diff --git a/gossamer_forums.rb b/gossamer_forums.rb
index 2fd0996..45d5866 100644
--- a/gossamer_forums.rb
+++ b/gossamer_forums.rb
@@ -1,7 +1,7 @@
 # Federated Computer, Inc.
 # David Sainty <saint@federated.computer>  2024 A.D.
 # Gossamer Threads to Discourse -- Migration-Import Script
-# v0.40 Move to per thread MySQL/MariaDB connection
+# v0.41 Further improve FULL concurrency support, for both MySQL/MariaDB _and_ importantly, the PostGreSQL Discourse DB additions and changes with ActiveRecord connection pooling and Mutex
 
 require 'mysql2'
 require 'open-uri'
@@ -1072,16 +1072,20 @@ class GossamerForumsImporter < ImportScripts::Base
     current_post_batch = 0 # Set our current batch number. This tracks the current batch of posts being processed.
     is_complete = false # Flag to indicate whether the import process is complete.
 
+    # Mutex to control access to shared resources
+    mutex = Mutex.new
+
     # Run until all posts have been processed.
     until is_complete
       # Query in batches, create pool, wait for termination, do it again
       current_post_batch_max = current_post_batch + batch_size
 
-      ## Static pool size based on number of CPUs
-      # pool = Concurrent::FixedThreadPool.new(Concurrent.processor_count) #create thread pool that is bounded by processors avaialable, however play with the number to see what works best
+#      # Static pool size based on number of CPUs
+#      # pool = Concurrent::FixedThreadPool.new(Concurrent.processor_count) # Create a thread pool that is bounded by processors avaialable
+#      # pool = Concurrent::FixedThreadPool.new(8)                          # Create a thread pool of 8 pool members
 
       # Dynamically calculate the pool size based on system load to optimise performance
-      pool_size = calculate_dynamic_pool_size
+      pool_size = calculate_dynamic_pool_size            # Dynamically calculate what the pool size "ought" to be.
       pool = Concurrent::FixedThreadPool.new(pool_size)  # Create a thread pool with the calculated size
 
       # Process each post in the current batch
@@ -1102,19 +1106,26 @@ class GossamerForumsImporter < ImportScripts::Base
               password: "yxnh93Ybbz2Nm8#mp28zCVv",
               database: "slowtwitch"
             )
-            begin
-              puts "Processing post ID: #{post_id}"
-              topic_import_job(post_id, mysql_client)  # Import topic and its replies
-              mark_post_as_complete(post_id)  # Mark as complete in SQLite table
-            rescue => e
-              puts "Error processing post ID #{post_id}: #{e.message}"
-              mark_post_as_failed(post_id)
-            ensure
-              mysql_client.close if mysql_client
+
+            # Use connection ppoling for PostgreSQL and synchronize access to shared resources
+            ActiveRecord::Base.connection_pool.with_connection do
+              mutex.synchronize do
+                begin
+                  puts "Processing post ID: #{post_id}"
+                  topic_import_job(post_id, mysql_client)  # Import topic and its replies
+                  mark_post_as_complete(post_id)  # Mark as complete in SQLite table
+                rescue => e
+                  puts "Error processing post ID #{post_id}: #{e.message}"
+                  mark_post_as_failed(post_id)
+                ensure
+                  # Ensure the MariaDB connection is closed after processing
+                  mysql_client.close if mysql_client
+                end
+              end
             end
           end
         else
-            puts "Skipping post_id #{post_id}, already processed."
+          puts "Skipping post_id #{post_id}, already processed."
         end
 
         current_post_batch += 1  # Increment, moving to next post in the batch
@@ -1172,134 +1183,140 @@ class GossamerForumsImporter < ImportScripts::Base
   
