数据库加载批处理作业 Java

Question

Have a batch job written in Java which truncates and then loads certain table in Oracle database every few minutes. There are reports generated on web pages based on the data in the table. Am wondering of a good way of not affecting the report querying part when the data loading process is happeneing so that the users won't end up with some and/or no data.

Answer 1

If you process all your SQL statements inside a single transaction there will be always a valid state seen from outside. Beware that TRUNCATE doe not work in transactions, so you have to use DELETE . While this guarantees to always have reasonable data in your table it needs a bigger rollback segment and will be considerably slower.

Answer 2

you could have 2 tables and a meta table which tracks which table is the main table being used for querying. your batch job will be truncating and loading one of the table and you can switch the main tables once the loading is completed. so the query app will get recent data now and u can load now in the other table

Answer 3

What I would do is set a flag in a DB table to indicate that that the update is in progress and have the reports look for that flag and display an appropriate message and wait for the update to finish. Once the update is complete clear the flag.