From 4d8b04cda93b0c2397a7544b9575dee3681fc085 Mon Sep 17 00:00:00 2001
From: Alexei Sorokin <sor.alexei@meowr.ru>
Date: Mon, 21 Sep 2020 22:25:33 +0300
Subject: [PATCH] Clear out potential duplicates when semi-joining a union

Using a left outer join as a semi-join is not a valid approach.
Can still be used for an anti-semi-join.
---
 classes/Memcached_DataObject.php              |  6 +-----
 lib/notices/inboxnoticestream.php             |  2 +-
 plugins/Autocomplete/actions/autocomplete.php | 14 +++++++-------
 3 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/classes/Memcached_DataObject.php b/classes/Memcached_DataObject.php
index 6cb60e3802..d2140e3497 100644
--- a/classes/Memcached_DataObject.php
+++ b/classes/Memcached_DataObject.php
@@ -128,7 +128,7 @@ class Memcached_DataObject extends Safe_DataObject
         $join_tablename = common_database_tablename(
             $obj->tableName() . '_vals'
         );
-        $join_keyword = ($preserve ? 'RIGHT' : 'LEFT') . ' JOIN';
+        $join_keyword = ($preserve ? 'RIGHT' : 'INNER') . ' JOIN';
         $vals_cast_type = ($col_type === 'int') ? 'INTEGER' : 'TEXT';
 
         // A lot of magic to ensure we get an ordered reply with the same exact
@@ -179,10 +179,6 @@ class Memcached_DataObject extends Safe_DataObject
                 );
         }
 
-        if (!$preserve) {
-            // Implements a left semi-join
-            $obj->whereAdd("{$join_tablename}.{$keyCol}_pos IS NOT NULL");
-        }
         // Filters both NULLs requested and non-matching NULLs
         if ($skipNulls) {
             $obj->whereAdd("{$obj->escapedTableName()}.{$keyCol} IS NOT NULL");
diff --git a/lib/notices/inboxnoticestream.php b/lib/notices/inboxnoticestream.php
index 3f48b6a3bb..7293b14c30 100644
--- a/lib/notices/inboxnoticestream.php
+++ b/lib/notices/inboxnoticestream.php
@@ -126,7 +126,7 @@ class RawInboxNoticeStream extends FullNoticeStream
         // managed to post here.
         $notice->query(sprintf(
             <<<'END'
-            SELECT id
+            SELECT DISTINCT id
               FROM (
                 (
                   SELECT notice.id
diff --git a/plugins/Autocomplete/actions/autocomplete.php b/plugins/Autocomplete/actions/autocomplete.php
index 37014c99b9..0c79b06c21 100644
--- a/plugins/Autocomplete/actions/autocomplete.php
+++ b/plugins/Autocomplete/actions/autocomplete.php
@@ -97,8 +97,8 @@ class AutocompleteAction extends Action
         $this->groups = [];
         $this->profiles = [];
         $term = $this->arg('term');
-        $limit = $this->arg('limit');
-        // prevent DOS attacks
+        $limit = (int) $this->arg('limit');
+        // Prevent DOS attacks
         if ($limit > 200) {
             $limit = 200;
         }
@@ -109,17 +109,17 @@ class AutocompleteAction extends Action
             $profile = new Profile();
             $profile->_join .= sprintf(
                 "\n" . <<<'END'
-                LEFT JOIN (
+                INNER JOIN (
                   SELECT id FROM %s
-                  UNION ALL
+                  UNION
                   SELECT subscribed AS id FROM subscription WHERE subscriber = %d
                 ) AS t1 USING (id)
                 END,
                 $user_table,
                 $this->scoped->id
             );
-            $profile->whereAdd('t1.id IS NOT NULL');
             $profile->whereAdd('nickname LIKE \'' . trim($profile->escape($term), '\'') . '%\'');
+            $profile->orderBy('created, id');
             $profile->limit($limit);
 
             if ($profile->find()) {
@@ -127,8 +127,7 @@ class AutocompleteAction extends Action
                     $this->profiles[] = clone($profile);
                 }
             }
-        }
-        if (substr($term, 0, 1) === '!') {
+        } elseif (substr($term, 0, 1) === '!') {
             //group search
             $term = substr($term, 1);
             $group = new User_group();
@@ -138,6 +137,7 @@ class AutocompleteAction extends Action
                 $this->scoped->id
             ));
             $group->whereAdd('nickname LIKE \'' . trim($group->escape($term), '\'') . '%\'');
+            $group->orderBy('created, id');
             $group->limit($limit);
 
             if ($group->find()) {