     # Check if the topic has already been imported using the custom field 'original_gossamer_id'
     unless TopicCustomField.exists?(name: 'original_gossamer_id', value: row['post_id'])
-      # Create the new topic in Discourse
-      begin
-        suffix = 1
-        topic_created = false
-  
-        while !topic_created
-          begin
-            puts "CREATE TOPIC unique_title #{unique_title} title #{title} discourse_user_id #{discourse_user_id} category_id #{discourse_category_id}"
-            topic = Topic.create!(
-              title: unique_title,
-              user_id: discourse_user_id,
-              created_at: Time.at(row['post_time']),
-              updated_at: Time.at(row['post_time']),
-              category_id: discourse_category_id,
-              views: post_views || 0,
-              posts_count: 0
-            )
-            topic.custom_fields['original_gossamer_id'] = row['post_id']
-            topic.save!
-  
-            topic_created = true
-          rescue ActiveRecord::RecordInvalid => e
-            if e.message.include?("Title has already been used")
-              unique_title = "#{title} (#{suffix})"
-              suffix += 1
-            else
-              raise e
+      ActiveRecord::Base.transaction do
+        # Create the new topic in Discourse
+        begin
+          suffix = 1
+          topic_created = false
+    
+          while !topic_created
+            begin
+              puts "CREATE TOPIC unique_title #{unique_title} title #{title} discourse_user_id #{discourse_user_id} category_id #{discourse_category_id}"
+              topic = Topic.create!(
+                title: unique_title,
+                user_id: discourse_user_id,
+                created_at: Time.at(row['post_time']),
+                updated_at: Time.at(row['post_time']),
+                category_id: discourse_category_id,
+                views: post_views || 0,
+                posts_count: 0
+              )
+              topic.custom_fields['original_gossamer_id'] = row['post_id']
+              topic.save!
+    
+              topic_created = true
+            rescue ActiveRecord::RecordInvalid => e
+              if e.message.include?("Title has already been used")
+                unique_title = "#{title} (#{suffix})"
+                suffix += 1
+              else
+                raise e
+              end
             end
           end
-        end
+    
+          # Update the database with the last post time and user for the topic
+          update_db_topic_last_post_time(topic.id, Time.at(row['post_time']).to_i)
+          update_db_topic_last_post_user(topic.id, discourse_user_id)
+    
+          # Increment the topic count for the user
+          update_db_user_topic_count(discourse_user_id, fetch_db_user_topic_count(discourse_user_id).to_i + 1)
+    
+          # Sanitize and prepare the post message for Discourse
+          sanitized_post_message = sanitize_post_message(row['post_message'])
+    
+          puts "CREATE POST topic.id #{topic.id} discourse_user_id #{discourse_user_id}"
+    
+          # Increment the post count for the topic
+          post_number = fetch_db_topic_post_numbers(topic.id).to_i + 1
+          update_db_topic_post_numbers(topic.id, post_number)
   
