Magento 升级需要很长时间并且永远不会完成

Fix: I found from pdo_mysql.log file that the issue is in the sales_flat_order table, which means many duplicate entries for primary key are there so I truncate all the sales tables. This is actually the error in my old DB. In new version increment_id is UNIQUE. We can't skip primary key checks, so I truncated all the tables related to sales. If you have same issue then truncate all tables related to that feature like if duplicate in customer then truncate all customer table or if in catalog then truncate catalog tables. But remember truncate should be done at the time when the error is occured because if truncated before the installation begins the installer will not read the existing data and finally you will miss some records like missing some orders or invoices.

SET FOREIGN_KEY_CHECKS = 0;
TRUNCATE `sales_flat_creditmemo`;
TRUNCATE `sales_flat_creditmemo_comment`;
TRUNCATE `sales_flat_creditmemo_grid`;
TRUNCATE `sales_flat_creditmemo_item`;
TRUNCATE `sales_flat_invoice`;
TRUNCATE `sales_flat_invoice_comment`;
TRUNCATE `sales_flat_invoice_grid`;
TRUNCATE `sales_flat_invoice_item`;
TRUNCATE `sales_flat_order`;
TRUNCATE `sales_flat_order_address`;
TRUNCATE `sales_flat_order_grid`;
TRUNCATE `sales_flat_order_item`;
TRUNCATE `sales_flat_order_payment`;
TRUNCATE `sales_flat_order_status_history`;
TRUNCATE `sales_flat_quote`;
TRUNCATE `sales_flat_quote_address`;
TRUNCATE `sales_flat_quote_address_item`;
TRUNCATE `sales_flat_quote_item`;
TRUNCATE `sales_flat_quote_item_option`;
TRUNCATE `sales_flat_quote_payment`;
TRUNCATE `sales_flat_quote_shipping_rate`;
TRUNCATE `sales_flat_shipment`;
TRUNCATE `sales_flat_shipment_comment`;
TRUNCATE `sales_flat_shipment_grid`;
TRUNCATE `sales_flat_shipment_item`;
TRUNCATE `sales_flat_shipment_track`;
SET FOREIGN_KEY_CHECKS = 1;