From 44eba0bb608d2cef9651cc25eeb06e3e8841ee7d Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Thu, 18 Oct 2018 10:52:45 +0800
Subject: [PATCH] FIX: Don't rescue `PG::UniqueViolation` within a transaction.

Also acquire a transaction per link instead of failing when
any of the links can't be processed.

This prevents ActiveRecord from rolling back the transaction
and the next SQL statement sent to PG will fail. This is
however hard to test as it only happens when there are
two competing process trying to process this method at the
same time.
---
 app/models/topic_link.rb | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/app/models/topic_link.rb b/app/models/topic_link.rb
index 22f8feeab73..229e2eb835a 100644
--- a/app/models/topic_link.rb
+++ b/app/models/topic_link.rb
@@ -112,24 +112,23 @@ SQL
     return if post.blank? || post.whisper?
 
     added_urls = []
-    TopicLink.transaction do
+    reflected_ids = []
 
-      added_urls = []
-      reflected_ids = []
-
-      PrettyText
-        .extract_links(post.cooked)
-        .map do |u|
-          uri = begin
-            URI.parse(u.url)
-          rescue URI::Error
-          end
-
-          [u, uri]
+    PrettyText
+      .extract_links(post.cooked)
+      .map do |u|
+        uri = begin
+          URI.parse(u.url)
+        rescue URI::Error
         end
-        .reject { |_, p| p.nil? || "mailto".freeze == p.scheme }
-        .uniq { |_, p| p }
-        .each do |link, parsed|
+
+        [u, uri]
+      end
+      .reject { |_, p| p.nil? || "mailto".freeze == p.scheme }
+      .uniq { |_, p| p }
+      .each do |link, parsed|
+
+      TopicLink.transaction do
         begin
           url = link.url
           internal = false
@@ -185,7 +184,7 @@ SQL
                                 link_post_id: reflected_post.try(:id),
                                 quote: link.is_quote,
                                 extension: file_extension)
-            rescue ActiveRecord::RecordNotUnique, PG::UniqueViolation
+            rescue ActiveRecord::RecordNotUnique
               # it's fine
             end
           end