-        # Update the database with the last post time and user for the topic
-        update_db_topic_last_post_time(topic.id, Time.at(row['post_time']).to_i)
-        update_db_topic_last_post_user(topic.id, discourse_user_id)
-  
-        # Increment the topic count for the user
-        update_db_user_topic_count(discourse_user_id, fetch_db_user_topic_count(discourse_user_id).to_i + 1)
-  
-        # Sanitize and prepare the post message for Discourse
-        sanitized_post_message = sanitize_post_message(row['post_message'])
-  
-        puts "CREATE POST topic.id #{topic.id} discourse_user_id #{discourse_user_id}"
-  
-        # Increment the post count for the topic
-        post_number = fetch_db_topic_post_numbers(topic.id).to_i + 1
-        update_db_topic_post_numbers(topic.id, post_number)
-  
-        # Create the initial post in the new topic
-        post = Post.create!(
-          topic_id: topic.id,
-          user_id: discourse_user_id,
-          raw: sanitized_post_message,
-          created_at: Time.at(row['post_time']),
-          updated_at: Time.at(row['post_time']),
-          reads: post_views || 0,
-          post_number: post_number
-        )
-        post.custom_fields['original_gossamer_id'] = row['post_id']
-        post.save!
-  
-        # Increment the post count for the topic and user
-        update_db_topic_post_count(topic.id, fetch_db_topic_post_count(topic.id).to_i + 1)
-        update_db_user_post_count(discourse_user_id, fetch_db_user_post_count(discourse_user_id).to_i + 1)
-  
-        # Handle any attachments associated with the post
-        handle_post_attachments(row['post_id'], post, discourse_user_id)
-  
-        # Create URL mappings for the new topic
-        new_url = "https://new/t/#{topic.slug}/#{topic.id}"
-        insert_url_mapping(row['post_id'], new_url, unique_title)
-  
-        # Now fetch and import all replies to this topic
-        replies = execute_query("SELECT post_id, user_id_fk, post_message, post_time, FROM gforum_Post WHERE post_root_id = #{post_id} ORDER BY post_time ASC")
-  
-        # Import each reply sequentially
-        replies.each do |reply_row|
-          begin
-            # Fetch the discourse user ID for the reply
-            reply_user_id = fetch_user_id_mapping(reply_row['user_id_fk'])
-  
-            # Sanitize and prepare the reply message for Discourse
-            sanitized_reply_message = sanitize_post_message(reply_row['post_message'])
-  
-            puts "CREATE REPLY in topic_id #{topic.id}"
-  
-            # Increment the post count for the topic
-            post_number = fetch_db_topic_post_numbers(topic.id).to_i + 1
-            update_db_topic_post_numbers(topic.id, post_number)
-  
-            # Create the reply post in the existing topic
-            post = Post.create!(
-              topic_id: topic.id,
-              user_id: reply_user_id,
-              raw: sanitized_reply_message,
-              created_at: Time.at(reply_row['post_time']),
-              updated_at: Time.at(reply_row['post_time']),
-              post_number: post_number
-            )
-            post.custom_fields['original_gossamer_id'] = reply_row['post_id']
-            post.save!
-  
-            # Increment the post count for the topic and user
-            update_db_topic_post_count(topic.id, fetch_db_topic_post_count(topic.id).to_i + 1)
-            update_db_user_post_count(reply_user_id, fetch_db_user_post_count(reply_user_id).to_i + 1)
-  
-            # Update last post time and user for the topic
-            if fetch_db_topic_last_post_time(topic.id).nil? || Time.at(reply_row['post_time']).to_i > fetch_db_topic_last_post_time(topic.id).to_i
-              update_db_topic_last_post_time(topic.id, Time.at(reply_row['post_time']).to_i)
-              update_db_topic_last_post_user(topic.id, reply_user_id)
+          # Create the initial post in the new topic
+          post = Post.create!(
+            topic_id: topic.id,
+            user_id: discourse_user_id,
+            raw: sanitized_post_message,
+            created_at: Time.at(row['post_time']),
+            updated_at: Time.at(row['post_time']),
+            reads: post_views || 0,
+            post_number: post_number
+          )
+          post.custom_fields['original_gossamer_id'] = row['post_id']
+          post.save!
+    
+          # Increment the post count for the topic and user
+          update_db_topic_post_count(topic.id, fetch_db_topic_post_count(topic.id).to_i + 1)
+          update_db_user_post_count(discourse_user_id, fetch_db_user_post_count(discourse_user_id).to_i + 1)
+    
+          # Handle any attachments associated with the post
+          handle_post_attachments(row['post_id'], post, discourse_user_id)
+    
+          # Create URL mappings for the new topic
+          new_url = "https://new/t/#{topic.slug}/#{topic.id}"
+          insert_url_mapping(row['post_id'], new_url, unique_title)
+    
+          # Fetch and import all replies to this topic
+          replies = execute_query("SELECT post_id, user_id_fk, post_message, post_time, FROM gforum_Post WHERE post_root_id = #{post_id} ORDER BY post_time ASC")
+    
+          # Import each reply sequentially
+          replies.each do |reply_row|
+            begin
+              # Fetch the discourse user ID for the reply
+              reply_user_id = fetch_user_id_mapping(reply_row['user_id_fk'])
+    
+              # Sanitize and prepare the reply message for Discourse
+              sanitized_reply_message = sanitize_post_message(reply_row['post_message'])
+    
+              puts "CREATE REPLY in topic_id #{topic.id}"
+    
+              # Increment the post count for the topic
+              post_number = fetch_db_topic_post_numbers(topic.id).to_i + 1
+              update_db_topic_post_numbers(topic.id, post_number)
+    
+              # Create the reply post in the existing topic
+              post = Post.create!(
+                topic_id: topic.id,
+                user_id: reply_user_id,
+                raw: sanitized_reply_message,
+                created_at: Time.at(reply_row['post_time']),
+                updated_at: Time.at(reply_row['post_time']),
+                post_number: post_number
+              )
+              post.custom_fields['original_gossamer_id'] = reply_row['post_id']
+              post.save!
+    
+              # Increment the post count for the topic and user
+              update_db_topic_post_count(topic.id, fetch_db_topic_post_count(topic.id).to_i + 1)
+              update_db_user_post_count(reply_user_id, fetch_db_user_post_count(reply_user_id).to_i + 1)
+    
+              # Update last post time and user for the topic
+              if fetch_db_topic_last_post_time(topic.id).nil? || Time.at(reply_row['post_time']).to_i > fetch_db_topic_last_post_time(topic.id).to_i
+                update_db_topic_last_post_time(topic.id, Time.at(reply_row['post_time']).to_i)
+                update_db_topic_last_post_user(topic.id, reply_user_id)
+              end
+    
+              # Handle any attachments associated with the reply
+              handle_post_attachments(reply_row['post_id'], post, reply_user_id)
+    
+#             # Update the highest processed post_id in the database (thread-safe)
+#             update_highest_processed_post_id_thread_safe(reply_row['post_id'])
+    
+#            rescue ActiveRecord::RecordInvalid => e
+            rescue => e
+              puts "Error importing reply with post_id #{reply_row['post_id']}: #{e.message}"
             end
-  
-            # Handle any attachments associated with the reply
-            handle_post_attachments(reply_row['post_id'], post, reply_user_id)
-  
-#            # Update the highest processed post_id in the database (thread-safe)
-#            update_highest_processed_post_id_thread_safe(reply_row['post_id'])
-  
-          rescue ActiveRecord::RecordInvalid => e
-            puts "Error importing reply with post_id #{reply_row['post_id']}: #{e.message}"
           end
+  
+#          # After processing the entire topic, update the highest_processed_post_id to the current topic's post_id (thread-safe)
+#          update_highest_processed_post_id_thread_safe(post_id)
+    
+        rescue ActiveRecord::RecordInvalid => e
+          puts "Error importing topic with post_id #{row['post_id']}: #{e.message}"
+          raise ActiveRecord::Rollback
         end
-  
-#        # After processing the entire topic, update the highest_processed_post_id to the current topic's post_id (thread-safe)
-#        update_highest_processed_post_id_thread_safe(post_id)
-  
-      rescue ActiveRecord::RecordInvalid => e
-        puts "Error importing topic with post_id #{row['post_id']}: #{e.message}"
       end
+    else
+      puts "Topic for post_id #{row['post_id']} already exists, skipping creation."
     end
   end