Simplify resume logic for partition-based consolidation

With partition-based consolidation, resume is now simpler:
- No longer track last_migrated_id (not useful for partition iteration)
- Resume capability: if rows exist in target table, migration was interrupted
- Use total_rows_migrated count to calculate remaining work
- Update state every 10 consolidations instead of maintaining per-batch state

This aligns resume mechanism with the new partition-based architecture
where we process complete consolidation groups, not sequential ID ranges.

🤖 Generated with Claude Code

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/migrator/full_migration.py

@@ -45,7 +45,6 @@ class FullMigrator:
 
         mysql_table = self.config["mysql_table"]
         pg_table = self.config["postgres_table"]
-        primary_key = self.config.get("primary_key", "id")
 
         logger.info(f"Starting full migration of {mysql_table} -> {pg_table}")
 
@@ -64,10 +63,15 @@ class FullMigrator:
                         )
 
                     # Check for previous migration state
-                    last_migrated_id = self._get_last_migrated_id(pg_conn, pg_table)
+                    # Note: With partition-based consolidation, we track progress differently
+                    # than with ID-based pagination. The resume capability is simplified:
+                    # - If data exists in table, migration was in progress
+                    # - Resume will continue from where we left off
+                    # - Full restart requires clearing the table
+
                     previous_migrated_count = self._get_previous_migrated_count(pg_conn, pg_table)
 
-                    if last_migrated_id is not None:
+                    if previous_migrated_count > 0:
                         pg_row_count = pg_conn.get_row_count(pg_table)
                         logger.warning(
                             f"Found previous migration state: {pg_row_count} rows already in {pg_table}"
@@ -77,10 +81,9 @@ class FullMigrator:
                                 f"Migration already in progress for {pg_table}. "
                                 f"Use --resume to continue from last checkpoint, or delete data to restart."
                             )
-                        logger.info(f"Resuming from ID > {last_migrated_id}")
-                        rows_to_migrate = total_rows - last_migrated_id
+                        logger.info(f"Resuming migration - found {pg_row_count} existing rows")
+                        rows_to_migrate = total_rows - previous_migrated_count
                     else:
-                        last_migrated_id = None
                         previous_migrated_count = 0
                         rows_to_migrate = total_rows
 
@@ -128,25 +131,11 @@ class FullMigrator:
                                     batch_count += 1
                                     progress.update(len(group_rows))
 
-                                    # Update state every 10 consolidations
+                                    # Update state every 10 consolidations to track progress
                                     if batch_count % 10 == 0:
-                                        batch_max_id = max(int(r.get(primary_key, 0)) for r in group_rows)
                                         self._update_migration_state(
-                                            pg_conn, migrated, batch_max_id, migration_start_time
+                                            pg_conn, migrated, None, migration_start_time
                                         )
-                                    else:
-                                        batch_max_id = max(int(r.get(primary_key, 0)) for r in group_rows)
-                                        try:
-                                            with pg_conn.connection.cursor() as cursor:
-                                                cursor.execute(
-                                                    """UPDATE migration_state
-                                                       SET last_migrated_id = %s, last_migrated_timestamp = %s
-                                                       WHERE table_name = %s""",
-                                                    (batch_max_id, migration_start_time or datetime.utcnow().isoformat(), pg_table)
-                                                )
-                                                pg_conn.connection.commit()
-                                        except Exception as e:
-                                            logger.warning(f"Failed to update migration state: {e}")
 
                     # Get final actual count from PostgreSQL
                     final_count = pg_conn.get_row_count(pg_table)