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authorEric Wong (Contractor, The Linux Foundation) <e@80x24.org>2018-04-02 00:04:56 +0000
committerEric Wong (Contractor, The Linux Foundation) <e@80x24.org>2018-04-02 00:05:43 +0000
commit5a44b89fd9f4ef2688b91262736b0f61095ae99c (patch)
treef5b3937f387679d277f617cbfeb6c7dc75fac717
parent87dca6d8d5988c5eb54019cca342450b0b7dd6b7 (diff)
downloadpublic-inbox-5a44b89fd9f4ef2688b91262736b0f61095ae99c.tar.gz
JOIN operations on SQLite can be disasterously slow.
This reduces per-message pages with the thread overview
at the bottom of those pages from over 800ms to ~60ms.
In comparison, the v1 code took around 70-80ms using
Xapian on my machine.
-rw-r--r--lib/PublicInbox/Over.pm27
1 files changed, 19 insertions, 8 deletions
diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index c74072a2..3d285ac2 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -73,20 +73,31 @@ ORDER BY ts ASC
 
 }
 
+sub nothing () { wantarray ? (0, []) : [] };
+
 sub get_thread {
         my ($self, $mid, $opts) = @_;
         my $dbh = $self->connect;
-        my ($tid, $sid) = $dbh->selectrow_array(<<'', undef, $mid);
-SELECT tid,sid FROM over
-LEFT JOIN id2num ON over.num = id2num.num
-LEFT JOIN msgid ON id2num.id = msgid.id
-WHERE msgid.mid = ? AND over.num > 0
-LIMIT 1
+
+        my $id = $dbh->selectrow_array(<<'', undef, $mid);
+SELECT id FROM msgid WHERE mid = ? LIMIT 1
+
+        defined $id or return nothing;
+
+        my $num = $dbh->selectrow_array(<<'', undef, $id);
+SELECT num FROM id2num WHERE id = ? AND num > 0
+ORDER BY num ASC LIMIT 1
+
+        defined $num or return nothing;
+
+        my ($tid, $sid) = $dbh->selectrow_array(<<'', undef, $num);
+SELECT tid,sid FROM over WHERE num = ? LIMIT 1
+
+        defined $tid or return nothing; # $sid may be undef
 
         my $cond = 'FROM over WHERE (tid = ? OR sid = ?) AND num > 0';
         my $msgs = do_get($self, <<"", $opts, $tid, $sid);
-SELECT * $cond
-ORDER BY ts ASC
+SELECT * $cond ORDER BY ts ASC
 
         return $msgs unless wantarray;