From 9850c76d4fa6de7f2866d08a348e170932d8aa77 Mon Sep 17 00:00:00 2001
From: Luke Vella <me@lukevella.com>
Date: Sun, 22 Dec 2024 11:48:34 +0100
Subject: [PATCH] Batch processing and error handling improvements

---
 .../migration.sql                             | 107 +++++++++++++-----
 1 file changed, 77 insertions(+), 30 deletions(-)

diff --git a/packages/database/prisma/migrations/20241218160237_create_guest_users/migration.sql b/packages/database/prisma/migrations/20241218160237_create_guest_users/migration.sql
index a737688a8..752064a61 100644
--- a/packages/database/prisma/migrations/20241218160237_create_guest_users/migration.sql
+++ b/packages/database/prisma/migrations/20241218160237_create_guest_users/migration.sql
@@ -1,51 +1,98 @@
+BEGIN;
+
 -- Create guest users for participants without user_id and link them
 DO $$
 DECLARE
-    participant_record RECORD;
+    v_processed INTEGER := 0;
+    v_total_processed INTEGER := 0;
+    v_batch_size INTEGER := 1000;
 BEGIN
-    FOR participant_record IN 
-        SELECT id, name, email 
-        FROM participants 
-        WHERE user_id IS NULL
+    RAISE NOTICE 'Starting participant migration...';
+    
+    -- Process participants in batches
     LOOP
-        WITH new_user AS (
+        WITH to_process AS (
+            SELECT id, name, email 
+            FROM participants 
+            WHERE user_id IS NULL
+            LIMIT v_batch_size
+            FOR UPDATE SKIP LOCKED
+        ),
+        new_users AS (
             INSERT INTO users (id, is_guest, created_at)
-            VALUES (
-                gen_random_uuid()::text,
-                TRUE,
-                NOW()
-            )
+            SELECT gen_random_uuid()::text, TRUE, NOW()
+            FROM to_process
             RETURNING id
         )
-        UPDATE participants
-        SET user_id = (SELECT id FROM new_user)
-        WHERE id = participant_record.id;
+        UPDATE participants p
+        SET user_id = u.id
+        FROM (
+            SELECT id, ROW_NUMBER() OVER () as rn
+            FROM new_users
+        ) u
+        WHERE p.id IN (
+            SELECT id FROM to_process
+        )
+        AND p.user_id IS NULL;
+
+        GET DIAGNOSTICS v_processed = ROW_COUNT;
+        v_total_processed := v_total_processed + v_processed;
+        
+        EXIT WHEN v_processed = 0;
+        RAISE NOTICE 'Processed % participants (total: %)', v_processed, v_total_processed;
     END LOOP;
+
+    RAISE NOTICE 'Completed participant migration. Total processed: %', v_total_processed;
 END;
-$$; 
+$$;
 
 -- Create guest users for comments without user_id and link them
 DO $$
 DECLARE
-    comment_record RECORD;
+    v_processed INTEGER := 0;
+    v_total_processed INTEGER := 0;
+    v_batch_size INTEGER := 1000;
 BEGIN
-    FOR comment_record IN 
-        SELECT id, author_name 
-        FROM comments 
-        WHERE user_id IS NULL
+    RAISE NOTICE 'Starting comment migration...';
+    
+    -- Process comments in batches
     LOOP
-        WITH new_user AS (
+        WITH to_process AS (
+            SELECT id, author_name
+            FROM comments 
+            WHERE user_id IS NULL
+            LIMIT v_batch_size
+            FOR UPDATE SKIP LOCKED
+        ),
+        new_users AS (
             INSERT INTO users (id, is_guest, created_at)
-            VALUES (
-                gen_random_uuid()::text,
-                TRUE,
-                NOW()
-            )
+            SELECT gen_random_uuid()::text, TRUE, NOW()
+            FROM to_process
             RETURNING id
         )
-        UPDATE comments
-        SET user_id = (SELECT id FROM new_user)
-        WHERE id = comment_record.id;
+        UPDATE comments c
+        SET user_id = u.id
+        FROM (
+            SELECT id, ROW_NUMBER() OVER () as rn
+            FROM new_users
+        ) u
+        WHERE c.id IN (
+            SELECT id FROM to_process
+        )
+        AND c.user_id IS NULL;
+
+        GET DIAGNOSTICS v_processed = ROW_COUNT;
+        v_total_processed := v_total_processed + v_processed;
+        
+        EXIT WHEN v_processed = 0;
+        RAISE NOTICE 'Processed % comments (total: %)', v_processed, v_total_processed;
     END LOOP;
+
+    RAISE NOTICE 'Completed comment migration. Total processed: %', v_total_processed;
+EXCEPTION WHEN OTHERS THEN
+    RAISE WARNING 'Error during comment migration: %', SQLERRM;
+    RAISE;
 END;
-$$; 
\ No newline at end of file
+$$;
+
+COMMIT; 
\ No newline at end of file