Rewrite article cleanup and update docs

docs/en/020_Getting_Started/050_Configuration.md

@@ -385,7 +385,7 @@ Arsse/0.6.0 (Linux 4.15.0; x86_64; https://thearsse.com/)
 |------------------|-----------|
 | interval or null | `"PT24H"` |
 
-How long to keep a newsfeed and its articles in the database after all its subscriptions have been deleted. Specifying `null` will retain unsubscribed newsfeeds forever, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately.
+How long to keep a newsfeed subscription and its articles in the database after it has been soft-deleted by its owner. Specifying `null` will retain unsubscribed newsfeeds forever, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately.
 
 Note that articles of orphaned newsfeeds are still subject to the `purgeArticleUnread` threshold below.
 
@@ -395,11 +395,9 @@ Note that articles of orphaned newsfeeds are still subject to the `purgeArticleU
 |------------------|---------|
 | interval or null | `"P7D"` |
 
-How long to keep a an article in the database after all users subscribed to its newsfeed have read it. Specifying `null` will retain articles up to the `purgeArticlesUnread` threshold below, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately. 
+How long to keep a an article in the database after it has been read. Specifying `null` will retain articles up to the `purgeArticlesUnread` threshold below, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately. 
 
-If an article is starred by any user, it is retained indefinitely regardless of this setting.
+If an article is starred by its owner, it is retained indefinitely regardless of this setting.
-
-This setting also governs when an article is hidden from a user after being read by that user, regardless of its actual presence in the database.
 
 ### purgeArticlesUnread
 
@@ -407,9 +405,9 @@ This setting also governs when an article is hidden from a user after being read
 |------------------|----------|
 | interval or null | `"P21D"` |
 
-How long to keep a an article in the database regardless of whether any users have read it. Specifying `null` will retain articles forever, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately. 
+How long to keep a an article in the database regardless of whether it has been read. Specifying `null` will retain articles forever, whereas an interval evaluating to zero (e.g. `"PT0S"`) will delete them immediately. 
 
-If an article is starred by any user, it is retained indefinitely regardless of this setting.
+If an article is starred by its owner, it is retained indefinitely regardless of this setting.
 
 # Obsolete settings
 

lib/Conf.php

@@ -94,10 +94,10 @@ use JKingWeb\Arsse\Misc\ValueInfo as Value;
     /** @var string|null User-Agent string to use when fetching feeds from foreign servers */
     public $fetchUserAgentString = null;
 
-    /** @var \DateInterval|null When to delete a feed from the database after all its subscriptions have been deleted, as an ISO 8601 duration (default: 24 hours; null for never)
+    /** @var \DateInterval|null When to delete a subscription from the database after it has been soft-deleted, as an ISO 8601 duration (default: 24 hours; null for never)
      * @see https://en.wikipedia.org/wiki/ISO_8601#Durations */
     public $purgeFeeds = "PT24H";
-    /** @var \DateInterval|null When to delete an unstarred article in the database after it has been marked read by all users, as an ISO 8601 duration (default: 7 days; null for never)
+    /** @var \DateInterval|null When to delete an unstarred article in the database after it has been marked read, as an ISO 8601 duration (default: 7 days; null for never)
      * @see https://en.wikipedia.org/wiki/ISO_8601#Durations */
     public $purgeArticlesRead = "P7D";
     /** @var \DateInterval|null When to delete an unstarred article in the database regardless of its read state, as an ISO 8601 duration (default: 21 days; null for never)

lib/Database.php

@@ -2043,40 +2043,18 @@ class Database {
                 from arsse_articles join (
                     SELECT article, max(id) as edition from arsse_editions group by article
                 ) as latest_editions on arsse_articles.id = latest_editions.article 
-                where feed = ? order by edition desc limit ?
+                where subscription = ? order by edition desc limit ?
-            ),
-            target_articles as (
-                SELECT 
-                    id 
-                from arsse_articles
-                join (
-                    select 
-                        feed, 
-                        count(*) as subs 
-                    from arsse_subscriptions
-                    where feed = ?
-                    group by feed
-                ) as feed_stats on feed_stats.feed = arsse_articles.feed
-                left join (
-                    select 
-                        article, 
-                        sum(case when starred = 1 and hidden = 0 then 1 else 0 end) as starred, 
-                        sum(case when \"read\" = 1 or hidden = 1 then 1 else 0 end) as \"read\", 
-                        max(arsse_marks.modified) as marked_date 
-                    from arsse_marks 
-                    group by article
-                ) as mark_stats on mark_stats.article = arsse_articles.id
-                where
-                    coalesce(starred,0) = 0 
-                    and (
-                        coalesce(marked_date,modified) <= ? 
-                        or (
-                            coalesce(\"read\",0) = coalesce(subs,0) 
-                            and coalesce(marked_date,modified) <= ?
-                        )
-                    )
             )
-            DELETE FROM arsse_articles WHERE id not in (select id from exempt_articles) and id in (select id from target_articles)",
+            DELETE FROM 
+                arsse_articles
+            where
+                subscription = ?
+                and starred = 0 
+                and (
+                    coalesce(marked,modified) <= ? 
+                    or (\"read\" = 1 and coalesce(marked,modified) <= ?)
+                )
+                and id not in (select id from exempt_articles)",
             ["int", "int", "int", "datetime", "datetime"]
         );
         $limitRead = null;
@@ -2087,11 +2065,13 @@ class Database {
         if (Arsse::$conf->purgeArticlesUnread) {
             $limitUnread = Date::sub(Arsse::$conf->purgeArticlesUnread);
         }
-        $feeds = $this->db->query("SELECT id, size from arsse_feeds")->getAll();
         $deleted = 0;
+        $tr = $this->begin();
+        $feeds = $this->db->query("SELECT id, size from arsse_subscriptions")->getAll();
         foreach ($feeds as $feed) {
             $deleted += $query->run($feed['id'], $feed['size'], $feed['id'], $limitUnread, $limitRead)->changes();
         }
+        $tr->commit();
         return (bool) $deleted;
     }