在 PostgreSql 中批量更新和删除哪个效率更高？

Question

In my java web application, I need to delete a set of records from a table. I have 2 options:

1. Directly run delete query from the application
2. Update a value in all the records to hide them from the user view and let a daemon thread run and clean up these records in the background.

The number of records can range from 10 to 100000. My intent here is to know the efficient and safe way to do that without putting too much load on the server.

PS: Feel free to share any other suitable approach.

Answer 1

Under the hood, an UPDATE is actually:

1. Flag updated row as deleted
2. Insert new row, which is a copy of the row in 1. above, but reflecting updated columns

Therefore, since an UPDATE operation involves two writes, a DELETE is actually more efficient, as it simply flags the deleted row, using one write (because of the Multi-Version Concurrency Control (MVCC) framework)

Disclosure: I work for EnterpriseDB (EDB)

Answer 2

Update command takes much more time as compared to delete command. In the update, you are actually making a copy of the data and the old version of the data is just hidden from the view.

Answer 3

If you require these records in the future, you can move these records in another table.

The advantage of this approach are:-

1. You are not overloading your current table, Hence all operations for this table will be fast.
2. You can use these records in the future.

Update

As you don't need the records and as update is more expensive then delete you should issue a delete call in batches of let say 500 to 5000 records.