disable message queueing in "save matching" mode

If only matching posts are saved, there will not be 100s of messages to save per second, they could be as rare as a few messages per day. So not only we don't want to batch them by 100, but save them immediately, but also we can't use the batch save point to save the cursor periodically either. (We'll use a separate counter instead of dividing msg.seq by 100, because with Jetstream the seq doesn't increase by 1 anymore.)

app/firehose_stream.rb

···
       @sky.on_connecting { |u| log "Connecting to #{u}..." }
 
       @sky.on_connect {
+        @message_counter = 0
         @replaying = !!(cursor)
         log "Connected ✓"
       }
···
     if @replaying
       log "Replaying events since #{msg.time.getlocal} -->"
       @replaying = false
+    end
+
+    @message_counter += 1
+
+    if @message_counter % 100 == 0
+      # save current cursor every 100 events
+      save_cursor(msg.seq)
     end
 
     msg.operations.each do |op|
···
       puts text
     end
 
-    if @save_posts == :all || @save_posts && matched
+    if @save_posts == :all
+      # wait until we have 100 posts and then save them all in one insert, if possible
       @post_queue << post
-    end
 
-    # wait until we have 100 posts and then save them all in one insert, if possible
-    if @post_queue.length >= POSTS_BATCH_SIZE
-      save_queued_posts
-      save_cursor(@sky.cursor)
+      if @post_queue.length >= POSTS_BATCH_SIZE
+        save_queued_posts
+      end
+    elsif @save_posts == :matching && matched
+      # save immediately because matched posts might be rare; we've already checked validations
+      post.save!(validate: false)
     end
 
     print '.' if @show_progress && @log_posts != :all