Fix article tagging

A commit a long time ago removed the tags column from articles and replaced it with
the taggings table, but it looks like the code to rename and delete tags, and also
to show all tagged articles was broken.

This fixes all of the references to the old tags column and switches them to
reference taggings instead. I also inlined the all-tags subquery.

This should fix #840

Author: brendanlong

src/DataBaseReadOnly.vala

@@ -810,16 +810,9 @@ public Tag? read_tag(string tagID)
 		row[3].to_int());
 }
 
-// FIXME: Inline this as a subquery
 protected string getAllTagsCondition()
 {
-	var tags = read_tags();
-	var conditions = new Gee.ArrayList<string>();
-	foreach(Tag tag in tags)
-	{
-		conditions.add("instr(\"tags\", %s) > 0".printf(SQLite.quote_string(tag.getTagID())));
-	}
-	return "(%s)".printf(StringUtils.join(conditions, " OR "));
+	return "articleID IN (SELECT articleID FROM taggings WHERE instr(tagID, 'global.') = 0)";
 }
 
 public Gee.List<Category> read_categories_level(int level, Gee.List<Feed>? feeds = null)

src/DataBaseWriteAccess.vala

@@ -112,18 +112,7 @@ private void delete_article(string articleID, string feedID)
 public void dropTag(Tag tag)
 {
 	m_db.execute("DELETE FROM main.tags WHERE tagID = ?", { tag.getTagID() });
-
-	var rows = m_db.execute("SELECT tags, articleID FROM main.articles WHERE instr(tags, ?) > 0", { tag.getTagID() });
-	foreach(var row in rows)
-	{
-		string articleID = row[1].to_string();
-		Gee.List<string> tags = StringUtils.split(row[0].to_string(), ",", true);
-		if(tags.contains(tag.getTagID()))
-			tags.remove(tag.getTagID());
-
-		m_db.execute("UPDATE main.articles SET tags = ? WHERE articleID = ?",
-		             { StringUtils.join(tags, ","), articleID });
-	}
+	m_db.execute("DELETE FROM main.taggings WHERE tagID = ?",  { tag.getTagID() });
 }
 
 public void write_feeds(Gee.Collection<Feed> feeds)
@@ -217,8 +206,6 @@ public void update_tag(Tag tag)
 	{
 		string newID = tag.getTagID().replace(tag.getTitle(), tag.getTitle());
 		m_db.execute("UPDATE tags SET tagID = ? WHERE tagID = ?", { newID, tag.getTagID() });
-		m_db.execute("UPDATE articles SET tags = replace(tags, ?, ?) WHERE instr(tags,  ?)",
-		             { tag.getTagID(), newID, tag.getTagID() });
 	}
 }