PERF: avoid lookbehinds when indexing search (#10862)

* PERF: avoid lookbehinds when indexing search

Previously we used a `EmailCook.url_regexp` this regex used lookbehinds

Unfortunately certain strings could lead to pathological behavior causing
CPU to skyrocket and regex replace to take a very very long time.

EmailCook still needs a fix, but it is less urgent cause it already splits
to single lines. That said we will correct that as well in a seperate PR.

New implementation is far more naive and relies on the extra spaces search
indexer inserts.

lib/search.rb

@@ -88,12 +88,17 @@ class Search
       end
     end
 
-    data.gsub!(EmailCook.url_regexp) do |url|
-      uri = URI.parse(url)
+    data.gsub!(/\S+/) do |str|
+      if str.match?(/^(https?:\/\/)[\S]+$/)
+        begin
+          uri = URI.parse(str)
           uri.query = nil
-      uri.to_s
+          str = uri.to_s
         rescue URI::Error
-      # Don't fail even if URL turns out to be invalid
+          # don't fail if uri does not parse
+        end
+      end
+      str
     end
 
     data

spec/services/search_indexer_spec.rb

@@ -158,7 +158,6 @@ describe SearchIndexer do
 
       post.rebake!
       post.reload
-      topic = post.topic
 
       expect(post.post_search_data.raw_data).to eq(
         "https://meta.discourse.org/some.png"
@@ -189,19 +188,25 @@ describe SearchIndexer do
       topic = Fabricate(:topic, category: category, title: 'this is a test topic')
 
       post = Fabricate(:post, topic: topic, raw: <<~RAW)
-      a https://cnn.com?bob=1, http://stuff.com.au?bill=1 b abc.net/xyz=1
+      a https://abc.com?bob=1, http://efg.com.au?bill=1 b hij.net/xyz=1
+      www.klm.net/?IGNORE=1 <a href="http://abc.de.nop.co.uk?IGNORE=1&ingore2=2">test</a>
       RAW
 
       post.rebake!
       post.reload
       topic = post.topic
 
+      # Note, a random non URL string should be tokenized properly,
+      # hence www.klm.net?IGNORE=1 it was inserted in autolinking.
+      # We could consider amending the auto linker to add
+      # more context to say "hey, this part of <a href>...</a> was a guess by autolinker.
+      # A blanket treating of non-urls without this logic is risky.
       expect(post.post_search_data.raw_data).to eq(
-        "a https://cnn.com , http://stuff.com.au b http://abc.net/xyz=1 abc.net/xyz=1"
+        "a https://abc.com , http://efg.com.au b http://hij.net/xyz=1 hij.net/xyz=1 http://www.klm.net/ www.klm.net/?IGNORE=1 http://abc.de.nop.co.uk test"
       )
 
       expect(post.post_search_data.search_data).to eq(
-        "'/xyz=1':14,17 'abc.net':13,16 'abc.net/xyz=1':12,15 'au':10 'awesom':6B 'b':11 'categori':7B 'cnn.com':9 'com':9 'com.au':10 'net':13,16 'stuff.com.au':10 'test':4A 'topic':5A"
+        "'/?ignore=1':21 '/xyz=1':14,17 'abc.com':9 'abc.de.nop.co.uk':22 'au':10 'awesom':6B 'b':11 'categori':7B 'co.uk':22 'com':9 'com.au':10 'de.nop.co.uk':22 'efg.com.au':10 'hij.net':13,16 'hij.net/xyz=1':12,15 'klm.net':18,20 'net':13,16,18,20 'nop.co.uk':22 'test':4A,23 'topic':5A 'uk':22 'www.klm.net':18,20 'www.klm.net/?ignore=1':19"
       )
     end
 
@@ -222,7 +227,6 @@ describe SearchIndexer do
 
       post.rebake!
       post.reload
-      topic = post.topic
 
       expect(post.cooked).to include(
         CookedPostProcessor::LIGHTBOX_WRAPPER_CSS_CLASS
@@ -235,7 +239,7 @@ describe SearchIndexer do
 
     it 'should strips audio and videos URLs from raw data' do
       SiteSetting.authorized_extensions = 'mp4'
-      upload = Fabricate(:video_upload)
+      Fabricate(:video_upload)
 
       post.update!(raw: <<~RAW)
       link to an external page: https://google.com/?u=bar