date ($) { # 02-Oct-1993
 	timegm(0, 0, 0, $dd, $mm, $yyyy);
 }
 
-sub msn_convert ($$) {
-	my ($self, $uids) = @_;
-	my $adj = $self->{uid_base};
-	$_ -= $adj for @$uids;
-}
-
 sub search_uid_range { # long_response
-	my ($self, $tag, $sql, $range_info, $want_msn) = @_;
+	my ($self, $tag, $sql, $range_info) = @_;
 	my $uids = [];
 	if (defined(my $err = refill_uids($self, $uids, $range_info, $sql))) {
 		$err ||= 'OK Search done';
 		$self->write("\r\n$tag $err\r\n");
 		return;
 	}
-	msn_convert($self, $uids) if $want_msn;
 	$self->msg_more(join(' ', '', @$uids));
 	1; # more
 }
@@ -1162,46 +1155,38 @@ sub refill_xap ($$$$) {
 }
 
 sub search_xap_range { # long_response
-	my ($self, $tag, $q, $range_info, $want_msn) = @_;
+	my ($self, $tag, $q, $range_info) = @_;
 	my $uids = [];
 	if (defined(my $err = refill_xap($self, $uids, $range_info, $q))) {
 		$err ||= 'OK Search done';
 		$self->write("\r\n$tag $err\r\n");
 		return;
 	}
-	msn_convert($self, $uids) if $want_msn;
 	$self->msg_more(join(' ', '', @$uids));
 	1; # more
 }
 
-sub search_common {
-	my ($self, $tag, $rest, $want_msn) = @_;
+sub cmd_uid_search ($$$;) {
+	my ($self, $tag) = splice(@_, 0, 2);
 	my $ibx = $self->{ibx} or return "$tag BAD No mailbox selected\r\n";
-	my $q = parse_query($self, $rest);
+	my $q = parse_query($self, \@_);
 	return "$tag $q\r\n" if !ref($q);
 	my ($sql, $range_info) = delete @$q{qw(sql range_info)};
 	if (!scalar(keys %$q)) { # overview.sqlite3
 		$self->msg_more('* SEARCH');
 		long_response($self, \&search_uid_range,
-				$tag, $sql, $range_info, $want_msn);
+				$tag, $sql, $range_info);
 	} elsif ($q = $q->{xap}) {
 		$self->msg_more('* SEARCH');
 		long_response($self, \&search_xap_range,
-				$tag, $q, $range_info, $want_msn);
+				$tag, $q, $range_info);
 	} else {
 		"$tag BAD Error\r\n";
 	}
 }
 
-sub cmd_uid_search ($$$;) {
-	my ($self, $tag) = splice(@_, 0, 2);
-	search_common($self, $tag, \@_);
-}
-
-sub cmd_search ($$$;) {
-	my ($self, $tag) = splice(@_, 0, 2);
-	search_common($self, $tag, \@_, 1);
-}
+# note: MSN SEARCH is NOT supported.  Do any widely-used MUAs
+# rely on MSNs from SEARCH results?  Let us know at meta@public-inbox.org
 
 sub args_ok ($$) { # duplicated from PublicInbox::NNTP
 	my ($cb, $argc) = @_;
-- 
cgit v1.2.3-24-ge0c7