Query performance difference pl/sql forall insert and plain SQL insert

Question

We have been using temporary table to store intermediate results in pl/sql Stored procedure. Could anyone tell if there is a performance difference between doing bulk collect in

Answer 1

It depends on the nature of the work you're doing to populate the intermediate results. If the work can be done relatively simply in the SELECT statement for the INSERT, that will generally perform better.

However, if you have some complex intermediate logic, it may be easier (from a code maintenance point of view) to fetch and insert the data in batches using bulk collects/binds. In some cases it might even be faster.

One thing to note very carefully: the query plan used by the INSERT INTO x SELECT ... will sometimes be quite different to that used when the query is run by itself (e.g. in a PL/SQL explicit cursor). When comparing performance, you need to take this into account.